US3821949A

US3821949A - Bio-feedback apparatus

Info

Publication number: US3821949A
Application number: US00242567A
Authority: US
Inventors: R Hartzell; D Albright; E Green; D Callies; W Spencer
Original assignee: MENNINGER FOUNDATION
Current assignee: MENNINGER FOUNDATION
Priority date: 1972-04-10
Filing date: 1972-04-10
Publication date: 1974-07-02
Anticipated expiration: 1991-07-02

Abstract

An improved bio-feedback apparatus for sensing the brain-wave potentials produced by a subject wherein the sensed brain-wave potentials are processed through separate parallel processing channels of a controlling channel, each processing channel processing a preselected frequency range of the sensed brain-wave potential to provide subject-preceivable feedback signals indicative of signal presence within the preselected frequency of each processing channel. Each processing channel is constructed to provide predetermined signal amplitude and duration criteria for determining signal presence prior to initiating and terminating the feedback signals and, in one form, each processing channel is constructed to provide feedback signals indicative of the percentage of time during a subsequent predetermined epoch of time wherein a signal presence existed in the sensed brain-wave potential. In one form, the bio-feedback apparatus simultaneously produces audible feedback signals, each audible feedback signal having a separately identifiable tone indicative of signal presence within the preselected frequency range of the processing channels.

Description

United States Patent [19; Hartzell et al.

[ BIO-FEEDBACK APPARATUS OTHER PUBLICATIONS Pfeiffer et al., Medical & Biological Engineering, Vol. 8, No. 2, 1970. Pp. 209-211.

Primary ExaminerWilliam E. Kamm Attorney, Agent, or Firm-Dunlap, Laney, Hessin, Dougherty & Codding 3,821,949 July 2, 1974 An improved bio-feedback apparatus for sensing the brain-wave potentials produced by a subject wherein the sensed brain-wave potentials are processed through separate parallel processing channels of a controlling channel, each processing channel processing a preselected frequency range of the sensed brainwave potential to provide subject-preceivable feedback signals indicative of signal presence within the preselected frequency of each processing channel. Each processing channel is constructed to provide predetennined signal amplitude and duration criteria for determining signal presence prior to initiating and terminating the feedback signals and, in one form, each processing channel is constructed to provide feedback signals indicative of the percentage of time during a subsequent predetermined epoch of time wherein a signal presence existed in the sensed brainwave potential. In one form, the bio-feedback apparatus simultaneously produces audible feedback signals, each audible feedback signal having a separately identifiable tone indicative of signal presence within the preselected frequency range of the processing channels.

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Me I?! 152 VGLUME' ON-OFF ALFHA cat/real. mvreat oar/Ame aw #44 we BIO-FEEDBACK APPARATUS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates in general to improvements in bio-feedback apparatus and, more particularly, but not by way of limitation, to a bio-feedback apparatus for providing subject-perceivable feedback signals indicative of a controlled signal presence within preselected frequency ranges of a sensed brain-wave potential via separate parallel processing channels.

2. Description of the Prior Art In the past there. have been various devices constructed to sense brain-wave potentials, such devices being commonly referred to as electroencephalographic equipment, and the sensed brain-wave potentials being commonly referred to simply as EEG signals. In the simplest form, the brain-wave potentials are detected and the sensed potentials are plotted on a graph-type, read-out. Other devices have been constructed to sense the brain-wave potentials, and to utilize the sensed potentials or portions thereof for providing certain feedback indications.

voluntary device disclosed in the past was described in the US. Pat. No. 3,548,812, issued to Paine. This patent disclosed an electroencephalographic apparatus for quantitatively measuring brain activity and utilizing the measured brain-wave activity for indicating a level of consciousness. The sensed brain-wave activity was amplified and passed through a bandpass filter having a passband generally between 0.7 Hz and 13.0 Hz, the filtered signal being subsequently fed through the three adjustable amplitude comparators having adjustable gain controls. Each of the amplitude comparators produced an output signal when the input signal was within the threshold setting of the amplitude comparator, the three output signals being utilized to generate signals indicative of various stages of sleep or consciousness and subsequently being fed through an analog adder.

The US. Pat. No. 3,032,029, issued to Cunningham, disclosed an apparatus for indicating the alertness of an individual and providing a means for stimulating the individual in response to a preset alertness level. The Cunningham apparatus utilized the alpha and the theta EEG signals which were passed through separate bandpass filters, threshold amplifiers, and diode rectifiers to the input of a coincidence circuit constructed to produce an output signal when the alpha and the theta signals were simultaneously applied thereto. The output of the coincidence circuit activated a remote warning and a random sequencer for enabling and disenabling a plurality of gates for activating various other warning devices such as a light stimulator, a sound stimulator and an electrical stimulator.

The US. Pat. No. 3,195,533, issued to Fischer, disclosed an apparatus for detecting physiological conditions wherein sensed electrical signals from spaced locations on an individual s body were fed through a filter for passing only certain frequency components and subsequently passed through a control circuit for providing an output signal having an average voltage responsive to the frequency of the sensed electrical signals. The control circuit of the Fischer apparatus generaliy included: a limiter means for controlling peak amplitude; a discriminator for providing a pulse for each reversal in polarity of the limiter output signal;

and an integrator providing an output signal having an amplitude proportional to the average DC component of the pulses from the discriminator, the integrator output signal being utilized to control the output signal from the Fischer apparatus.

Various other devices for recording and analyzing EEG responses or the like are typlified in the US. Pat: No. 2,860,627, issued to Harden; No. 2,848,992, issued to Pigeon; and No. 3,513,834, issued to Suzuki, for example.

SUMMARY OF THE INVENTION An object of the invention is to provide a biofeedback apparatus having an improved, more efficient and more accurate .apparatus for developing feedback signals indicative of signal presence within preselected frequency ranges of a sensed brain-wave potential.

Another object of the invention is to provide an improved bio-feedback apparatus for simultaneously providing subject-perceivable and distinguishable audible feedback signals indicative of signal presence within preselected frequency ranges.

One other object of the invention is to provide a biofeedback apparatus for simultaneously processing brain-wave potentials of a controlling channel through parallel processing channels for developing feedback signals indicative of signal presence in the processing channels.

Yet another object of the invention is to provide an improved bio-feedback apparatus for providing feedback signals indicative of the percentage of time during a predetermined epoch period of time wherein signal presence existed in the sensed brain-wave potential.

An additional object of the invention is to provide a bio-feedback apparatus having an improved apparatus for assuring signal presence within predetermined criteria prior to initiating feedback signals.

Another object of the invention is to provide a biofeedback apparatus having an improved apparatus for assuring an absence of signal presence for a predetermined period of time prior to terminating feedback signals.

One additional object of the invention is to provide an improved bio-feedback apparatus for selectively providing feedback signals indicative of signal presence within controlled combinations of frequency ranges.

Another object of the invention is to provide an improved apparatus for selectively passing a signal component of a predetermined frequency range through separate processing channels.

A further object of the invention is to provide an improved bio-feedback apparatus which is more efficient and more economical in the construction and operation thereof.

Other objects and advantages of the invention will be evident from the following detailed description when read in conjunction with the accompanying drawings which illustrate various embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatical view of a bio-feedback apparatus for producing feedback signals constructed in accordance with the present invention.

FIG. 2 is a diagrammatical view of another biofeedback apparatus constructed to produce feedback signals, similar to the bio-feedback apparatus of FIG. 1.

FIG. 3 is a schematic, diagrammatical drawing showing the amplifier assembly and the sensitivity adjustment assembly of the bio-feedback apparatus of FIG. 2.

FIG. 4 is a schematic view showing a typical oscillator, one such oscillator being utilized in each of the processing channels of the bio-feedback apparatus of FIG. 2.

FIG. 5 is a schematic view of a typical control voltage generator, one such voltage control generator being utilized in each of the processing channels of the biofeedback apparatus of FIG. 2.

FIG. 6 is a schematic view of the summing amplifier and the output indicator of the bio-feedback apparatus of FIG. 2.

FIG. 7 is a typical filter construction, one such filter being utilized in each of the processing channels of the bio-feedback apparatus of FIG. 2.

FIG. 8 is a diagrammatical view showing a filter response curve for a filter utilized in one of the processing channels constructed in accordance with the filter construction of FIG. 7.

FIG. 9 is a diagrammatical view showing a filter response curve for another filter utilized in one of the processing channels constructed in accordance with the filter construction of FIG. 7.

FIG. 10 is a diagrammatical view, similar to FIGS. 1 and 2, but showing yet another bio-feedback apparatus constructed to produce feedback signals.

FIG. 11 is a diagrammatical view of a portion of the feedback signal controller of the bio-feedback apparatus of FIG. 10. I

FIG. 12 is a diagrammatical view of a portion of the data reduction controller of the bio-feedback apparatus of FIGS. 10 and 11.

FIG. 13 is a schematic, diagrammatical view of one signal input controller of the bio-feedback apparatus of FIGS. l0, l1 and 12.

FIG. 14 is a schematic view of a portion of the feedback signal controller of the bio-feedback apparatus of FIGS. l0, l1 and 12. i a

FIG. 15 is a schematic view of one zero crossing detector of the bio-feedback apparatus of FIGS. 10,11 and 12.

FIG. 16 is a schematic view of one amplitude discriminator, one comparator controller, and one automatic gain control of the bio-feedback apparatus of FIGS. 10, I1 and 12.

FIG. 17 is a schematic view of one tachometer network of the bio-feedback apparatus of FIGS. 10, 11 and 12.

FIG. 18 is a schematic view of one function generator constructed for a predetermined frequency range for utilization with one tachometer network, constructed as typically shown in FIG. 17, in the bio-feedback apparatus of FIGS. 10, l1 and 12.

FIG. 19 is a schematic view, similar to FIG. 18, but showing one other function generator constructed for a predetermined frequency range for utilization with .one tachometer network, constructed as typically shown in FIG. 17, in the bio-feedback apparatus of FIGS. 10, l1 and 12.

FIG. 20 is a schematic view of one voltage controlled oscillator, one signal converter, and a position of one interconnecting network between a signal converter and an automatic gain control of the bio-feedback apparatus of FIGS. 10, 11 and 12.

FIG. 21 is a schematic view of one bandpass controller of the bio-feedback apparatus of FIGS. l0, l1 and 12.

