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Patent No. 4227516
Apparatus for electrophysiological stimulation (Meland, et al., Oct 14, 1980)
Abstract
Apparatus for the electrophysiological stimulation of a patient is provided for creating an analgesic condition in the patient to induce sleep, treat psychosomatic disorders, and to aid in the induction of electrohypnosis and altered states of consciousness. The foregoing is achieved by repetitive stimuli in the patient for whom external influences, namely those of sight and sound, are intentionally excluded. The apparatus produces electrical stimulation of the patient in the form of a modulated wave which produces impulses in the delta, theta, alpha and beta regions of the brain's electrical activity, the electrical stimulation being accompanied by two sources of audio stimulation, one of which is a sinusoidal tone modulated by and synchronized with the electrical stimulation, and the other is derived from sound recordings.
What
is claimed is:
1. A system for producing electrophysiological stimulations in a patient so
as to stimulate the effects of brain wave activity in at least one of the delta,
theta, alpha and beta frequency ranges, said system including: first means for
generating a first wave in a predetermined frequency range extending above the
delta, theta, alpha and beta frequency ranges; second means for generating a
second wave in at least one of said delta, theta, alpha and beta frequency ranges
and connected to said first means to cause the first wave to be modulated by
the second wave to cause the first means to produce bursts of the first wave
occurring at the frequency of the second wave; and means connected to the first
means for introducing the bursts of the first wave from the first means to electrode
means mounted on the forehead of the patient for the electrophysiological stimulation
of the patient.
2. The system defined in claim 1, in which said first and second means each
comprises an astable multivibrator, and in which said first and second waves
are square waves.
3. The system defined in claim 2, in which said first means generates the first
square wave in a frequency range extending substantially from 23 to 50 Hz.
4. The system defined in claim 2, in which said second means includes manually
adjustable means for setting the frequency of the second wave selectively to
the delta, theta, alpha and beta frequency ranges.
5. The system defined in claim 2, in which said second means includes manually
adjustable means for controlling the shape and symmetry of the second square
wave.
6. The system defined in claim 1, and which includes potentiometer means connected
to the second means for controlling the amplitude of the modulated wave introduced
to the electrode.
7. The system defined in claim 1, and which includes third means for generating
a sinusoidal tone signal in a range extending substantially from 150-600 Hz,
and including means connected to said second means for modulating the tone signal
in synchronism with the second wave generated by the second means; and further
means connected to said third means for applying the modulated tone signal to
headphones worn by the patient.
8. The system defined in claim 7, in which said third means includes manually
controllable means for adjusting the degree of modulation of said tone signal
by said second wave.
9. The system defined in claim 7, in which said third means includes manually
controllable means for adjusting the frequency of said tone signal.
10. The system defined in claim 7, in which said third means includes manually
controllable means for adjusting the volume of the modulated tone signal.
11. The system defined in claim 7, and which includes fourth means connected
to said further means for introducing prerecorded sounds to the headphones.
12. The system defined in claim 1, and which includes battery means for energizing
the system; and which further includes charging circuitry for the battery means,
and control circuitry for de-energizing the system whenever the charging circuitry
is active.
13. The system defined in claim 1, and which includes switching means to be
held in the hand of the patient to de-energize the system should the stimulation
produced by the system become uncomfortable.
14. The system defined in claim 13, and which includes buzzer means connected
to the system to be energized when the system is de-energized by said switching
means.
15. The system defined in claim 1, and which includes pre-settable timer circuitry
for determining the time during which the system is to be activated.
BACKGROUND
Methods and apparatus are known for inducing sleep, treating psychosomatic disorders,
and for aiding in the induction of hypnosis in a patient, the foregoing being
achieved by passing a stimulation of electrical current pulses through the brain
of the patient by electrodes attached, for example, to the back of the head
and to the forehead. Such apparatus is described, for example, in U.S. Pat.
No. 3,762,396. In the apparatus described in the patent, the electric current
impulses of the stimulus have a frequency of 8-10 Hz. The apparatus described
in the patent also passes a second stimulus of electric pulses to the brain
of the patient having a frequency which is four times the frequency of the pulses
of the first stimulus, the latter stimulus being introduced through the optic
nerves of the patient by the electrodes attached to the temple and forehead.
