COMMUNICATION BY ELECTROENCEPHALOGRAPHY; SPECIAL REPORT NO. 12

• Document Type: CREST
• Collection: STARGATE
• Document Number (FOIA) /ESDN (CREST): NSA-RDP96X00790R000100020029-5
• Release Decision: RIFPUB
• Original Classification: K
• Document Page Count: 12
• Document Creation Date: November 4, 2016
• Document Release Date: December 1, 2011
• Sequence Number: 29
• Publication Date: November 1, 1964
• Content Type: REPORT

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L AFCRL.64 910
NOVEMBER 1964
Special Reports
No. 12
r
Communication by Electroencephalography
E.M. DEWAN ;,
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The experiment reported here was performed in the Stanley Cobb Laboratories for Psychiatric Research
at Massachusetts General Hospital while the author was on leave of absence from
Air Force Cambridge Research Laboratories
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(MICROWAVE PHYSICS LABORATORY) PROJECT 5635
*(AIRFORCE CAMBRIDGE RESEARCH LABORATORIES) OFFICE OF AEROSPACE RESEARCH.(UNITED STATES AIR FORCE) L.G. HANSCOM FIELD, MASS.
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Abstract
The alpha rhythm can be blocked by visual concentration to control an electric
switch at will. This could in turn be used for purposes of control or communica-
tion directly via EEG signals-in other words, by thought manipulation. Although
practical applications of this idea have yet to be investigated, the actual demonstra-
tion of a thought-controlled device is in itself of interest.
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Communication by Electroencephalography
If a person could manipulate a switch simply by altering his thoughts in
some way, he could communicate with or control some part of his environment
without recourse to motor activity. Certainly, a device that could do this would
have a number of possible applications-for example, in the field of prosthetics.
Ideas of practical applications will be left to the reader, however, since a thought-
controlled device is of possible interest in itself, and this report will be confined
to a description of methods and equipment.
The main purpose of this note is to point out that under certain circumstances
a person can utilize well-known properties of the alpha rhythm to turn a switch on
and off merely by regulating his thoughts in a way to be described. To prove the
feasibility of such an approach, the author has used the electronic equipment
described below and has successfully turned a desk lamp on and off at will solely
by manipulating his own EEG. (This experiment has on several occasions been
successfully performed in the presence of an audience, one member of which was
asked to say "now" whenever he desired the lamp to be switched on or off. )
It is well-known among electroencephalographers that many individuals
possessing prominent alpha rhythms (10 cps approx.) can cause such activity to
"block" by opening their eyes, or even by keeping their eyes closed and concentrat-
ing on a vivid mental picture of some object, scene, or pattern. Such individuals
can turn their alpha waves on merely by "resting," or turn them off by thinking
(Received for publication 18 September 1964)
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visually. It is a relatively simple matter to amplify EEG voltages so that they can
trigger a relay-whenever the alpha rhythm is on, say; hence, such individuals
could signal by using Morse code, for example, merely by thought manipulation.
The following is a detailed description of the procedure used by the author as
the subject in the above-mentioned feasibility test (see Figure 1 for the general
diagram).
ATTEN SW
3K to II K to GND
POWERS 122
SUPPLY LOW HIGH
LOW HIGH
2 cps 50 cps
0-
IN OUT
I t 330 M OUT ?
KRON-HITE
BP FILTER
LOW HIGH
Sept 15eps
CATHODE
FOLLOWER
THRESHOLD SWITCH
C NC
Figure 1. Block diagram of integrating threshold switch
and associated equipment.
1. A pair of EEG scalp electrodes were attached to the occipital region in the
usual manner.
2. Two high-gain amplifiers (a Tektronix Type 122 low-level preamplifier and
a Tektronix RM 122 preamplifier) were connected in series and used to raise the
voltage of the alpha rhythm signal to 3 or 4 volts.
3. Next the signal was sent through a bandpass filter (Model 330M KRON-HITE
Bandpass Filter, 2 cps to 20 kcps),which had been set for a range of 9 to 15 cps.
4. A cathode follower was inserted to allow the signal to operate the next
device.
5. An integrating threshold switch (Figure 2) was activated whenever the
alpha rhythm was on for more than a very short duration.
Figures 3(a) and (b) show oscilloscope traces of the EEG during blocking and
alpha activity, respectively. It should be mentioned that these were obtained with
the help of a shielded chamber to cut down electrical interference. In contrast,
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Figures 4(a) and (b) show the filter-induced enhancement of the difference between
blocking and alpha activity. Under the ideal conditions of the experiment, there is
no ambiguity as to whether the alpha rhythm is on or off. The use of shielded
chambers might under most circumstances be avoided by using the filter.
There are several possible ways of modifying the equipment to improve both
the form and quantity of the information output. For example, there is no reason
in principle why the series of information bits could not be used to operate an
electromechanical typewriter such as could be provided by some sort of modified
and augmented* teletype machine.
The output might also be used to control electromechanical devices that could
manipulate things in the environment, such as a very crude "grasping" instrument.
An even further extension of this idea exists in the possibilities of increasing the
information output by using the right and left hemispheres of the brain independ-
ently.t It could even be speculated that a person could learn to modulate the
frequency of his alpha rhythm.
In summary, under certain circumstances it is possible for a person to manip-
ulate his EEG in a way that permits communication without motor activity.