FIG. 22 is a schematic view of a portion of one audio output controller of the bio-feedback apparatus of FIGS. 10, 11 and 12.

FIG. 23 is a schematic view of a portion of one audio output controller and a portion of one audio output indicator of the bio-feedback apparatus of FIGS. 10, 11 and 12.

FIG. 24 is a schematic view of one analog switch of the bio-feedback apparatus of FIGS. 10, 11 and 12.

FIG. 25 is a diagrammatical, schematic view of one overvoltage controller of the bio-feedback apparatus of FIGS. 10, 11 and 12.

FIG. 26 is a diagrammatical, schematic view of one portion of a counter controller of the bio-feedback apparatus of FIGS. 10, 11 and 12.

FIG. 27 is a schematic view of one digital/analog converter of the bio-feedback apparatus of FIGS. 10, l1 and 12.

FIG. 28 is a diagrammatical, schematic view of one portion of a counter controller of the bio-feedback apparatus of FIGS. 10, 11 and 12.

FIG. 29 is-a diagrammatical, schematic view of one portion of one visual output controller and one associated visual output indicator of the bio-feedback apparatus of FIGS. 10, 11 and 12.

FIG. 29, is 'a diagrammatical, schematic view, similar to FIG. 29, but showing one other portion of one visual output controller and one associated visual output indicator of the bio-feedback apparatus of FIGS. l9, l1 and 12.

FIG. 31 is a schematic view of aportion of one visual output controller of the bio-feedback apparatus of FIGS. 10, 11 and 12.

DESCRIPTION OF THE- PREFERRED EMBODIMENTS reference numeral 10, is a bio-feedback apparatus for sensing and detecting physiological and psychophysiological states and changes of a particular subject and providing subject-perceivable feedback indications of the sensed physiological and psychophysiological variables which is particularly useful in phychophysiological research and training. More particularly, the biofeedback apparatus 10 is useful in inducing, promoting, sensing and detecting certain physiological and psychophysiological variables related to and indicative of various internal states and conditions such as, for example, attention, consciousness, thought," creativity and levels of various emotions, and for teaching and enhancing voluntrary control of these various internal states and conditions in a manner which will be made more apparent below.

In general, the bio-feedback apparatus 10 includes: a sensing assembly 12 detecting and sensing various physiological and psychophysiological states and conditions of a subject and providing an output electrical signal 14 responsive thereto; a frequency discriminator 16 receiving the output signal 14 and providing a plurality of output signals 18, each frequency discriminator output signal 18 being indicative of the presence of a signal within a preselected, discrete frequency band in the sensing assembly output signal 14; a feedback signal controller 20 for receiving and processing the received frequency discriminator output signals 18, each output signal 18 being processed in parallel through separate, distinct processing channels of the frequency discriminator 16 and the feedback signal controller 20 for selectively providing predetermined,

selected output signals

22 and 24 from the feedback signal controller 20; a subject feedback controller 26 receiving the feedback signal controller output signal 22 and providing a subject-perceivable output indication indicative of signal presence of the predetermined, preselected, sensed physiological and psychophysiological states and conditions; and a permanent feedback indicator 28 receiving the feedback signal controller output signal 24 and providing a permanent-type of output indication indicative of signal presence of the predetermined, preselected, sensed physiological and psychophysiological states and conditions. The bio-feedback apparatus is constructed to provide a fast, convenient, efficient, positive, and selectively controlled apparatus providing various predetermined, controlled, immediate, subject-perceivable and permanent feedback indications of sensed physiological and psychophysiological states and conditions for subject training and conditioning in the general area of volitional control of various internal states and conditions and for evaluation and analysis to define more finite correlations between the various sensed physiological and psychophysiological states and conditions of one particular subject or particular groups of subjects.

The activity of various areas of an individuals brain has been associated with identifiable and definable conscious and unconscious states and conditions, and it has been determined that subjects can be trained to varying degrees to control both active and passive volitional aspects of the subjects nervous system, for example. It should also be noted that various physiological and psychophysiological internal states and conditions have been correlated and identified with particular frequency components of the sensed potentials produced by as individuals brain. For example, the four major frequency bands are generally referred to as: the Delta" band having an approximate frequency band generally from 0.5 Hz. to 4.0 Hz.; the Theta band having an approximate frequency band generally from 4.0 Hz. to 8.0 Hz.; the Alpha" band having an approximate frequency band generally from 8.0 Hz. to 13.0 Hz.; and the Beta" band having an approximate frequency band generally from l3.0 Hz. to 26.0 Hz. Each of these frequency bands has been identified and associated with a particular physiological or psychophysiological state or condition and, in some instances, it has been determined that the presence of two or more of the frequency bands is also indicative of a predetermined or identifiable physiological or psychophysiological state. or condition.

in the past, devices have been developed for measuring and recording the rhythmetically varying potential produced by an individuals brain, the potential being sensed or detected by electrodes applied to preselected portions of the individuals scalp and the devices were generally constructed to receive the sensed potential and provide a chart-type of output indicative thereof. Apparatus of the type referred to above is generally known as an electroencephalograph, and the brainwave signals which were sensed and recorded by the electroencephalograph are commonly referred to by the letter designations EEG.

In a preferred form, the bio-feedback apparatus 10, shown in FIG. 1, is constructed to sense the varying potential produced by the activity of an individuals brain, and to provide the various feedback indications indicative of or in response to the presence of predetermined portionsof the sensed varying potential. The sensing apparatus 12, more particularly, includes a brain-wave indicator 30 having a portion connected to sense and detect the varying potentials produced by the individuals brain and provide an output signal 32 responsive thereto and indicative thereof; and a brain-wave signal generator 34 receiving the brain-wave indicator output signal 32 and providing the amplified output signal 14 responsive thereto indicative of the sensed brain-wave potential, as mentioned before. In one form, the brainwave indicator 30 includes a number of electrodes which are attached to the individuals scalp, the electrodes being constructed, attached and positioned to sense the brainwave potential produced by the subject and provide the output signal'32. Since the sensed potentials produced by an individual s brain are of a small amplitude, the brain-wave signal generator, more particularly, receives the electrodes output signal 32 and provides an amplified output signal 14.

In one form, the brain-wave indicator 30 is attached to the subject to sense brain-wave potentials from two or more preselected portions of the individuals scalp, thereby providing two or more distinct brain-wave potentials to the input of the brain-wave signal generator 34. In this form, the brain-wave signal generator 34 is constructed such that one of the sensed brain-wave potentials is selectively provided at the brain-wave signal generator output signal 14; the distinct, sensed brainwave potentials each being referred to below as channels and the brain-wave potential selected via the brain-wave signal generator 34 for controlling the feedback indications being referred to-below as the controlling channel.

The controlling channel signal 14 is connected to the frequency discriminator 16, the frequency discriminator l6 selectively detecting predetermined frequency components of the controlling channel signal 14 for processing through separate, parallel processing channels" of the bio-feedback apparatus 10. Thus, each processing channel of the bio-feedback apparatus 10 processes one frequency component, defined by the predetermined passbands of the frequency discriminator l6, and each processing channel is processed via the feedback signal controller 20 to develop and generate the feedback signals 22 and 24. The processing of the preselected frequency components of the detected, received brain-wave potential via parallel processing channels of the feedback signal controller 20 allows the various components and assemblies of the biofeedback apparatus 10 to be sized and constructed for processing a single preselected signal having a predetermined frequency band, thereby facilitating the construction and design of a more efficient, more accurate signal processing assembly for indicating signal presence of a particular frequency component in the detected brain-wave potential. The utilization of separate signal processing channels for the various predetermined, preselected frequency components also provides a bio-feedback apparatus 10 which has a substantially higher stability and, in general, a more selective type circuitry for providing preselected, controlled feedback signals, yet eliminating undesirable artifacts such as those commonly referred to in the art as EEG spike discharges, eye blinks, muscle artifacts, twitches, and the like, for example.

In one preferred embodiment, brain-wave potentials are detected and sensed at two, preselected scalp sites, and the two sensed, brain-wave potentials are processed in parallel through the bio-feedback apparatus via separate channels, each channel including a plurality of parallel processing channels. In this embodiment, the two channels are each utilized to provide subjectperceivable audio feedback in a monaural' or stereo form, and one channel is utilized for control of the artifacts generated in the sensed brain-wave potentials and for control of subject-perceivable feedback presented in a visual and permanent form, as will be made more apparent below.

Electrodes are attached to the subject for detecting and sensing the brain-wave potentials and, initially, two scalp sites on the individuals head are selected-(preferably on opposite sides of the subjects head and generally in the occipital areas) and the electrodes are attached at these preselected scalp sites. In general, the preselected scalp sites are cleaned with an alcohol, electrode paste which is rubbed into the skin to remove the horny layer and permeate the dermal surface with a conductive medium, the electrode paste being utilized to generally assure a low electrode resistance for facilitating the production of a lownoise signal for subsequent processing by the bio-feedback apparatus 10. The electrodes can be applied to the preselected scalp sites by using a Bentonite clay mixture or the like covered by a plastic film, the plastic film being utilized to prevent or substantially reduce the drying tendency of the clay mixture. ln one form, the subjects left ear lobe and right ear lobe are then tied together for use as a reference for monopolar recording of the brain-wave potential. Finally, the electrode attachment is made by rubbing in a salt paste or the like and attaching an ear clip electrode (generally filled with salt paste) to the ear. The ground or neutral is attained via a plate electrode attached to a portion of the subject s wrist, for example. The use of electrodes and the attachment of the electrodes to various portions of the subject to detect brain-wave potentials, as generally described before, is well known in the art. It should be noted, however, that the electrodes may be attached to particular-portions of the individuals scalp to obtain a particular brainwave potential for processing by the bio-feedback apparatus 10.