A third auditory stimulus is provided in the system described in the patent
by way of sound attenuating chambers. The auditory stimulus is used acoustically
to isolate the patient from a noise environment. The three stimuli are preferably
synchronized with one another.
U.S. Pat. No. 3,908,634 describes a method and apparatus for inducing a vocalized
analgesic condition in the patient by simulating the presence of a hypnotherapist.
This is achieved by reproducing a recording of the speech that the hypnotherapist
would normally make to the patient.
The apparatus of the present invention falls in the same general class as the
apparatus described in the above-mentioned patents; and an objective of the
apparatus of the invention, likewise, is to produce different states of consciousness
in a patient by repetitive stimuli, with the patient being insulated from external
influence. In the practice of the invention, the patient to all intents and
purposes is placed in a closed chamber in which the apparatus is set to an operational
mode which creates a sensory input; and impulses in the delta, theta, alpha
and beta ranges are introduced to the optic cortex, each producing its specific
state of consciousness in the patient.
The various ranges referred to above relate to the different rhythms in the
brain's electrical activity. For example, the alpha rhythms have a pulse frequency
in the 8-13 Hz range; the beta rhythms have a pulse frequency in the 13-30 Hz
range; the theta rhythms have a pulse frequency in the 4-7 Hz range; and the
delta rhythms are slow waves with pulse frequencies in the 0.5-3 Hz range. The
alpha rhythms are customarily found in the normal human adult when he is relaxed
and has his eyes closed; the beta rhythms are normally encountered when a person
is aroused and anxious; the theta rhythms are often found in adolescents with
behavior disorders; and the delta rhythms appear in the normal person when he
is asleep.
Each impulse introduced to the patient by the apparatus of the invention is
super-imposed on the brainwave activity, finally dominating it and thereby altering
the patient's state of awareness. The result is light or deep sleep, somnolence,
hypnosis, heightened awareness, or even agitation, depending upon the frequency
of the pulses introduced to the patient.
The electrical stimulation is in the form of a modulated square wave accompanied
by two sources of audio stimulation, one of which is a sinusoidal tone, modulated
by and synchronized with the optical electrical stimulation. The other audio
sound helps to overwhelm the circuits, minimizing internal and external inputs.
The subject is restricted to the selective sensory impulses he is receiving,
and he shuts out most of his internal and external environment, the result being
that the impulses received alter the patterns of brain activity essentially
bringing the brain into synchronism with the instrument.
Specifically, the present invention provides an improved instrument constructed
for electrophysiological stimulation of a human being. The instrument is capable
of inducing into the patient the effects produced by brainwave activity in the
delta, theta, alpha and beta ranges. The apparatus uses a modulated square wave
which creates the electrophysiological stimulation, and which is accompanied
by two sources of audio stimulation, one being synchronized with the electrophysiological
stimulation. The electrical stimulation is applied to the patient by means of
electrodes attached to the forehead.
The audio stimulation is introduced to the patient by means of headphones. One
of the audio stimuli is a sinusoidal tone modulated by and in synchronism with
the electrophysiological stimulation. The other audio stimulus is derived from
a cassette tape player, which plays pre-recorded tapes of special sound effects
or hypnotic suggestions recorded for a specific patient.
The result of the foregoing three stimulating forces acting together enables
the instrument to alter the mood or mental state of the patient so as to produce
a variety of altered mental states. The instrument of the invention can be used,
for example, for inducing sleep, inducing an hypnotic state, producing tranquility
and relaxation, producing heightened awareness, increasing the ability of a
person to concentrate, and for inducing other mental states. The instrument
can also be used for treating psychosomatic disorders.
The instrument to be described is battery operated from a self-contained rechargeable
12-volt battery. Battery operation is used for electrical safety, since it completely
eliminates the possibility of a patient being electrocuted, as could occur with
alternating current line operated equipment.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of an instrument representing one embodiment of the
invention; and
FIGS. 2 and 2A represent a circuit diagram of the instrument of FIG. 1.
DETAILED DESCRIPTION OF THE ILLUSTRATED
EMBODIMENT
The system of the invention includes a block designated 10 which is the nucleus
of the system. This block is an astable multivibrator which generates square
waves of variable frequency and shape. The multivibrator of block 10 performs
three functions: (1) it controls or synchronizes the output of a modulation
multivibrator represented by block 12; (2) it controls or synchronizes the output
of a tone generator represented by block 14; and (3) it produces square wave
output pulses which can be used as the stimulating voltage applied to the patient
by way of electrodes connected to a jack 16.
