Schizophrenia and EEG spectral analysis

Electroencephalography and Clinical Neurophysiology, 1974, 36:377-386 ( Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands

377

SCHIZOPHRENIA AND EEG SPECTRAL ANALYSIS 1 DUILIO GIANNITRAPAN! 2 AND LAWRENCE KAY1-ON 3

Hhlhland He,spiral. Duke UnirersiO. Asherille. N.C. 28801 (U.S.A.) [Accepted for publication: October I i, 1973}

This study was undertaken to explore the existence of relationships between EEG features and schizophrenia and to suggest some theoretical formulations applicable to the study of such relationships. Findings using traditional clinical interpretation of the EEG were summarized by Small and Small (1965) with the conclusion that EEG abnormalities among schizophrenics ranged from 5 to 807~. A review of these findings raised the possibility that the studies with a high percentage of EEG abnormalities had included a percentage of braindamaged subjects whose EEGs were abnorma! for neurological reasons. Further research into the EEG of schizophrenia required a methodology going beyond visual inspection of the records as well as a more sophisticated method for the diagnosis of schizophrenia. The technique of early spectral analysis for these studies has been most strongly identified with Kennard and her group who demonstrated that the records of schizophrenics showed a great incidence of fast activity (Kennard et al. 1955). This finding had been reported already by Finley and Campbell (1941), among others who used conventional techniques. Kennard and Schwartzman (1957) reported as well that schizophrenics have less sharply defined alpha activity than control subjects and a tendency toward lack of synchrony between homologous brain areas. i Research was conducted at the Psychosomatic and Psychiatric Institute for Research and Training of the Michael Reese Hospital and Medical Center and was supported in part by U.S. Public Health Service Grant MH-5519. -' Present address: Highland Hospital Division. Duke University Medical Center, Asheville, N.C. 3 Michael Reese Psychosomatic and Psychiatric Institute, Chicago, Ill.

The development of period analytic techniques dispelled some of the difficulties encountered by electronic spectral analysis. Period analysis, introduced by Saitzberg and Burch (1956), has been used by Lester and Edward~ (1966) to observe the fast activity of schizophrenics and by Fink et al. (1967) and ltil et al. (1972) in research on the psychopharmacology ofschizophrenia. Spectral analysis, without the shortcomings of electronic resonating filters, became possible with high-sp~-d digital computers (Brazier 1965). A major weakness in this area of research, however, remains, i.e., the lack of theory concerning the relationships between EEG and psychopathology. Investigations are necessarily restricted to an exploratory function, and findings need replication. An understanding of the processes involved can only be reached following adequate theoretical formulations. The present study was designed with a broad spectrum scope to process the raw EEG into autospectra. This furnished numerical values of the amplitude of EEG activity separated into 17 frequency bands for each of 16 brain areas concomitantly. The specific purpose of this study was to explore group and individual differences that may relate differently to different brain areas, that may relate to amplitude of EEG activity in ~ wide range of frequencies, and that may relate to different conditions of stimulation and their interactions. Conceptualization o f the schi=ophrenic disorder A major difficulty of research in this area lies in the conceptualization of the disorder and the method used for classifying patients. For the purpose of this research the following definition o.f schizophrenia was used: Schizophrenia is a

378

clearly discernible clinical entity which ranges on a continuum from non-psychotic, well compensated schizophrenia to those forms in •which the schizophrenic signs and symptoms are directly observable in behavior. The non-psychotic group of schizophrenics reports: thought disturbance, inability to edit out conflicting trains of thought, half-formed thoughts, autistic instrusions, blocking, and thc.ught insertion. Affect is frequently blunted, ar~,d a feeling of emptiness is often reported. There is a general anhedonia, l~erceptual aberrations are always reported, such as depersonalization, derealization, sudden alterations in body image, people appearing flat and machinelike, loss of depth perception, altered size constancy, etc. A common feature is withdrawal often accompanied by an irrational fear of people. For the psychotic end of the continuum, the eruption of the abnormal thought, affect, or perception into behavior, constitutes an acute schizophrenic psychosis. In this state reality testing is lbr the most part lost. There is behavioral evidence of ambivalence characterized by contradictory thoughts expressed in speech or by hesitancy and indecision in the middle of a motor act having a clear goal. Associations may be loose, and the content of speech may be filled with symbolic references to aggression and/or sex. Predicate logic and "word salad" predominate. Hallucinations, delusions and ideas of reference may be evident. In between the behavioral extremes of the non-psychotic and psychotic forms of schizophrenia is the chronic non-paranoid schizophrenic. These patient: exhibit many of the above dysfunctions in ~aeir behavior, but there is some stabilization of their illness. Adaptations are rife, and some reality testing permits a superficial relating to people in the outside world. The intensity of the psychotic signs, though great enough to be easily observed, is not sufficient enough totally to disorganize the patient. In addition, the psychotic symptoms are quite constant and relatively predictable. Three behaviorally distinct forms of schizophrenia, assumed to be stages in a continuum of a common illness, have been defined. In this study, only non-psychotic, compensated schizo-