Description of FIGS. 2 Through 9 Shown in FIGS. 2 through 9 is a bio-feedback apparatus 10a having: a brain-wave indicator 30a producing an output signal 32a indicative of the individuals brainwave potential; a brain-wave signal generator 34a; a frequency discriminator 16a; and a feedback signal controller a. As diagrammatically shown in FIG. 2, the brain-wave indicator a generally includes: a reference electrode 38 providing an output signal 40; a neutral electrode 42 providing an output signal 44; and an active electrode 46 providing an output signal 48. The reference electrode 38, the neutral electrode 42, and the active electrode 46 are, in a preferred form, each attached to preselected scalp sites of the subject for detecting and sensing brain-wave potentials, in a manner as generally described before. More particularly and for example, the reference electrode 38 can be attached to the subjects left ear lobe, the neutral electrode 42 can be attached to the subjects right ear lobe, and the active electrode 46 can be attached to a predetermined scalp site on the individuals head such as the left occipital area or the right occipital area of the individuals head, it being understood that the particular electrodes utilized and the particular attachment sites of the electrodes on the subject are determined in each application such that the

electrodes

38, 42 and 46 detect and sense particular, preselected brain-wave potentials.

The output signals 40, 44 and 48 of the

electrodes

38, 42 and 46 are each connected to and received by a portion of the brain-wave signal generator 34a. As shown in FIG. 2, the brain-wave signal generator 34a, more particularly, includes: a receiver control 50 connected to the electrodes 38,- 42 and 46 to receive the output signals 40, 44 and 48, respectively, therefrom and to provide an output signal 52 in response to the received signals 40, 44 and 48; a preamplifier 54 which is connected to the receiver control 50 receiving the receiver control output signal52 and providing an amplified output signal 56 in response thereto; an amplifier assembly 58, having a plurality of amplifiers, each amplifier receiving the amplified output signal 56 and providing an amplified output signal in response to the received preamplifier output signal 56; and a sensitivity adjustment assembly 60 having a portion connected to each amplifier of the amplifier assembly 58 for adjusting the threshold level of each amplifier. The frequency discriminator 16a includes a filter assembly 62 having a filter receiving the amplified output signal from the amplifier assembly 58, each filter selecting and passing signals within a predetermined frequency range. The feedback signal controller 20a includes: a control voltage generator assembly 64 having one portion connected to one of the filters of the filter assembly 62, each portion receiving the filter output signal from one of the filters of the filter assembly 62 and developing a feedback control voltage indicating predetermined signal presence within the frequency band of the filter connected thereto; an oscillator assembly 66 having one portion connected to a portion of the control voltage generator assembly 64 for receiving the feedback control voltages developed via the control voltage generator assembly 64, the oscillator assembly 66 providing a plurality of oscillator output signals in response to a predetermined, received feedback control voltage from the control voltage generator assembly 64, each oscillating output signal having an identifiable frequency indicative of a signal presence within a preselected frequency range; a volume control assembly 68 receiving the output signals from the oscillator assembly 66, and selectively and adjustingly controlling the volume of each signal; an on-off control assembly 70 interposed between the oscillator assembly 66 and the volume control assembly 68 for selectively passing predetermined oscillating output signals from the oscillator assembly 66; a summing amplifier 72 receiving the oscillating output signals connected thereto via the onoff control assembly 70 and providing an output signal 74 in response to the received input signals; and an output indicator 76 receiving the summing amplifier output signal 74 and providing a subject-perceivable feed- 9 back indication responsive to the received signal from the summing amplifier 72.

As shown in FIG. 2, the

electrodes

38, 42 and 46 are connected to the subject such that a single brain-wave potential is sensed and detected; the single, sensed brain-wave potential constituting the controlling channel of the bio-feedback apparatus a. The biofeedback apparatus 10a includes three

processing channels

78, 80 and 82, each processing

channel

78, 80 and 82 receiving the preamplifier output signal 56 and developing a feedback signal indicative of a controlled, predetermined signal presence.

The amplifier assembly 58, more particularly, includes an Alpha amplifier 84, a Beta amplifier 86, and a Theta amplifier 88; the Alpha amplifier 84 receiving the preamplifier output signal 56 and providing an amplified output signal 90 in response thereto; the Beta amplifier 86 receiving the preamplifier output signal 56 and providing an amplifier output signal 92 in response thereto; and the Theta amplifier 88 receiving the preamplifier output signal 56 and providing an amplifier output signal 94 in response thereto.

An Alpha sensitivity adjustment 96 is connected to the Alpha amplifier 84 to receive the amplified output controlling the threshold level of the Alpha amplifier 84; a Beta sensitivity adjustment 98 is connected to the Beta amplifier 86 to receive the amplified output signal 92 therefrom and provide an output signal for controlling the threshold level of the Beta amplifier 86; and a Theta sensitivity adjustment 100 is connected to the Theta amplifier 88 to receive the amplified output sig nal 94 therefrom and provide an output signal for controlling the threshold level of the Theta amplifier 88. The Alpha sensitivity adjustment 96, the Beta sensitivity adjustment 98 and the Theta sensitivity adjustment 100 are each part of the sensitivity adjustment assembly 60, each of the

sensitivity adjustments

96, 98 and 100 controlling the threshold level of the

amplifier

84, 86 and 88 connected thereto, during the operation of the bio-feedback apparatus 10a.

The filter assembly 62 includes anAlpha filter 102, a Beta filter 104 and a Theta filter 106. The Alpha filter 102 is connected to the Alpha amplifier 84 to receive the amplified output signal 90, the Alpha filter 102 being constructed, in one form, to have a pass band in the range of approximately 8.3 Hz. to 13.0 Hz. The Beta filter 104 is connected to the Beta amplifier 86 for receiving the amplified output signal 92, and is constructed, in one form, to have a pass band in the range of approximately 14.0 Hz. to 26.0 Hz. The Theta filter 106 is connected to the Theta amplifier 88 to receive the amplified output signal 94, and is constructed to have a pass band in the range of approximately 4.0 Hz. to 7.7 Hz. The Alpha filter 102, the Beta filter 104 and the Theta filter 106 each have an

output signal

108, 110 and 112, respectively, and each

output signal

108, 110 and 112 is a signal having a frequency within the pass band of the filter connected thereto, the filter output signals 108, 110 and 112 thereby indicating the signal presence in the sensed, detected brain-wave potential of a discrete, predetermined frequency band (corresponding to the pass band of the particular filter).

The control voltage generator assembly 64, more particularly, includes an Alpha control voltage generator 114, a Beta control voltage generator 116 and a Theta control voltage generator 118. The Alpha control voltage generator'l14 receives the Alpha'filter output signal 120 in response thereto indicating signal presence of a signal having a frequency generally between 8.3 Hz. and 13.0 Hz. (the pass band of the Alpha filter 102). The Beta control voltage generator 116 receives the Beta filter output signal and produces a feedback control signal 122 in response thereto indicating signal presence of a signal having a frequency generally between 14.0 Hz. and 26.0 Hz. (the pass band of the Beta filter 104). The Theta control voltage generator 118 receives the Theta filter output signal 112 and provides a feedback control signal 124 in response thereto indicating signal presence of a signal having a frequency generally between 4.0 Hz. and 7.7 Hz. (the pass band of the Theta filter 106).

The oscillator assembly 66 includes an Alpha oscillator 126, a Beta oscillator 128 and a Theta oscillator 130. The Alpha oscillator 126 receives the feedback signal from the Alpha control voltage generator 114 and provides an oscillating output signal 132 in response thereto; the Beta oscillator 128 receives the feedback control signal 122 of the Beta control voltage generator 116 and provides an oscillating output signal 134 in response thereto; and the Theta oscillator 130 receives the feedback control signal 124 from the Theta control voltage generator 118 and provides an oscillating output signal l36.in response thereto.

In a preferred form, the Alpha oscillator l26 is constructed to provide an output signal 132 having a frequency of approximately 800 Hz.; the Beta oscillator 128 is constructed to provide an output signal having a frequency of approximately 1100 Hz.; and the Theta oscillator 130 is constructed to provide an output signal having a frequency of approximately 600 Hz. The lastmentioned frequencies of the output signals 132, 134 and 136 of the

oscillators

126, 128 and 130, respectively, were selected, in one operational embodiment, to provide audible, subject-perceivable feedback signals which can be identified when simultaneously presented via the output indicator 76.

The volume control assembly 68 includes volume controls 138, 140 and 142 receiving the oscillating output signals 132, 134 and 136, respectively, each of the volume controls 138, 140 and 142 being constructed to adjust the loudness" of the output signals 132, 134 and 136 connected thereto. The on-off control assembly 70 includes on-off

controls

144, 146 and 148, each being interposed generally between one of the

oscillators

126, 128 and 130 and one of the 'volume controls 138, 140 and 142, connected thereto, as shown in FIG. 2. Each of the on-off

controls

144, 146 and 148 is constructed to connect and disconnect the output signal of the oscillator connected thereto in the on" and the off positions, respectively, of the on-off

controls

144, 146 and 148. In this manner, the feedback indications provided by the bio-feedback apparatus 10a can be selectively controlled such that any one of the

oscillators

126, 128 and 130 or any combination of the

oscillators

126, 128 and 130 can be connected to the summing amplifier 72 and utilized to provide feedback indications for training a subject or for indicating particular physiological and psychophysiological states of the subject.

in summary, the processing channel 78 includes the Alpha amplifier 84, the Alpha sensitivity adjustment 96, the Alpha filter 102, the Alpha control generator 114, the Alpha oscillator 126, the volume control 138 Theta amplifier 88, the Theta sensitivity adjustment 100, the Theta filter 106, the Theta control voltage generator 1 18, the Theta oscillator 130, the on-off control 148 and the volume control 142. The various components and assemblies of the

processing channels

78, 80 and 82 cooperate to develop and provide the feedback signals 132, 134 and 136, respectively, to the summing amplifier 72 indicating the presence of a signal having a frequency within the pass band of the Alpha filter 102, the Beta filter 104, and the Theta'filter 106, respectively.

The output signal 72 of the mixer or the summing amplifier 72 is indicative of and contains the oscillating output signals 132, 134 and 136, in an on position of the respective on-off

controls

144, 146 and 148, the summing amplifier output signal 74 being a mix of the oscillator output signals 132, 134 and 136. The output indicator 76 is constructed to provide subjectperceivabile audible and visual output indications indicative of signal presence at predetermined criteria and having a frequency within the pass band of the

processing channels

78, 80 and 82.

It should be particularly noted that other processing channels, similar to the

processing channels

78, 80 and 82 can be incorporated in the bio-feedback apparatus 19.: to provide a feedback indicative of signal presence of signals having frequencies within frequency band ranges other than the Alpha band, the Beta band, and the Theta band, described before. The additional processing channels can be connected in parallel with the

processing channels

78, 80 and 82, described before, each additional channel generally including the various components and assemblies identified with and connected in the

processing channels

78, 80 and 82, described above.