The square wave output from the multivibrator of block 10 appears on a lead
18 which is connected to one of the fixed contacts of a switch S2. The modulated
pulse output of the modulation multivibrator of block 12 appears on a lead 20
which is connected to the other fixed contact of switch S2. The armature of
switch S2 is connected to a grounded potentiometer R8 and to a fixed contact
of a switch S3. The armature of potentiometer R8 is connected to a grounded
voltmeter M1, and through an ammeter M2 to jack 16 which receives an appropriate
plug to connect the circuit to an electrode on the forehead of the patient.
The output of tone generator 14 is connected to a second fixed contact of switch
S3, and the armature of the switch is connected to an oscilloscope represented
by the block 30.
The synchronized sinusoidal tone derived from the tone generator of block 14
is applied to a tape player and amplifier 22 so as to synchronize one of the
outputs from the amplifier with the square wave pulses from the multivibrator
10. A further meter designated M3 is connected to the tape player and amplifier
22. The synchronized sinusoidal output from the tape player and amplifier 22
is applied to one of the contacts of a headphone jack 24. The recorded message
of hypnotic suggestions for the specific patient is also recorded in the tape
player, and signals representing these messages are introduced to a second contact
on jack 24. New messages may be recorded by a microphone having a plug which
is plugged into a microphone jack 26.
Direct current power for the instrument is provided by control circuits represented
by the block 32, the control circuits also controlling a buzzer 34, and being
controlled by a timer 36. A remote control may also be connected to the control
circuits by way of a jack 38. The control circuits are activated by a 12-volt
battery 40 which is maintained in a charged condition by a battery charger 42,
the battery charger being energized by the usual 115-volt alternating current
voltage derived from the usual alternating current mains.
As shown in FIG. 2A, the multivibrator 10 includes a pair of NPN transistors
Q1 and Q2 which are interconnected through a 10 kilo-ohm potentiometer R1, a
3.9 kilo-ohm resistor R2, a 2.2 kilo-ohm resistor R3, a 50 kilo-ohm potentiometer
R4, a 4.7 kilo-ohm resistor R5, a 4.7 kilo-ohm resistor R6, and a 470 ohm resistor
R7. The multivibrator 10 also includes a two-pole operator control switch S1
which makes selective contact with a first group of capacitors C1, C2, C3, C4
and C5 having respective capacities of 1, 1.9, 4.5, 10.7 and 39 microfarads,
and a second group of capacitors C6, C7, C8, C9 and C10 having respective capacitires
of 1, 1.9, 4.5, 10.7 and 39 microfarads. Also included in the circuit of multivibrator
10 is a 1000 microfarad capacitor C27 and a 250 microfarad capacitor C11.
The modulation multivibrator 12 includes a pair of NPN transistors Q5 and Q6
which are interconnected through a pair of diodes CR6 and CR7, and through a
10 kilo-ohm resistor R21, a 4.7 kilo-ohm resistor R22, a 2.2 kilo-ohm resistor
R23, a 47 kilo-ohm resistor R25, a 47 kilo-ohm resistor R26, a 50 kilo-ohm resistor
R27, and a 470 ohm resistor R29. Also included in the multivibrator circuit
are a 0.33 microfarad capacitor C17, a 0.33 microfarad capacitor C18, and a
50 microfarad capacitor C19.
The capacitor C11 of the multivibrator 10, and the capacitor C19 of the modulation
multivibrator 12 are connected to a switch S2 which, in turn, is connected to
the jack 16 through the meters M1 and M2.
The switch S3 associated with oscilloscope 30 is connected to the junction of
a 240 kilo-ohm resistor R30, and a 68 kilo-ohm resistor R31, the resistors being
connected between one of the contacts of switch S2 and ground, as shown.
The multivibrator 10 is connected through a 47 kilo-ohm resistor R61 to a 7.5
kilo-ohm potentiometer R9, the latter potentiometer being included in the circuit
of tone generator 14. The tone generator includes a pair of NPN transistors
Q3 and Q4 which are interconnected by a 4.7 kilo-ohm resistor R10, a 15 kilo-ohm
resistor R11, a 150 kilo-ohm resistor R12, and a 3.3 kilo-ohm resistor R13.
