Table Of ContentTHE EFFECT OF CERTAIN MENTAL OPERATIONS
UPON THE ALPHA RHYTHM
A Dissertation
Presented to
the Faculty of the Graduate School
The University of Southern California
In Partial Fulfillment
of the Requirements for the Degree
Doctor of Philosophy
by
George Donald Gray
February 1950
UMI Number: DP30390
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TABLE OF CONTENTS
CHAPTER PAGE
I. INTRODUCTION................'........... 1
Psychology and the E E G ................. 4
Types of waves, constituting the EEG . . 4
Variables of the EEG and their measurement 7
Characteristics of the alpha waves . . . 10
The origin of the alpha waves.......... 29
Characteristics and origin of beta waves 32
Characteristics and origin of delta waves 37
Characteristics and origin of kappa waves 41
Relationship between records of the two
hemispheres......................... 42
Underlying factors in brain rhythms . . . 44
The brain rhythm and mathematical biophysics 65
II. THE PROBLEM............................. 68
III. REVIEW OF THE LITERATURE............... 70
IV. APPARATUS, SUBJECTS, AND PROCEDURE . . . . 85
Bipolar versus monopolar recording . . . 87
Artifacts............................. 89
Recording equipment .................... 92
Recording room.............. 92
Electrodes and their placement ........ 93
Subjects and procedure ................. 94
Analysis of data*....................... 95
CHAPTER PACE
V. RESULTS................................. 98
VI. DISCUSSION . . ....................... . . 129
Analysis of this s t u d y ....................... 129
Comparison with former studies ............... 133
VII. SUMMARY AND CONCLUSIONS.................. 141
Summary............................... 141
Conclusions . . . . . . . 143
BIBLIOGRAPHY...................................... 146
APPENDIX A. The tests......................... 159
APPENDIX B. A section of record................ 161
LIST OF TABLES
TABLE PAGE
I. Alpha Wave Count for Twenty Seconds of
Record ..................... 99
II. Alpha Index for Twenty Seconds of Record .■ . . 101
III. F.-Test and t-Test Results................. 105
IV. F-Tests C A R .....................112
V. t-Tests C A ................................... - 114
VI. t-Tests C R ................................. 117
VII. t-Tests A R ................................. 118
VIII. t-Tests CA Number.......................... 120
IX. t-Tests CR Number.......................... 122
X. t-Tests AR Number.......................... 123
XI. t-Tests CA Language........................ 124
XII. t-Tests CR Language........................ 125
XIII. t-Tests AR Language ...................... 127
XIV. LR Control............... 128
CHAPTER I
INTRODUCTION
Definite knowledge of the electrical properties of
living tissue began with the investigations of Du Bois-Reymond
(49), which resulted in the discovery of the demarcation and
action current in muscle and nerve in 1843. In 1874, Caton
(30) discovered evidences of electrical activity in the brains
of living animals. Throughout the years to 1924 various ani
mal studies were reported, but in this year Berger (9) suc
ceeded in recording the activity of the human brain. In 1925,
Neminski (123), working on the electrical activity of the cor
tex of the dog, coined the work electrocerebrogram to describe
the spontaneous fluctuations in potentials which he observed.
In his electrocerebrogram, which he was able to obtain from
the cortex itself, the dura, and the outer surface of the
skull, he distinguished spontaneous fluctuations in potential
with a frequency of 10-15 waves per second, and other faster
fluctuations of 20-32 waves per second. The former he called
waves of the first order and the latter waves of the second
order. Berger, apparently a purist, changed the second root
in electrocerebrogram, and referred to his record as the
elektrenkephalORramm. which is usually rendered into English
as electroencephalogram and abbreviated EEG-.
During the ensuing years, particularly 1929-33,
2
Berger (9,12,13,14->15) carried out the first systematic study
of the EEG- of human subjects. He made several important dis
coveries and proposed some theories. He noted that the spon
taneous rhythm is recordable from, the surface of the intact
skull of the conscious human subject, and that the rhythm
gives the greatest effect over bone defects in the skull. He
further noted that the same frequency rhythm is obtainable
over most any part of the haad and with particular prominence
over the occiput, and that, for the entire head between elec
trode pairs, there were always secondary fast rhythms super
imposed on the slower dominant ones. To these slow dominant
rhythms, most prominent over the occiput and having a fre
quency of about 10 vibrations per second, he gave the name
aloha waves; and to the superimposed low amplitude, higher
frequency activity he applied the name beta waves. He con
cluded that the alpha rhythm originates in the cortex, that
it represents a fundamental activity of the brain, and that
it has a wide and less specific origin than the occipital
lobes — that every part of the cortex may contribute to the
recorded potential changes. He ruled out the possibility
that the waves come from the blood vessels or connective tis
sue; and concluded that the alpha rhythm results from the
activity of a large mass of neurons in the cortex as a whole,
and that it is a reflection of biologic activities associated
with psychophysical processes.
3
Berger found that the alpha waves appear most favor
ably when the subject is lying quietly with his eyes closed;
and that the rhythm can be modified by the application of
sensory stimuli, or by having the subject engage in some
thing that occupies his whole attention, e.g., a problem in
mental arithmetic. He noted in these situations that beta
waves are apparently unaffected, and concluded that they
arise from nutritive and metabolic functions. It was posited
that attention to specific sensory stimuli is associated
with facilitative processes in one specific locus of the
cortex, and inhibition of activities in all other parts.
Depression of the alpha rhythm reflects this process of in
hibition in the greater part of the cortex.
Adrian and Matthews (2) confirmed the work of Berger,
but disagreed as to the locus of the alpha rhythm, contend
ing that the rhythm is occipital in origin. They even sus
pected that muscle potentials picked up by the scalp might
account for the record. Accordingly, they conducted an ex
tensive study, in which they were able to rule out muscle
sources, but in which they became further convinced that
the rhythm was entirely occipital in origin. In fact, they
applied the expression f,Berger rhythm” to the occipital alpha
waves in order to distinguish them from Berger's alleged
over-the-whole-cortex alpha rhythm.
4
I. PSYCHOLOGY AND THE EEG
It is well established that the EEG reflects physio
logic activity in the brain. If factors in the brain on
which the EEG depends are also factors in psychological phe
nomena, them the EEG might be an indicator of physiologic
mechanisms underlying psychological phenomena. If this be
true, then it lies within the province of the psychologist
to look into the nature of the brain activities which regu
late psychological performance. The suggested steps to be
followed are (a) a determination of an empirical correlation
between any psychologic variables and some property of the
EEG; if the result is positive, then (b) a determination of
the factors in the brain which are responsible for the partic
ular type of EEG obtained; and then, (c) the formulation of
a working hypothesis of the role played by these factors in
the psychologic phenomena under consideration (104).
II TYPES OF WAVES CONSTITUTING THE EEG
The alpha waves. With respect to frequency, the
upper and lower limits and the range assigned to these waves
are somewhat arbitrary. The lowest and highest limit and
the broadest spread are allowed by Narrow (36), who gives
7-14 waves per second; the other extreme is found with Adrian
and Matthews (2), who give 9.5-10.5 waves per second. It is
generally agreed that the waves have a frequency of about 10