Referring more particularly to the receiver control 50,.as shown in FIG. 2, the receiver control 50, in a preferred form, can include a switching network interposed between the electrode output signals 40, 44 and 48 and the preamplifier 52 for selectively connecting the reference electrode 38, the neutral electrode 42 and the active electrode 46 into various portions of an electrode resistance check network wherein the resistance between the reference electrode 38 and the neutral electrode 42 can be measured, in one switch position, and the electrode resistance generally between the reference electrode 38 and the active electrode 46 can be measured, in one other switch position, for example. In this form, a battery type supply voltage, for example, can be connected across the electrodes and a resistance type network can be interposed between the electrodes being tested and a meter such that the meter provides an-output indication of the electrode. resistance, thereby assuring that the electrical resistances of the

electrodes

38, 42 and 46 are within operable tolerance limits before switching the receiver control 50 to an operate position wherein the output signals 40, 44 and 46 of the electrodes are connected to the preamplifier 54.

The bio-feedback apparatus a, as shown in FIG. 2, is particularly constructed to provide a compact, portable feedback type of apparatus and, in this form, the operating supply voltages for the various components and assemblies of the bio-feedback apparatus would be supplied via a battery type of power supply. In this form, the receiver control 50 can also be constructed to include a switch position for connecting the batteries to a meter type indicator for checking the operating condition of the batteries, and a built-in battery recharger unit can also be incorporated with the biofeedback apparatus 10a.

The preamplifier 54 is, in a preferred form, a differential, fixed gain type of preamplifier having a low noise level and constructed to receive low amplitude signals from the

electrodes

38, 42 and 46. Preamplifiers of this type are commercially available, and the construction and operation of such preamplifiers is well known in the art.

As shown in FIG. 3, and, as generally described before, the preamplifier output signal 56 is applied to the input of three amplifiers or, more particularly, to the input of the Alpha amplifier 84, the input of the Beta amplifier 86, and the input of the Theta amplifier 88, the

amplifiers

84, 86 and 88 each being connected in parallel for receiving the preamplifier output signal 56. The ground connection is provided via a resistor 150, as shown in FIG. 3.

In one form, the Alpha amplifier 84, the Beta amplifier 86 and the Theta amplifier 88 are each of the integrated circuit type of construction and a positive power supply (not shown) is connected to each

amplifier

84, 86 and 88 via the pin connections 152 and a negative power supply (not shown) is connected to each

amplifier

84, 86 and 88 via the pin connections 154. In this form, a resistor 156 connected in series with a capacitor 158, the resistor 156 and the capacitor 158 being connected to the internal components of each

amplifier

84, 86 and 88, and a resistor 160 connected in series with a capacitor 162 and in parallel with a capacitor 164 is also connected to the internal components of each

ampoifier

84, 86 and 88 for frequency compensation of the

amplifiers

84, 86 and 88, the capacitor 164 being also conected to the respective amplifier output signal, as shown in FIG. 3. Each

amplifier

84, 86 and 88 also includes a feedback loop 165 between the amplifier output signal and the negative input differential signal to each of the

amplifiers

84, 86 and 88, and a pair of

diodes

166 and 168 are interposed in each feedback loop. The negative differential input to the

amplifiers

84, 86 and 88 is connected to ground via a resistor 170 interposed in each ground connection.

An additional feedback loop 172 is connected between the input signal 56 and the output signal of each

amplifier

84, 86 and 88, and a resistor 174 and a variable resistor 176 are interposed in each feedback loop 172. As shown in FIG. 3, the feedback loop 174 is parallel to and generally included within the feedback loop 165. Each of the

amplifiers

84, 86 and 88 is generally a differential type of amplifier having two input circuits, one input circuit being the preamplifier output signal 56 and the other input circuit being controlled via the

feedback loops

156 and 172 and, more particularly, being controlled via the variable resistor 176 interposed in the feedback loop 172 therein. The feedback loops 172 and the variable resistor 176 interposed therein constitute the

sensitivity adjustments

96, 98 and 100 connected to the

amplifiers

84, 86 and 88. Each

amplifier

84, 86 and 88 thus responds to the difference between the two input circuits connected thereto, and the

sensitivity adjustments

96, 98 and 100 essentially constitute the gain control for

amplifiers

84, 86 and 88, the gain controls or

sensitivity adjustments

96, 98 and 100 being, in a preferred form, calibrated in peak-to-peak microvolts and used as threshold sensitivity adjustments for the frequency bands processed through the

various processing channels

78, 80 and 82.

Thus, by selectively adjusting the variable resistors 176 of the sensitivity adjustment assembly 60, the

differential amplifiers

84, 86 and 88 are each adjusted to receive and amplify an input signal controlled by the threshold level setting of the sensitivity adjustment assembly 60 and to reject the preamplifier output signals 56 which do not exceed the minimum threshold level setting of the sensitivity adjustment assembly 60, thereby assuring amplified output signals 90, 92 and 94 from the

amplifiers

84, 86 and 88 of a minimum amplitude and assuring that the biofeedback apparatus will provide feedback signals only when receiving input signals thereto of a minimum amplitude.

The amplifier output signals 90, 92 and 94 are fed through the Alpha filter 102, the Beta filter 104 and the Theta filter 106, respectively, each

filter

102, 104 and 106 selecting and passing only those portions of the input signal having a frequency within the pass band of the particular filter, as described before. Each

filter

102, 104 and 106 is, more particularly, an active, bandpass type of filter having an elliptical response. A filter construction, typical of the construction of the Alpha filter 102, the Beta filter 104 and the Theta filter 106, is shown in FIG. 7, and the filter basically comprises three cascaded, infinite-gain universal type active filter sections (referred to in FIG. 7 as a first'active filter stage 180, a second active filter stage 182, and a third active filter stage 184). The

input signal

90 or 92 or 94 to the

filters

102, 104 and 106, respectively, is connected to the first filter stage 180 via a first feedback network comprising the

resistors

186, 188 and 190 and a capacitor 192. The feedback network connected to the first filter stage 180 is constructed to produce a frequency function (jw) axis of zero, forming an elliptic function characteristic outside the pass band at the lower frequency (f,,) of the filter pass band. The first filter stage 180, in a preferred form, has a relatively low "Q" bandpass function with its resonant frequency (f,,) at the resonant frequency of the

filter

102, 104 or 106 (0" being a quality factor which generally indicates the sharpness of frequency sensitivity of the filter).

The output of the first filter stage 180 is connected to the second filter stage 182 via a conductor 194 through a second feedback network comprising the

resistors

196, 198 and 200 and the capacitor 202, the second feedback network producing a frequency function (jw) axis for the elliptic function characterisitc outside the filter pass band on the upper frequency (f,,) side of the filter pass band. The second filter stage 182 is, in a preferred form, constructed to have a relatively medium Q bandpass function having its (the second filter stage 182) resonant frequency (1",) just below the upper frequency (f,,) response of the

filters

102, 104 and 106.

The output of the second filter stage 182 is coupled to the third filter stage 184 via conductor 204, the output of the third filter stage 184 being the filter output signals 108 or 110 or 112 of the

filters

102, 104 or 106,

respectively. The third filter stage 184 is, in a preferred form, an adjustable gain, relatively medium Q bandpass function, with its (the third filter stage 184) resonant frequency located jsut above the lower frequency (f response of the

filters

102, 104, 106. It should also be noted that, in one other form, the positioning of the second filter stage 182 and the third filter stage 184 can be reversed with respect to the diagrammatical, schematic showing of the typical filter construction in FIG. 7, without substantially effecting the total filter response.

The filter construction, as shown in FIG. 7 and described above, is constructed to provide a filter having a relatively low pass band ripple and a substantially high or sharp rolloff rate outside the pass band, thereby providing a selective filter response to obtain a sharp channel separation between the frequency bands selected and passed by the Alpha filter 102, the Beta filter 104 and the Theta filter 106 for processing through the

parallel processing channels

78, and 82, respectively, of the bio-feedback apparatus 10b.

In one operational application, for example, an Alpha filter 102, constructed in a manner as described in connection with the typical filter construction shown in FIG. 7, and designed to pass signalshaving frequencies from approximately 8.0 Hz. to 13.0 Hz. has been tested to have a filter response curve substantially as shown in FIG. 8, and a Theta filter 106, constructed in accordance with the typical filter construction shown and described with respect to FIG. 7, has been tested to have a filter response curve substantially as shown in FIG. 9, wherein the Theta filter was designed to pass signals having a frequency from approximately 4.0 Hz. to 7.0 Hz. In this operational example, the voltage input to the Alpha filter and the Theta filter was approximately 0.5 volts (peak-to-peak) and the output voltage of the Theta filter and the Alpha filter was approximately 2.0 volts (peak-to-peak).

The Alpha filter 102 response curve, shown in FIG. 8, indicates a flat-band response from approximately 8.0 Hz. to approximately 12.8 I-Iz., and, from the minus 2.5 db points to the notches of the Alpha filter 102, the Alpha filter 102 had a rolloff rate of approximately 30.0 db per one-half cycle, the pass band having approximately a 0.8 db maximum ripple within the pass band.

The Theta filter 106 response curve, shown in FIG. 9, indicates a flat-band response from approximately 4.2 Hz. to 7.9 Hz., the Theta filter 106 having an equally sharp roll-off rate at the minus 2.5 db points and an equally minimum ripple within the pass band, as shown by the Theta filter response curve.

It should also be noted that the bio-feedback apparatus 10a is constructed such that, when signals are being processed within the Theta band (approximately 4.0 Hz. to 8.0 Hz.) have a frequency of approximately 8.0 Hz., the Theta filter response is down to approximately 2.5 db; but, at a frequency of 9.0 Hz., the Theta filter response is down to approximately 30 db, thereby providing a minimum overlap between the frequency bands being processed via the various processing channels of the bio-feedback apparatus 10a. When the db level is down to approximately 10.0 db, the feedback in that particular processing channel is substantially lost or, in other words, the signal is not of a sufficient strength to indicate a signal presence in that particular processing channel. It should be noted, however, that ther will be feedback in the other processing channels, assuming a signal presence within the frequency range or band width of the particular processing channel. Thus, the

filters

102, 104 and 106 are each constructed and designed to select and finally separate the amplified incoming signals into distinct, separate processing channels with a minimum processing channel signal overlap, the signal overlap being approximately 1.0 cycle wide, in the operational example described above.