Also included in the circuit are a 500 microfarad capacitor C28 and a 0.1 microfarad
capacitor C12.
The transistor Q4 is connected to a resistance-capacitance network which includes
a 1 kilo-ohm resistor R14, and a pair of 0.15 microfarad capacitors C13 and
C14. The transistor Q4 is also connected to a 4.7 kilo-ohm resistor R17, a pair
of 10 kilo-ohm potentiometers designated R16, and a 4.7 kilo-ohm resistor R15.
Also included in the latter network are a 0.01 microfarad capacitor C30 and
a 0.1 microfarad capacitor C15. The circuit also includes a 25 kilo-ohm potentiometer
R20, a 100 kilo-ohm resistor R19, and a 15 kilo-ohm resistor R70. Included in
the latter circuit are a 0.01 microfarad capacitor C29 and a 0.22 microfarad
capacitor C16.
The battery charger circuit 42 is of usual construction, and has a circuit such
as shown in FIG. 2B. This circuit is used to maintain a full charge on battery
40. The battery is connected to the control circuits 32 through a switch S5,
and through a switch S6. The control circuits include relays K3 and K5, one
pair of contacts of relay K3 being connected to the buzzer 34. The control circuits
also include a 1 kilo-ohm potentiometer R51, and a pair of 68 ohm resistors
R52 and R53. A further relay K4 is also included in the control circuit, as
are a pair of indicating lights I4 and I5. Relay K3 is connected to jack 28
which receives a remote control for the system.
The control circuits 32 also include a unijunction transistor Q7, and a silicon
controlled rectifier Q8. The unijunction transistor may be of the type designated
2N6027, and the silicon controlled rectifier may be of the type designated C103.
Associated with the unijunction transistor and the silicon controlled rectifier
are a 100 ohm resistor R49, a 3.3 megohm resistor R50, a 2.2 megohm resistor
R65, a 1 megohm potentiometer R66, a 1 megohm resistor R67, a 1 megohm resistor
R68, and a 1 kilo-ohm resistor R69. Also included in the control circuits are
a pair of diodes CR8 and CR9, a capacitors C21, a 0.001 microfarad capacitor
C24, a 1 microfarad capacitor C25, and a 0.01 microfarad capacitor C26. A blank
transistor Q9 is also included in the circuit, and may be of the type designated
TIS43.
The control circuits are connected to the timer 36 through diode CR8, and through
a further diode CR10. The latter diode is connected to the positive terminal
of a 12-volt source through a 680 ohm resistor R47. The timer comprises a series
of 1 megohm resistors R35-R46, and a switch S4 which is controllable to connect
selectively with the junctions between the resistors.
The tape player and amplifiers 22 include a pair of amplifiers A1 and A2. Inputs
from the microphone plugged into jack 26 are amplified in an amplifier including
an NPN transistor Q10. The amplifier includes a 10 kilo-ohm resistor R58, a
4.7 kilo-ohm resistor R72, a 470 ohm resistor R43, and 82 kilo-ohm resistor
R74 and a 10 kilo-ohm resistor R75. The amplifier also includes a 10 microfarad
capacitor C32, a 100 microfarad capacitor C33, and a 1000 microfarad capacitor
C31. A voice volume 10 kilo-ohm potentiometer R58 is connected across the output
of the amplifier, and is connected to the junction of a pair of 22 kilo-ohm
resistors R56 and R57 which, in turn, are connected to the inputs of the amplifiers
A1 and A2. The tone volume control potentiometer R20 of the tone generator 14
is connected to a pair of 22 kilo-ohm resistors R54 and R55 which, likewise,
are connected to the inputs of the amplifiers. The amplifiers are connected
to the headphone jack 24 through a pair of 220 ohm resistors R76 and R77, and
to a pair of 4 ohm resistors R59 and R60. The amplifiers are also coupled to
audio level meter M3 through a pair of 50 microfarad capacitors C22 and C23,
through a transformer T2, and through a 33 kilo-ohm resistor R78.
The frequency range of multivibrator 10 is controlled by the operator control
switch S1, to set the frequency in the "delta low", "delta hi",
"theta", "alpha" and "beta". The frequency is
more precisely adjusted in each of the aforesaid ranges by the operator control
potentiometer R1. The shape, or symmetry of the square wave is adjusted by the
operator control potentiometer R4.