*As pointed out in a private communication by Dr. F. Brooks of IBM, a special
purpose computer might be necessary to eliminate problems arising in communica-
tion with a mechanical device utilizing imperfectly timed coded signals. In other
words, it is not obvious how a device such as a teletype could "recognize" Morse
code signals with dots and dashes not having constant time values, unless some sort
of intermediate recognition device were added.
tThis idea was suggested by Dr. W. McCulloch of Massachusetts Institute of
Technology who pointed out that the alpha rhythm of the hemispheres could be inde-
pendently blocked by focusing attention on particular parts of the visual field.
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whalkwASEEMEN
if is LIrAIVAL MAEN,
MKIiIII MKIMBLIAMERIAMEI
Figure 3. Oscilloscope tracings of amplifier output: (a) alpha blocked, (b) alpha on.
(1 v per abscissa division and :10 cosec per ordinate di 7 ion)
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Figure 4. Oscilloscope tracings of amplifier output after filtering: (a)alpha blocked,
(b) alpha on. (1 v per abscissa division and 50 msec per ordinate division)
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1. An investigation of the channel capacity of this method of communication
has since elicited that an average of 16 to 20 sec per letter gives reliable commu-
nication with the present apparatus. (Morse code was used and the light was re-
placed by an audio oscillator.) The major difficulty seemed to be that hysteresis
in the threshold switch caused a gap of approximately 2. 5 v between the On and Off
thresholds. Presumably, this could easily be remedied, and many other refine-
ments could be made to enhance reliability and speed.
2. It has been brought to the attention of the author by reliable authority that
patients without any motor control whatever simply do not exist. Even if they can-
not move a muscle, they still have detectible electromyographic potentials that
could be utilized. Since it is likely that the resulting signals would be far more
reliable than those from modulated brain potentials, a computer converting -Morse
code into more useful outputs (such as teletype) might be much more efficient wheal
applied to electromyographic potentials than to EEG potentials. The use of EEG
for communication purposes therefore seems to have very little likelihood of
practical application at this time.
3. On the other hand it should be mentioned that there are epistemological
implications of this work with respect to the operational definition of consciousness,
for example, in the hypothetical case of a brain in vitro without efferent and affer-
ent connections. If such a preparation is assumed to have originally been part of a
human organism that could in its natural state use the method of communication
described in this report, then it could perhaps continue to respond meaningfully
to messages sent to it by direct cortical stimulation (say, to the auditory projec-
tion area). Assuming the responses were meaningful and consistent, then there
would be justification for concluding that the isolated brain was still conscious.
For further work on the epistemological problems of defining consciousness,
see "Other Minds: An Application of Recent Epistemological Ideas to the Definition
of Consciousness," by E. M. Dewan, in Philosophy of Science 24:70, January, 1957.
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Acknowledgments
The integrating threshold switch was designed and built for the experiment by
Capt. T. M. Purnhagen of the Microwave Physics Laboratory, Air Force Cambridge
Research Laboratories.
I am especially indebted to J. Witham for his assistance with usual problems
of sensitive electronic gear, and to Dr. F. Ervin of the Massachusetts General
Hospital for his encouragement of research in this direction; both are at the Stanley
Cobb Laboratories for Psychiatric Research at the Massachusetts General Hospital.
I am also indebted to Dr. Belmont Farley for very stimulating conversations
in which he described his work in the modification of brain wave activity by means
of conditioned responses.
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No. 1. Today's Meteorological Rocket Network and Atmospheric Problems of Aerospace Vehicles,
Norman Sissenwine, May 1964, (REPRINT).
No. 2. Ferrimagnetic Resonance Relations for Magneto crystalline Anisotropy in Cubic' Crystals,
Hans Roland Zapp, April 1964.
No. 3. Worldwide Collection and Evaluation of Earthquake Data, Final Report on Evaluation of 1960 Seismicity,
R.L. Fisher, R.G. Baker and R.R. Gaidroz, June 1964.
No. 4. Visual Observations Beneath a Developing Tornado, Ralph 1. Donaldson, Jr. and William E. Lamkin,
August 1964 (REPRINT).
No. 5. Bibliography of Rock Deformation, R.E. Riecker, 1/Lt, USAF, September 1964.
No. 6. The Modification of Electromagnetic Scattering Cross Sections in the Resonant Region, A Symposium Record,
Volume I, J.K. Schindler, 1/Lt, USAF, R.B. Mack, Editors, September 1964.
No. 6. The Modification of Electromagnetic Scattering Cross Sections in the Resonant Region(U),
A Symposium Record, Volume II, J.K. Schindler, 1/Lt, USAF, R.B. Mack, Editors, September 1964 (SECRET).
No. 7. The Natural Environment for the Manned Orbiting Laboratory System Program (VIOL), 25 October 1964.
No. 8. The Vertical Transfer of Momentum and Heat At and Near the Earth's Surface, Morton L. Barad,
October 1964 (REPRINT).
No. 9. Bibliography of Lunar and Planetary Research-1963, I.W. Salisbury, R.A. VanTassel, I.E.M. Adler,
R.T. Dodd,Jr., and V.G. Smalley, November 1964.
No. 10. Hourly Rawinsondes for a Week (Part 11), Arnold A. Barnes, Jr., and Henry A. Salmela,
November 1964.
No. 11. An Appraisal of Rayleigh, John Howard, Editor, November 1964 (REPRINT).
No. 12. Communication by Electroencephalography, E.M. Dewan, November 196.1.
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