A typical control voltage generator which can be utilized as the Alpha, the Beta or the Theta

control voltage generators

114, 116 or 118 (shown in FIG. 2) is shown in FIG. 5, and includes: a phase splitter network 208; a rectifier network 210; and a timing network 212, the operating power supply (not shown) being provided to the

control voltage generators

114, 116 and 118 via a pin connection 214.

The phase splitter network 208 generally consists of a pair of

resistors

216 and 218 connected to the junction 220 and a transistor amplifier 222, the base of the transistor amplifier 222 being connected to the junction 220. The phase splitter network 208 is generally constructed for receiving an

input signal

108, 110 or 112, respectively, from the Alpha filter 102, the Beta 7 filter 104 or the Theta filter 106, respectively, and providing two output signals or waves having different phases or differing in phase relationship. Each

input signal

108, 110 or 112 is coupled in one phase splitter network 208 via a capacitor 224, and one of the phase splitter network output signals is coupled to the rectifie! network 210 via a capacitor 226, the other phase splitter network output signal being coupled to the rectifier network 210 via a capacitor 228. The phase splitter network 208 also includes a resistor 230 connected generally between the collector of the transistor amplifier 222 and the operating power supply (not shown) connected to the pin connection 214 and a resistor 235 connected generally between the emitter of the transistor amplifier 222 and ground.

The rectifier network 210 consists of four diodes connected to form a full-wave diode bridge type of rectifier network, one junction of the diode bridge receiving one of the phase splitter network output signals via the capacitor 226 and one other junction of the diode bridge receiving the other phase splitter network output signal via the capacitor 228. The input signals to the diode bridge are connected to two of the diode bridge junctions, one of the diode bridge junctions, not connected to receive a phase splitter network output signal, is connected to ground, the other diode bridge junction, not connected to receive a phase splitter network output signal, is connected to an output pin connection providing the output signals 120, 122 or 124 of the control voltage generator assembly 64, as indicated in FIGS. 2 and 5.

The timing network 212 includes a cpacitor 236 connected in parallel with a resistor 238, the timing network 212 being interposed generally between the rectifier network 210 and the output signal pin connection of the control voltage generator. The

feedback control signal

120 or 122 or 124 of the

control voltage generators

114 or 116 or 118, respectively, are thus processed through the phase splitter network 208 and through the full-wave diode bridge rectifier network 210 and finally through the timing network 212, the

feedback control

120, 122 and 124 being produced via the

control voltage generators

114, 116 and 118, after a predeter mined time delay controlled by the time constant determined by the values of the'capacitor 236 and the resistor 238 of the timing network 212. The capacitor 236 and the resistor 238 of the timing network 212 are each sized to provide a charge and discharge time constant such that a predetermined number of cycles of the filter output signals 108, 110 and 112 are requried subsequent to the

feedback control voltages

120, 122 and 124, respectively, being produced at the output of the respective

control voltage generators

114, 116 and 118, therebyassuring a signal presence .within one of the

processing channels

78, 80 and 82 for a predetermined, rninimum period of time subsequent to a feedback signal being produced by the bio-feedback apparatus 10a. in this manner the bio-feedback apparatus 10 substantially eliminates feedback signals being produced via a single, short duration, relatively high amplitide, sensed potential, such as signals which might be produced via muscle artifacts or the like, for example.

Thus, the sensitivity adjustment assembly 60 and the control voltage generator assembly 64 cooperate to de termine and set signal criteria for each of the

processing channels

78, 80 and 82 such that an input signal must have a minimum amplitude and exist for a predetermined, minimum period of time subsequent to the feedback control signals 120, 122 and 124 being initiated or generated within the

particular processing channels

78, 80 and 82. The feedback control signals 120, 122 and 124 are, more particularly, d-c control votlages, and are utilized to activate the oscillator connected thereto. A

typical oscillator

126, 128 or 130 is shown in FIG. 4, and the feedback control signals or 122 or 124 are, more particularly, connected to the base of a switching transistor 240 via a resistor 242. The emitter of the switching transistor 240 is connected to ground and the collector of the switching transistor is connected to an oscillator network 244 via a resistor 246. The switching transistor 240 is constructed to be normally biased in the off" position, and to be biased in the on" position when the

feedback control signal

120 or 122 or 124 is applied thereto, thereby biasing or activating the oscillator network 244 in the *on" position, in a manner to be described in greater detail below.

The oscillator network 244 basically consists of a pair of

transistor amplifiers

248 and 250, the collector of the transistor amplifier 248 being connected to an operating power supply (not shown) via a pin connection 252 and the emitter of the transistor amplifier 248 being connected to the collector of the switching transistor 240 via the resistor 246. The collector of the transistor amplifier 250 is connected to the operating power supply (not shown) via the pin connection 252 and the emitter of the transistor amplifier 250 is connected to ground via a resistor 254. A resistor 256 is interposed between the transistor amplifier 248 an the pin connection 252, and a resistor 258 is interposed between the collector of the transistor 250 and the pin connection 252, as shown in FIG. 4. A variable resistor 260 is interposed between the collector of the transistor amplifier 248, and, more particularly, between the resistor 256 and the pin connection 252, and the base of the transistor amplifier 248 is connected to the collector of the transistor amplifier 250 via a resistor 262, a capacitor 264 being connected between the base of the transistor amplifier 248 and the emitter of the transistor amplifier 250. The collector of the transistor amplifier 248 is also connected to the base of the transistor amplifier 250 via a capacitor 268, and the emitter of the transistor amplifier 248 is also connecced to the base of the transistor amplifier 250 via a variable resistor 270.

The

transistor amplifiers

248 and 250, as shown in FIG. 4, and the interconnecting capacitive-resistive network therebetween form the oscillator network 244, the output signal of the oscillator network 244 having a frequency determined by the sizes of the various componets of the oscillator network 244, as well known in the art. The variable resistor 260 is connected in the oscillator network 244 to variably and selectively control the amplitude of the oscillator output signal, and the variable resistor 270 is connected in the oscillator 244 to variably and selectively control the frequency of the oscillator output signal in an operating mode or activated position of the oscillator network 244, during the operation of the bio-feedback apparatus a. in one preferred operational embodiment, the Alpha oscillator 126 is constructed to generate and provide an output signal having a frequency of 800 Hz.; the Beta oscillator 128 is constructed to generate and provide an output signal having a frequency of 1100 Hz.; and the Theta oscillator 130 is constructed to generate and provide an output signal frequency of 600 Hz., as mentioned before.

The oscillating output signals 132, 134 or 136 are connected to the on-off

controls

144, 146 and 148, respectively, via a capacitor 276 connected on one end thereof to the emitter of the transistor amplifier 250, generally between the connection of the capacitor 264 to the emitter of the transistor amplifier 250 and the resistor 254, the on-off

controls

144, 146 and 148 being schematically shown in FIG. 4 as an on-off type of switch. The on-off

controls

144, 146 and 148 are each connected to one of the volume controls 138, 140 or 142 (the volume controls138, 140 or 142 being schematically shown in FlG. 2 as a variable resistor). It should be noted that, in one other form, the

switches

144, 146 and 148 can be eliminated and a potentiometer type of volume control can be utilized in lieu thereof, the volume of the feedback signals supplied to the summing amplifier 72 being controllable from approximately zero to a maximum level via the variable resistor or potentiometer.

The oscillator network 244 is, more particularly, a fixed frequency, constant amplitude, sinusoidal resistance-capacitance coupled type of oscillator network, and the switching transistor 240, more particularly, is constructed such that the feedback control signals 120, 122 and 124 saturate the switching transistor 240 connected thereto, thereby biasing the switching transistor 240 in the on" position allowing current flow through the switching transistor 240 to ground and activating the oscillator network 244. In the on position of the on-off

controls

144, 146 and 148, the feedback oscillator output signals 132, 134 and 136 are each connected to the input of the summing amplifier 72, as diagrammatically shown in FIG. 2.

The summing amplifier 72 and the output indicator 76 of the bio-feedback apparatus 10a is shown in more detail in FIG. 6. The feedback oscillator output signals 132, 134 and 136 are each connected to one of the inputs of the summing amplifier 72 via resistors 278, one

resistor 278 being interposed between the summing amplifier 72 and each feedback

oscillator output signal

132, 134 and 136, respectively. The other input of the summing amplifier 72 is connected to ground, the summing amplifier 72 thereby providing an amplifier of the type generally referred to as a summing" or mixer" type of amplifier. A feedback loop is provided around the summing amplifier 72, generally between the output of the summing amplifier 72 and the signal input to the summing amplifier 72, and a resistor 280 is interposed in the feedback loop.

The output 'of the summing amplifier 72 is connected to the primary side of atransformer 282 and the secondary side of the transformer 282 is connected to a speaker 284 and a headset 286. A switch 288 is interposed between the transformer 282 and the speaker 284, the switch 288 connecting the speaker 284 to the output of the summing amplifier 72 in the closed position thereof and disconnecting the speaker 284 from the output of the summing amplifier 72 in the open position thereof.

The summing amplifier 72 thus receives the feedback oscillator output signals 132, 134 and 136 and provides an output signal indicative of the signal mix thereof, the summing amplifier output signal being transformer coupled to the speaker 284 and the headset 286 for providing a subject-perceivable auditory type of feedback, each feedback signal indicating the presence of a sensed signal within the preset frequency ranges of one of the

processing channels

78, and 82. As mentioned before, the oscillator output signals 132, 134 and 136 each have a preselected frequency such that the separate tones being simultaneously amplified and produced via the summing amplifier 72 are distinguished by the subject or, in other words, such that when two or more oscillator output signal tones are bieng produced simultaneously by two or more of the

feedback processing channels

78, 80 and 82, the simultaneously produced feedback oscillator output signals 132, 134 and 136 are individually identifiable and distinguishable by the subject. It should also be noted that the output indicator 76 can include other forms of audio feedback, and can also be constructed to produce various forms of visual feedback indications. In any event, the subject-perceivable feedback produced during the operation of the bio-feedback apparatus 10a is indicative of a signal presence in one of the

processing channels

78, 80 and 82 wherein the signal has a minimum preset amplitude and is of a minimum predetennined duration.