When the pulses from potentiometer 10 are used as the stimulating voltage, the
operator control switch S2 is set to the upper position designated "normal".
The amplitude of the pulses generated by the multivibrator are controlled by
the operator control potentiometer R8. The voltage and current output are monitored
by the control panel meters M1 and M2 respectively, with M1 monitoring the electrode
voltage, and M2 monitoring the electrode current. The square wave output at
jack 16 is an alternating current, whose direct current component is blocked
by capacitor C11.
If desired, oscilloscope 30 may be incorporated into the circuit so that the
actual square wave shape may be observed, and so that its frequency may be measured.
The electrodes which are attached to the patient's forehead by means, for example,
of a rubber strap, receive their voltage by means of suitable wires connected
to the jack 16. The modulation multivibrator 12, like modulator multivibrator
10 is an astable multivibrator. Multivibrator 12 is similar to multivibrator
10 except that it has a limited frequency range, and in that it has a fixed
pulse shape which is a symmetrical square wave. The frequency range of multivibrator
12 is from 23 to 50 Hz, and the frequency is controlled by the operator control
potentiometer R21. The output voltage of modulation multivibrator 12 is turned
on and off by square wave pulses received from multivibrator 10. These controlling
pulses are applied to the base of transistor Q6 causing it to become conductive
and thereby stopping the multivibrator action during each positive pulse. The
negative pulses are blocked from the base of transistor Q6 by diode CR3.
The net result is the effect of a modulated output from multivibrator 12 which
consists of bursts of higher frequency square waves, the burst rate being controlled
by multivibrator 10. The output of multivibrator 12 can be used as the stimulating
voltage, when the output is selected by the control switch S2, when the control
switch is switched to its lower position. The amplitude of the output from the
modulation multivibrator 12 is controlled by the same potentiometer R8 which
also controls the output from multivibrator 10. The same meters M1 and M2, and
oscilloscope 30 monitor the output from the modulation multivibrator 12, and
the output is available at the same jack 16, for application to the electrodes
on the head of the patient.
The frequency of 23-50 Hz of each burst produced by the modulated multivibrator
12 produces the maximum amount of flicker images in the optic system of the
patient. The output of multivibrator 12 is also an alternating current signal,
with the direct current component being blocked by the capacitor C19.
The tone generator 14 is a sinusoidal tone generator, the output of which can
be varied in frequency by the operator control potentiometer R16 over a range
of 150-600 Hz. The tone is modulated by the square wave output of multivibrator
10. The controlling pulses from multivibrator 10 are applied to the base of
transistor Q4. Each positive pulse from the multivibrator renders the transistor
Q4 conductive, either partially or completely to saturation, thereby slightly
changing the frequency or completely stopping the oscillation of the tone generator.
The degree of modulation is adjustable by the operator control potentiometer
R9. This potentiometer can be adjusted for complete turn-off producing tone
bursts or partial turn-off producing an undulating tone. The potentiometer can
also be adjusted for zero modulation producing a continuous steady tone. The
volume of the tone can be adjusted by the operator control potentiometer R20.
Since the tone generator is controlled by the output of multivibrator 10, its
output is in exact synchronism with the stimulation produced by the electrodes
plugged into jack 16. The three controls, namely tone frequency, tone modulation
and tone volume can therefore be adjusted by the operator for the most desirable
and optimum audio stimulation.
The tape player of block 22 is a stereo cassette tape player, and the block
also includes the stereo audio amplifiers A1 and A2. The details of the tape
player and amplifiers are not described herein, as they are conventional. The
tape player plays standard cassettes of pre-recorded sound effects or vocal
suggestions recorded for a specific patient. The amplifier transistor Q10 is
used to amplify the microphone input from jack 26, so as to enable the operator
to communicate directly with the patient. The output from the amplifier is transmitted
to the patient by means of the stereo headphones which are plugged with jack
24.
The output of the tape player is amplified by amplifiers A1 and A2, prior to
being introduced to jack 24. The amplifiers A1 and A2 also serve to amplify
the tone signals received from the tone generator 24. The output level of all
the audio sources is monitored by the control panel meter M3.