Description of FIGS. 10 through 31 Shown in FIGS. 10 through 31 is a bio-feedback apparatus 10b, constructed similar to the bio-feedback apparatus 10 and 10a, described before, to sense and detect brain-waves or varying potentials produced by the subject and to process predetermined, preselected portions of the varying potential through separate processing channels to produce sugject-perceivable feedback indications indicative of various parameters related to the presence of a predetermined, identifiable signal component portion of the detected and sensed brain-wave potential from the subject. The biofeedback apparatus 10b includes a brain-wave indicator 30b, constructed similar to the brain-wave indicator 30a of FIG. 2, the brain-wave indicator 30b including: a reference electrode 310 attached to the subject and

Claims

1. A bio-feedback apparatus for sensing the brain-wave potentials produced by a subject and providing feedback signals in response thereto, the apparatus comprising: a brain-wave indicator detecting and sensing brain-wave potentials, and providing an output signal responsive thereto; a preamplifier receiving the brain-wave indicator output signal and providing an amplified output signal responsive thereto; a plurality of processing channels, each processing channel receiving the preamplifier output signal and providing a feedback signal responsive thereto, each processing channel comprising: a passband filter, having a predetermined passband, receiving the preamplifier output signal and providing an output signal responsive to a frequency component of the received signal within the passband; and means receiving the passband filter output signal and providing an output signal indicative of signal presence in the processing channel, including: an oscillator, interposed in each processing channel, each oscillator in each processing channel receiving the passband filter output signal and generating an output signal having a distinct, separately identifiable frequency in response thereto, the oscillator output signals indicating signal presence in the processing channels; a feedback indicator receiving the output signals indicative of the signal presence from each of the processing channels and providing subject-perceivable feedback signals responsive thereto, the feedback indicator including: a summing amplifier receiving the oscillator output signal from each of the oscillators in each processing channel and providing a single output signal in response to the received oscillator output signals; and an output indicator receiving the summing amplifier output signal and providing a subject-perceivable output indication responsive thereto.

2. The bio-feedback apparatus of claim 1 wherein the means receiving the passband filter means output signal is defined further to include: a full-wave rectifier providing an output signal in response to a received input signal; means connected to the full-wave rectifier receiving the passband filter output signal and providing an input signal to the full-wave rectifier; a timing netwOrk receiving the full-wave rectifier output signal and providing a feedback control voltage in response to a received signal of a predetermined minimum duration thereby substantially eliminating feedback indications produced via relatively short duration sensed brainwave potentials; and switch means having an ''''on'''' and an ''''off'''' condition connected to the timing network and the oscillator, the switch means receiving the feedback control voltage and being biased in the on condition in response thereto activating the oscillator in the ''''on'''' condition, the oscillator providing the output signal indicating signal presence in the processing channels.

3. The bio-feedback apparatus of claim 2 wherein each processing channel is defined further to include: an amplifier receiving the preamplifier output signal and providing an amplified output signal in response thereto; and sensitivity adjustment means connected to the amplifier controlling the threshold sensitivity setting of the amplifier connected thereto, the amplifier providing an amplifier output signal in response to a received preamplifier output signal having an amplitude exceeding the threshold setting of the sensitivity adjustment means connected thereto.

4. A bio-feedback apparatus for sensing the brain-wave potentials produced by a subject and providing the feedback signals in response thereto, the apparatus comprising: a brain-wave indicator sensing the brain-wave potentials, and providing an output signal responsive thereto; a preamplifier receiving the brain-wave indicator output signal and providing an amplified output signal responsive thereto; a plurality of processing channels, each processing channel receiving the preamplifier output signal and providing a feedback signal responsive thereto, each processing channel comprising: a passband filter, having a predetermined passband, receiving the preamplifier output signals and providing an output signal responsive to a frequency component of the received signal within the filter passband; means receiving the passband filter output signal and providing an output signal indicating signal presence in the processing channel, including: comparator means, having an upper and a lower amplitude threshold limit, receiving the passband filter output signal and providing an output signal in response to a received preamplifier output signal, the comparator means output signal being ''''low'''' when receiving a preamplifier output signal having an amplitude level within the upper and the lower amplitude threshold limits of the comparator means; switch drive means receiving the comparator means output signal, having a biased ''''on'''' and a biased ''''off'''' condition, the switch drive means being biased in the ''''on'''' condition when receiving a ''''low'''' comparator means output signal; a threshold adjust means connected to the switch drive means receiving the switch drive means output signal in an ''''on'''' condition of the switch drive means and providing an output signal when receiving a switch drive means output signal of a predetermined minimum duration, the threshold adjust means output signal being terminated via the switch drive means output signal remaining switched to the ''''off'''' position for a predetermined minimum period of time; and switch network means connected to the threshold adjust means having an ''''on'''' and an ''''off'''' condition, the switch network means biased in the ''''on'''' condition when receiving a threshold adjust means output signal indicating signal presence in the particular processing channel; and feedback indicator means receiving the output signals indicative of signal presence from each of the processing channels and providing subject-perceivable feedback signals responsive thereto and indicative thereof.

5. The bio-feedback apparatus of claim 4 wherein the means in each processing channel receivIng the passband filter output signal and providing an output signal indicating signal presence in the processing channel is defined further to include: amplitude discriminator means receiving the passband filter output signal and providing an output signal substantially proportional to the amplitude of the received passband filter output signal; and comparator controller means receiving the amplitude discriminator output signal and providing ''''high'''' output signal in response to a received amplitude discriminator output signal having a predetermined duration indicating signal presence in the processing channel, the comparator controller output signal being connected to the feedback indicator means for providing subject perceivable feedback signals in response to a comparator controller means ''''high'''' output signal.

6. The bio-feedback apparatus of claim 5 wherein the means in each processing channel receiving the passband filter output signal and providing an output signal indicating signal presence in the processing channel is defined further to include: zero crossing detector means receiving the passband filter output signal and providing a ''''high'''' output signal in response to a negative going zero crossing of the passband filter output signal and a ''''low'''' output signal in response to a positive going zero crossing of the passband filter output signal; tachometer network means receiving the zero crossing detector means output signal providing an output signal substantially linearly proportional to the frequency of the received zero crossing detector means output signal; and means receiving the tachometer network output signal and providing an oscillating output signal having a frequency corresponding to a multiple of the frequency of the sensed potential indicated by the tachometer network output signal; and wherein the feedback indicator means receives the oscillating output signal corresponding to a multiple of the frequency of the sensed potential and provides a subject-perceivable feedback signal responsive thereto indicating signal presence in the particular processing channel.

7. The bio-feedback apparatus of claim 6 wherein the means in each processing channel receiving the passband filter output signal and providing an output signal indicating signal presence in the processing channel is defined further to include: automatic gain control means receiving the amplitude discriminator output signal and the oscillating output signal corresponding to a multiple of the frequency of the sensed potential, the automatic gain control means controlling the volume of the received oscillating signal in response to the received amplitude discriminator output signal and providing an output signal corresponding to received oscillating signal having the volume thereof controlled in response to the received amplitude discriminator output signal; feedback indicator means is defined further to include an audio output indicator receiving the automatic gain control output signal and providing audible subject-perceivable feedback signal responsive thereto.

8. The bio-feedback apparatus of claim 7 wherein the means providing an oscillating output signal in response to a received tachometer network output signal is defined further to include: non-inverting amplifier means receiving the tachometer network means output signal and providing an amplified output signal in response thereto; unity-gain inverting amplifier means receiving the non-inverting amplifier output signal and providing an inverted output signal in response thereto; first diode bridge means connected to and receiving the non-inverting amplifier means output signal and the unity-gain inverting amplifier means output signal; amplifier means having an output signal connected to the first diode bridge means; second diode bridge means connected to the amplifier means providing an output signal driving the amplifier means; inTegrator amplifier means connected to the first diode bridge means and providing a triangularly shaped output signal, the integrator amplifier means output signal being connected to the amplifier means controlling the amplitude of the triangularly shaped signal produced by the integrator amplifier means; and signal converter means receiving the integrator amplifier means output signal and providing a sine-wave shaped output signal in response thereto, the signal converter means output signal being connected to automatic gain control means and providing the oscillating signal input connected thereto.

9. The bio-feedback apparatus of claim 6 wherein the means in each processing channel receiving the passband filter output signal and providing the output signal indicating signal presence in the processing channel is defined further to include: bandpass controller means, having a high and a low threshold setting and providing a ''''high'''' and a ''''low'''' output signal, receiving the tachometer network means output signal and providing a ''''low'''' output signal in response to a received tachometer network means output signal within the high and the low threshold setting of the bandpass controller means; and wherein the comparator controller means receives the bandpass controller means output signal, the comparator controller providing a ''''high'''' output signal in response to a received ''''low'''' bandpass controller means output signal indicating signal presence in the processing channel within the high and the low threshold settings of the bandpass controller means output signal.

10. The bio-feedback apparatus of claim 9 wherein the tachometer network means includes: an oscillator means having an ''''on'''' and an ''''off'''' condition, the oscillator means receiving the zero crossing detector means output signal and being biased in the ''''on'''' condition in response thereto providing an oscillator means output signal; and wherein the amplitude discriminator means is defined further to include: discriminator amplifier means receiving the passband filter means output signal and providing an amplified output signal responsive thereto; diode means connected to and receiving the discriminator amplifier means output signal, the diode means being forward biased and conducting when receiving a positive going discriminator amplifier means output signal and being reversed biased and nonconducting when receiving a negative going discriminator amplifier means output signal; capacitor means receiving the discriminator amplifier means output signal and being charged in response thereto in a conducting condition of the diode means; memory capacitor means receiving the charge on the capacitor means when connected thereto; first gate means having an opened and a closed condition connected between the capacitor means and the memory capacitor means, the first gate means receiving the oscillator output signal via the tachometer network means and being biased open in response thereto connecting the capacitor means and the memory capacitor means; switching means connected to the capacitor means having an ''''on'''' and an ''''off'''' condition and receiving the zero crossing detector means output signal, the switching means being biased in the ''''on'''' condition in response to a received zero crossing detector means output signal in the ''''high'''' state discharging the capacitor means connected thereto; and second gate means having an opened and a closed condition connected to the memory capacitor means and to the amplitude discriminator means, the charge on the memory capacitor means biasing the second gate means opened and providing the amplitude discriminator means output signal.