All of the control and logic circuitry is contained in block 32, and this circuitry
provides automatic controls for charging the battery 40. The control circuit
also provides a safety interlock which makes the overall system inoperative
whenever the power is connected to the alternating current power line, rather
than to the battery. The control circuit receives inputs from a hand held switch
S8, and from the timer 36. The timer can be set by adjustment of switch S4.
The patient holds switch S8 during therapy, and if the stimulation should become
uncomfortable for any reason, the patient can operate the switch which momentarily
removes power from relay K3 thereby causing the relay to unlatch removing power
from all circuits and energizing buzzer 34 to call the operator. When the pre-set
time interval of timer 36 has elapsed, the relay K3 unlatches with the same
results.
The indicator lights I1 and I2 are mounted on the control panel to indicate
the following conditions to the operator: (a) the indicator light I1 is energized
whenever the alternating current power cord is connected to the power line.
(b) The indicator lamp I5 is energized when the operator control switch S5 is
switched to the on position, and the operator control switch S6 is momentarily
depressed. This causes the relay K3 to pull in and "latch" itself
in the energized position turning power on to all circuits. (c) The indicator
lamp I4 is energized when the batteries are discharged to a point that they
are usable only for about two more hours of operation. (d) The indicator lamp
I3 is energized when the alternating current power cord is connected and the
batteries are being charged. (e) The indicator lamp I2 is energized when the
batteries are fully charged.
The battery 19 may be a rechargeable battery pack consisting of two or three
parallel connected batteries, each of which has a capacity, for example, of
4.5 ampere hours.
The battery charger 42 may be a conventional circuit.
When the battery voltage drops, for example, to 11.5 volts, indicator lamp I4
in the control circuit 32 is energized, as relay K4 drops out. Relay K4 may
be adjusted to drop out at 11.5 volts by potentiometer R51. The battery charge
circuit 42 includes an indicator lamp I1 which is energized when the alternating
current cord is connected to the line. The circuit also includes an indicator
lamp I2 which turns on when battery 40 is fully charged, and an indicator lamp
I3 which is energized while the battery is being charged. The charger circuit
includes a relay K1 which is energized when the charger is operating, and which
disconnects the battery 40 from the system of the invention, and connects it
across the battery. The circuit also includes a relay K2 which is energized
when the battery 40 is fully discharged, and which, when energized, introduces
a 47 ohm resistor R34 into the charging circuit which reduces the charging current
sufficiently so that battery 40 is merely maintained in a fully charged condition.
The timer 36 is adjustable, for example, in five minute increments from five
minutes to sixty minutes by operation of the control switch S4. The time interval
selected begins when the operator control switch S6 marked reset is momentarily
depressed. At the end of the time interval selected, relay K5 pulls in, removing
power from relay K3 and causing it to unlatch, effectively turning off all power
and turning on buzzer 34 to call the attention of the operator.
The timer circuit 36 utilizes the resistance-capacitance time charging principle.
Capacitor C21 is the timing capacitor, and resistors R35-R46 are the timing
resistors. When capacitor C21 charges up to a sufficiently high voltage, unijunction
transistor Q7 is rendered conductive, and applies a trigger pulse to the gate
of silicon controlled rectifier Q8, rendering the silicon controlled rectifier
conductive. When silicon controlled rectifier Q8 is rendered conductive, it
energizes relay K5, producing the results described above. The transistor Q7
is a programmable unijunction transistor, whose intrinsic stand-off ratio is
adjusted by potentiometer R66, and which provides a means for calibrating the
timer.
A field effect transistor Q9 is connected as an oscillator which provides sampling
pulses at the rate, for example, of one per second, and each having a duration
of 10 microseconds. These pulses are applied to the gate of transistor Q7, to
cause Q7 to become conductive for the duration of one such pulse, when the potential
across capacitor C21 exceeds a predetermined threshold. This sampling circuit
materially reduces the trigger current required to render the transistor Q7
conductive. Between pulses, the transistor Q7 is isolated from the capacitor
C21 by diode CR8, which is a low leakage diode, thereby eliminating any loss
of charging current due to leakage through the transistor Q7.
The invention provides, therefore, an improved instrument for electrophysiological
stimulation of a patient, and which is constructed to produce stimulation and
to stimulate the effect produced by brain wave activity in the delta, theta,
alpha and beta range.
It will be appreciated that although a particular embodiment of the invention
has been shown and described, modifications may be made. It is intended in the
claims to cover the modifications which come within the spirit and scope of
the invention.