11. The bio-feedback apparatus of claim 10 wherein the tachometer network means is defined further to include: switching means, having an ''''on'''' and an ''''off'''' condition, and receiving the tachOmeter oscillator means output signal and being biased ''''on'''' in response thereto; function generator means connected to the switching means and having a portion charged in the ''''on'''' condition of the switching means, the charged portion being discharged in the ''''off'''' condition of the switching means, the function generator means providing an output signal proportional to the frequency of the sensed brain-wave potential in the discharging condition thereof; memory capacitor means connected to the portion of the function generator charged in the ''''on'''' condition of the switch means and receiving the charge discharged from the function generator means when connected thereto; and switching means connected to the function generator means and to the memory capacitor means, having an ''''on'''' and an ''''off'''' condition, the switching means receiving the oscillator output signal of the tachometer network means and being biased ''''on'''' in response thereto connecting the discharging function generator to the memory capacitor means.

12. The bio-feedback apparatus of claim 11 wherein the function generator means is defined further to include: capacitor means connected to the switching means and being charged in the ''''on'''' condition of the switching means; a resistive network bleed path connected to the capacitor means having a relatively low time constant; a resistive network bleed path connected to the capacitor means having a relatively high time constant; and diode means, having a forward biased and a reverse biased condition, connected to the high time constant resistive network bleed path, the capacitor means discharging through the high time constant resistive network bleed path in a forward biased condition of the diode means and through the low time constant resistive network bleed path in a reverse biased condition of the diode means, the discharging curve of the capacitor means being linearly proportional to the frequency of the sensed brain-wave potential.

13. The bio-feedback apparatus of claim 12 wherein the function generator means is defined further to include: a resistive network bleed path connected to the capacitor means having an intermediate time constant; and diode means connected to the intermediate time constant resistive network bleed path, the capacitor means discharging through the high and the intermediate time constant resistive networks in a forward biased condition of the diode means connected therein, the capacitor means discharging through the intermediate and the low time constant resistive networks in a reverse biased condition of the diode means connected to the high time constant resistive network, and the capacitor means discharging through the low time constant resistive network in a reverse biased condition of the two diode means.

14. The bio-feedback apparatus of claim 9 wherein the comparator controller means is defined further to include: first comparator means, having a predetermined threshold setting, receiving the amplitude discriminator output signal and providing an output signal in a ''''low'''' state in response to a received amplitude discriminator output signal having an amplitude level exceeding the threshold setting of the first comparator means; second comparator means receiving the first comparator means output signal and connected to the capacitor means, having a predetermined threshold setting and providing a comparator controller means output signal in a ''''high'''' state in response to the capacitor means connected thereto being discharged to a potential exceeding the threshold setting of the second comparator means; and capacitor means connected to the second comparator means and to the bandpass controller means discharging in a ''''low'''' state of the first comparator means output signal and in a ''''low'''' state of the bandpass controller means output signal.

15. The bio-feedback apparatuS of claim 14 wherein the bandpass controller means is defined further to include: dual-comparator means, having a predetermined high and a low threshold limit, receiving the tachometer network means output signal and providing a ''''low'''' output signal when receiving a tachometer network means output signal within the high and the low threshold limit; and gate means receiving the dual-comparator means output signal and the first comparator means output signal from the comparator controller means, the gate means being connected to the second comparator means of the comparator controller means and connecting a ''''low'''' output signal to the capacitor means when receiving a ''''low'''' dual-comparator means output signal.

16. The bio-feedback apparatus of claim 9 wherein the bandpass controller means includes: gate means inverting the bandpass controller means output signal and providing a ''''low'''' output signal in response to a received tachometer network means output signal within the high and the low threshold setting of the bandpass controller means; and wherein the feedback indicator means is defined further to include: mixer amplifier means receiving the automatic gain control means output signals connected thereto and providing an amplified output signal responsive thereto; relay means interposed between the mixer amplifier means and the automatic gain control means output signal of each processing channel, the relay means connecting each automatic gain control means output signal to the mixer amplifier means in an energized condition thereof; and drive transistor means connected to the relay means having an ''''on'''' and an ''''off'''' condition and energizing the relay means in the ''''on'''' condition thereof, the drive transistor means receiving each comparator controller means output signal and each output signal of the gate means of each bandpass controller means; diode means connected between the drive transistor means and the comparator controller means output signal and between the drive transistor means and the output signal of the gate means of each bandpass controller means, the drive transistor means being biased ''''on'''' in response to a received ''''high'''' output signal of the gate means of the bandpass controller means and a received ''''high'''' amplitude discriminator means output signal.

17. The bio-feedback apparatus of claim 9 wherein the feedback indicator means is defined further to include: amplifier means having an ''''on'''' and an ''''off'''' condition receiving the comparator controller means output signal and being biased ''''on'''' in response to a comparator controller means output signal in the ''''high'''' state; meter means receiving the tachometer network means output signal, providing a visual feedback signal indicating the frequency of the sensed brain-wave potential; and relay means interposed between the tachometer network means and the meter means, connecting the tachometer network means output signal to the meter means in an energized condition thereof, the relay means connected to the amplifier means and being energized in a biased ''''on'''' condition of the amplifier means.

18. The bio-feedback apparatus of claim 5 wherein the means in each processing channel receiving the passband filter output signal and providing an output signal indicating signal presence in the processing channel is defined further to include: data reduction controller means receiving the comparator controller means output signal indicating signal presence in the processing channel, and having a portion monitoring signal presence in the processing channel over a predetermined epoch period of time. and providing an output signal indicating the percentage of time signal presence existed in the processing channel during a subsequent predetermined period of time, an epoch period of time; and wherein the feedback indicator is defined furTher to include a portion receiving the output signal indicating the percentage of time signal presence existed in the processing channel and providing a feedback indication in response thereto.

19. The bio-feedback apparatus of claim 18 wherein the data reduction means is defined further to include: delay oscillator means generating an output signal; analog switch means receiving the comparator controller means output signal and the delay oscillator means output signal, the analog switch means providing the delay oscillator output signal when receiving a comparator controller means output signal in a ''''high'''' state; delay signal controller means receiving the delay oscillator means output signal via the analog switch means and recording the received delay oscillator means output signal for the predetermined epoch period of time; and means receiving the delay signal controller means output signal and the comparator controller means output signal providing an output signal indicating the average percentage of time signal presence existed in the processing channel for the preceding predetermined epoch period of time in response to the received comparator controller means output signal and the received delay signal controller means output signal; and wherein the feedback indicator means includes a portion receiving the output signals indicating the average percentage of time signal presence existed in each processing channel and provides a subject-perceivable feedback signal response thereto.

20. The bio-feedback apparatus of claim 19 wherein the portion of the feedback indicator means providing the output signal indicative of the average percentage of time signal presence existed in the processing channel is defined further to include: counters for counting up to a predetermined number and counting down to zero, the counters providing a digital output signal indicative of the count registered therein and having a count-up mode, a count-down mode, and a hold mode, the counters positioned in the count-up mode in response to a received count-up signal and positioned in the count-down mode in response to a received count-down signal; overvoltage controller means providing a ''''high'''' and ''''low'''' output signal, and having an upper and a lower threshold limit, the overvoltage controller means receiving the delay signal controller means output signal and providing a ''''high'''' output signal in response to a received delay signal controller means output signal within the upper and the lower threshold limits; and counter controller means connected to the counters and receiving the overvoltage controller means output signal and the comparator controller output signal, the counter controller means providing an output count-up signal in response to a comparator controller means output signal in the ''''high'''' state and an overvoltage controller means output signal in the ''''low'''' stage, and an output count-down signal in response to a received comparator controller means output signal in a ''''low'''' state and an overvoltage controller means output signal in a ''''high'''' state, the digital output signals of the counters providing the output signal indicating the average percentage of time signal presence existed in the processing channel.

21. The bio-feedback apparatus of claim 20 wherein the portion of the feedback indicator means providing the output signal indicative of the average percentage of time signal presence existed in the processing channel is defined further to include: a digital/analog converter receiving the counters output signal and providing an analog voltage output signal responsive thereto indicating the percentage of time signal presence existed in the processing channel.

22. The bio-feedback apparatus of claim 21 wherein the feedback indicator means includes: meter drive network means receiving the digital/analog converter output signal and providing an output signal responsive thereto; and meter means receiving the meter drive network means output signal and providing a visual feedback indicating the average percentage of time signal presence existed in the processing channel connected thereto in response to the received meter drive network output signal.

23. The bio-feedback apparatus of claim 21 defined further to include: clock pulse generator means generating a clock pulse output signal therefrom; and wherein the counters are further defined to provide output signals in the ''''low'''' state in response to a count being registered thereon and to provide output signals in the ''''high'''' state in response to a zero count being registered thereon, the counters being positioned in the count-up mode in response to a received count-up signal and a clock pulse and in the count-down mode in response to a received count-down signal and a clock pulse; and wherein the counter controller means receives the clock pulse output signal and the counters output signal, the counter controller means being defined further to include: gate means receiving the clock pulse output signal, the comparator controller means output signal, the overvoltage controller means output signal and the counters output signals and providing an output count-up signal and a clock pulse in response to a comparator controller means output signal in the ''''high'''' state and an overvoltage controller means output signal in a ''''low'''' state, an output count-down signal and a clock pulse in response to a received comparator controller means output signal in a ''''low'''' state and an overvoltage controller means output signal in a ''''high'''' state, in response to at least one ''''low'''' counters output signal, and providing an output count-up signal and a clock pulse in response to received counters output signal in the ''''high'''' state and a received comparator means output signal in a ''''high'''' state.

24. The bio-feedback apparatus of claim 18 wherein the brain-wave indicator means includes: means detecting and sensing the brain-wave potentials produced at at least two preselected scalp sites, the brain-wave indicator means providing a controlling channel output signal indicating the sensed brain-wave potential at each scalp site; and wherein the preamplifier means receives the controlling channel output signals and provides amplified output signals responsive thereto; and wherein the bio-feedback apparatus includes: an amplitude equalizer, having a portion varying received signals about a preset amplitude reference axis, receiving and varying the amplified controlling channel output signals about the predetermined common amplitude reference axis providing the equalized amplified controlling channel output signals therefrom; and wherein processing channels include a plurality of processing channels receiving each controlling channel output signal and providing a feedback signal responsive to each received controlling channel output signal indicating signal presence in the processing channel.

25. The bio-feedback apparatus of claim 24 wherein the feedback indicator means is defined further to include: first audio means providing subject-perceivable audible feedback signals responsive to a received signal input thereto; second audio means providing subject-perceivable audible feedback signals responsive to a received signal input thereto; and switch means connected to and receiving the feedback signals of each controlling channel output signal, the switch means connected to the first and the second audio means and having one switch position connecting the feedback signal from one controlling channel output signal to the first audio means and the feedback signal from one other controlling channel output signal to the second audio means, and one other switch position connecting the feedback signals from one of the controlling channel output signals to the first and the second audio means.

26. A bio-feedback apparatus for sensing the brain-wave potentials produced by a subject and providing feedback signals in response thereto, the apparatus comprising: a brain-wave indicator detecting and sensing the brain-wave potentials, and providing an output signal responsive thereto; a processing channel receiving the brain-wave indicator output signal and providing a feedback signal responsive thereto, the processing channel comprising: frequency discriminator means having a predetermined passband, receiving the brain-wave indicator output signals and providing an output signal responsive to the frequency component of the received signal within the passband of the frequency discriminator means; means receiving the frequency discriminator means output signal and providing an output signal indicating signal presence in the processing channels; a data reduction controller means receiving the output signal indicating signal presence in the processing channel and providing an output signal indicating the percentage of time signal presence exists in the processing channel for a subsequent predetermined epoch period of time, the data reduction controller means including: delay oscillator means generating an output signal; analog switch means receiving the output signal indicating signal presence in the processing channel and the delay oscillator means output signal, the analog switch means providing the delay oscillator means output signal in response to a received output signal indicating signal presence in the processing channel; delay signal controller means receiving the delay oscillator means output signal from the analog switch means and recording the received delay oscillator means output signal for the predetermined epoch period of time and providing an output signal responsive thereto; and means receiving the delay signal controller means output signal indicating signal presence in the processing channel during the predetermined epoch period of time and providing an output signal indicating the average percentage of time signal presence existed in the processing channel for the predetermined epoch period of time, including: counters for counting up to a predetermined number and counting down to zero, the counters providing a digital output signal indicating the count registered therein and having a count-up mode, a count-down mode, a hold mode, the counters being in the count-up mode when receiving a received count-up signal and being in the count-down mode when receiving a count-down signal; overvoltage controller means providing a ''''high'''' and a ''''low'''' output signal, and having a predetermined upper and a lower threshold limit, the overvoltage controller means receiving the delay signal controller means output signal and providing a ''''low'''' output signal in response to a received delay signal controller means output signal within the upper and the lower threshold limits of the overvoltage controller means; and counter controller means connected to the counters and receiving the overvoltage controller means output signal indicative of signal presence in the processing channel, the counter controller means providing an output count-up signal when receiving an over-voltage controller means output signal in the ''''low'''' state indicating signal presence in the processing channel, and an output count-down signal when receiving an overvoltage controller means output signal in a ''''high'''' state, the count registered in the counters indicating the percentage of time signal presence existed in the processing channel during the predetermined epoch period of time; and feedback indicator means receiving the output signal indicating the percentage of time signal presence existed in the processing channel and providing a subject-perceivable feedback signal responsive thereto.

27. The bio-feedback apparatus of claim 26 wherein the means providing the output signal indicating the average percentage of time signal presence existed in the processing channel is defined further to include: a digital/analog converter receiving the counters output signal and providing an analog voltage output signal responsive thereto indicating the percentage of time signal presence existed in the processing channel.

28. The bio-feedback apparatus of claim 27 defined further to include: clock pulse generator means generating a clock pulse output signal therefrom: and wherein the counters are further defined to provide output signals in the ''''low'''' state in response to a count being registered thereon and to provide output signals in the ''''high'''' state in response to a zero count being registered thereon, the counters being positioned in the count-up mode in response to a received count-up signal and a clock pulse and in the count-down mode in response to a received count-down signal and a clock pulse; and wherein the counter controller means receives the clock pulse output signal and the counters output signal, the counter controller means being defined further to include: gate means receiving the clock pulse output signal, the comparator controller means output signal, the overvoltage controller means output signal and the counters output signals and providing an output count-up signal and a clock pulse in response to an output signal indicative of signal presence in the processing channel and an overvoltage controller means output signal in a ''''low'''' state, an output count-down signal and a clock pulse in response to a received overvoltage controller means output signal in a ''''high'''' state, in response to at least one ''''low'''' counters output signal, and providing an output count-up signal and a clock pulse in response to a received output signal indicative of signal presence in the processing channel, in response to received counters output signals in the ''''high'''' state.

29. A bio-feedback apparatus for sensing the brain-wave potentials produced by a subject and providing feedback signals in response thereto, the apparatus comprising: brain-wave indicator means detecting and sensing the brain-wave potentials and providing an output signal responsive thereto; preamplifier means receiving the brain-wave indicator means output signal and providing an amplified output signal responsive thereto; passband filter means, having a predetermined passband, receiving the preamplifier output signal and providing an output signal responsive to a frequency component of the received signal within the filter means passband; zero crossing detector means receiving the passband filter means output signal and providing a ''''high'''' output signal in response to a positive going zero crossing of the passband filter means output signal and a ''''low'''' output signal in response to a negative going zero crossing of the passband filter means output signal; tachometer network means receiving the zero crossing detector means output signal providing an output signal proportional to the frequency of the received zero crossing detector means output signal; means receiving the tachometer network means output signal and providing an oscillating output signal having a frequency corresponding to a multiple of the frequency of the sensed potential indicated by the tachometer network means output signal; amplitude discriminator means receiving the passband filter means output signal and providing an output signal substantially proportional to the amplitude of the received passband filter means output signal; comparator controller means receiving the amplitude discriminator means output signal and providing ''''high'''' output signal in response to a received amplitude discriminator means output signal having a predetermined minimum duration, in one position thereof; bandpass controller means having a predetermined high and a predetermined low threshold setting and providing a ''''high'''' AND a ''''low'''' output signal, receiving the tachometer network means output signal and providing a ''''low'''' output signal in response to a received tachometer network means output signal within the high and the low threshold settings of the bandpass controller means, the bandpass controller means output signal connected to the comparator controller means and the comparator controller means providing the output signal therefrom in the ''''high'''' state of the bandpass controller means output signal; and feedback indicator means connected to the comparator controller means receiving the comparator controller means output signal and providing subject-perceivable feedback signals in response to a received ''''high'''' comparator controller means output signal.

30. The bio-feedback apparatus of claim 29 wherein the tachometer network means includes: an oscillator means having an ''''on'''' and an ''''off'''' condition, the oscillator means receiving the zero crossing detector means output signal and being biased in the ''''on'''' condition in response thereto providing an oscillator means output signal; and wherein the amplitude discriminator means is defined further to include: discriminator amplifier means receiving the passband filter means output signal and providing an amplified output signal responsive thereto; diode means, having a forward biased and a reverse biased condition, connected to and receiving the discriminator amplifier means output signal, the diode means being forward biased and conducting when receiving a positive going discriminator amplifier means output signal and being reversed biased and nonconducting when receiving a negative going discriminator amplifier means output signal; capacitor means receiving the discriminator amplifier means output signal and being charged in response thereto in a conducting condition of the diode means; memory capacitor means receiving the charge on the capacitor means when connected thereto; first gate means having an opened and a closed condition connected between the capacitor means and the memory capacitor means, the first gate means receiving the oscillator output signal via the tachometer network means and being biased open in response thereto connecting the capacitor means and the memory capacitor means; switching means connected to the capacitor means having an ''''on'''' and an ''''off'''' condition and receiving the zero crossing detector means output signal, the switching means being biased in the ''''on'''' condition in response to a received zero crossing detector means output signal in the ''''high'''' state discharging the capacitor means connected thereto; and second gate means having an opened and a closed condition connected to the memory capacitor means and to the amplitude discriminator means, the charge on the memory capacitor means biasing the second gate means opened and providing the amplitude discriminator means output signal.

31. The bio-feedback apparatus of claim 30 wherein the tachometer network means includes: switching means, having an ''''on'''' and an ''''off'''' condition, and receiving the tachometer oscillator means output signal and being biased ''''on'''' in response thereto; function generator means connected to the switching means and having a portion charged in the ''''on'''' condition of the switching means, the charged portion being discharged in the ''''off'''' condition of the switching means, the function generator means providing an output signal proportional to the frequency of the sensed brain-wave potential in the discharging condition thereof; memory capacitor means connected to the portion fo the function generator charged in the ''''on'''' condition of the switch means and receiving the charge discharged from the function generator means when connected thereto; and switching means connected to the function generator means and to the memory capacitor means, having an ''''on'''' and an ''''off'''' condition, the switching means receiving the oscillator means output signal of the tachometer network means and being biased ''''on'''' in response thereto connecting the discharging function generator to the memory capacitor means.

32. A bio-feedback apparatus for sensing the brain-wave potentials produced by a subject and providing feedback signals in response thereto, the apparatus comprising: brain-wave indicator means detecting and sensing the brain-wave potentials at two preselected sites, and providing a controlling channel output signal indicating the sensed brain-wave potential at each site; preamplifier means receiving the controlling channel output signals and providing amplified output signals responsive thereto; a plurality of processing channels, some of the processing channels receiving one of the controlling channel output signals and providing a feedback signal responsive thereto, some of the other processing channels receiving one other of the controlling channel output signals and providing a feedback signal responsive thereto, each of the processing channels comprising: frequency discriminator means, having a predetermined passband, receiving the preamplifier output signal and providing an output signal responsive to a predetermined frequency component of the received preamplifier output signal having a frequency within the passband of the frequency discriminator means; and means receiving the frequency discriminator means output signal and providing an output signal indicating signal presence in the processing channel, comprising: first audio means providing subject-perceivable audible feedback signals responsive to a received signal input thereto; second audio means providing subject-perceivable audible feedback signals responsive to a received signal input thereto; and switch means receiving the feedback signals of each controlling channel output signal and connected to the first and the second audio means, the switch means having one switch condition connecting the feedback signal from one controlling channel output signal to the first audio means and the feedback signal from one other controlling channel output signal to the second audio means, and one other switch condition connecting the feedback signals from one of the controlling channel output signals to the first and the second audio means.