D. GIANNITRAPANI AND L. KAYTON

phrenics and chronic non-paranoid schizophrenics were chosen. METHOD

The sample included 10 schizophrenic subjects as defined above and the same number of normal controls, matched for age and sex. Mean age for both groups was 19.6 years; the range was from 16.4 to 25 years with 6 females and 4 males in each group. The schizophrenics, all adolescents or young adults hospitalized at the Institute for Psychosomatic and Psychiatric Research and Training, Michael Reese Medical Center (P&PI), received the following daily medication at the time of testing: Subject Nos. 0, none: 1, none: 2, thioridazinc Hcl 75 mg, trihexyphenidyl Hcl 6 mg, trifluoperazine Hc120 mg; 3. trifluoperazine Hcl 20 rag, imipramine 100 mg; 4, none: 5, chlorpromazine 50 rag: 6, chlorpromazine 100 mg, fluphenazine Hcl l0 rag; 7, large doses of thioridazine Hcl and chiorpromazine; 8, none: 9, none. After remission of the acute psychosis subjects were interviewed by a psychiatrist, if a subject was never acutely psychotic the interview took place shortly after admission. These interviews were tape recorded, and then consensual judgement of a diagnosis was made by two senior psychiatrists. If there was any uncertainty as to diagnosis, the subject was not accepted into this study. The normal group, recruited from among hospital employees and local high-school and college students, was paid for participating. Both groups were administered the EEG according to the Laboratory's standard procedure by which recordings were obtained from 16 unipolar electrodes with reference to both ears. Ten leads were in the temporal line, placed according to the 10-20 system, and there were six equidistant electrodes internal to the temporal line, Throughout the entire session, the 16 channel EEG was recorded on 24" paper. Information from each brain area was digitized at the rate of 128 12-bit conversions/see and recorded on computer tape in a series of eight 8 see records. Subjects were run through the following

379

SCHIZOPHRENIA AND EEG SPECTRAL ANALYSIS

standard sequence of eight conditions, each 48 set: in duration: I. Initial awake resting. 2. Listening to white noise. 3. Listening to music (from Tchaikovsky's "'Marche Minh~ture'" ). 4. Listening to the human voice (reading from Tom Sa,t3"er). 5. Doing mental arithmetic (subtracting serial 7's). 6. Viewing a "-"~ual stimulus la poster of different checked patterns). 7. Eyes open but wearing diffusing genies. 8. Final awake resting. One 8 see record from each condition, free from artifacts, was visually selected for analysis. Data analysis was performed through an adaptation of program BMD × 92 (Massey and Jennrich 1969) which produced autospectra values from ! to 34 c/sec in 17 bands, each 2 c/see wide. Values were obtained for each of the eight conditions from the 16 different brain areas. The method of instrumentation and data analysis employed has been described elsewhere

(Giannitrapani et aL 1971 ). The use of multiplechannel spectral analysis presented the investigators with a degree of interchannel discrepancies which in less complicated procedures had not been considered of consequence. New techniques for normalizing the data became necessary and were d e v e l o ~ (Clusin et aL 1970) to equalize numerically these discrepancies due to differences in the amplifier's response to different frequencies. These differences cannot be equalized by standard calibration procedures. The values for magnitude of autospectra are disproportionately large in the lower frequencies. The autospectra scores were transformed into their root mean squares, then into their log equivalents. These log amplitude scores satisfy the requirements of the analyses of variance performed on the data. Programs for the analysis ofover 1000 columns of data had been developed for previous EEG studies (Sorkin et al. 1964). RESULTS

Four analyses of variance were pert'ormed on

TABLE I /:-tests of Auto Log amplitude data lbr the four analy~es of variance, Frequency groups

d.f.' Groups Conditions Areas Frequencies C ×A CxF AxF C×AxF CxG AxG FxG CxAxG CxFxG AxFxG CxAxFxG Total

I 7 15 3 105 21 45 315 7 !5 3 105 21 45 315

I (2 -10 c'sec)

II 110 18c/see)

(I~ 2 6 c s e c )

Ill

IV 126 3 4 c s e c )

0.01 3.7** 38.7** 50. I ** 4.6** 4.5** 38.0** !.6"* 0.7 2.4** 0.8 1.2 0.7 13.6"* 1.2"*

!.1 ! 3.9** 27.9** 50.9** 4.9** 8.2** 9.6** i.5"* 1.4 2.2** 2.9* 0.9 !.7" 19.7"* 0.8

0.3 6.8** 3.7** 50.4** 2.7** 2.2** 5.2** !.2"* I ._" 1.9* 2.3 0.7 i.8" 16.8"* 0.8

!.i 4. I ** 5.4** 15.3** 2.0** !.0 i. ! !.1 ! ._"~ I. I 6.2** 0.6 1.2 19.3"* 1.1

i 0239

, Groups tested against subjects/groups and all other terms tested against their respective pooled subjects terms not listed in this table. * F-test significant beyond the 0.05 level. ** F-test significant beyond the 0.01 level.

380

D. GIANNITRAPANI AND L. KAYTON

TABLE II Auto Log amplitude means of normais and schizophrenics for different brain areas. Conditions and frequencies are pooled. Frequency groups Brain areas

I (2-10 c/sec) Schiz. Prefrontal Lat. Frontal Frontal Central Temporal Posttemporal Parietal Occipital

Left Right Left Right Left Right Left Right Left Right Left Right Left Right t, efi Right

1.24 !.24 !.08 1.12 1.14 1.14 1.11 i.10 0.96 0.95 1.00 0.98 i.10 1.09 1.05 1.04

Norm. >> 1.18 >> 1.17 1.10 > 1.07 1.14 !.!2 !.!1 !.10 0.99 0.93 1.02 0.96 1.12 1.09 < 1.10 <~ 1.12

11 (10-18 c.sec)

!!! (18-26 csec}

IV {26 -34 c:sec)

Schiz.

Norm.

Schiz.

Norm.

Schiz.

11.79 0.79 0.75 0.71 0.82 0.81 0.84 080 fi.74 0.64 0.:~;5 0.76 0.92 0.87 0.99 1.00

0.e4 ~ 0.6a >> 0.62 >> 0.60 >> 0.61 0.61 0.60 0.59 >> 0.59 0.38 ~ 0.59 0.57 >> 0.61 0.59 0.62 0.61 <

0.58 0.58 0.56 0.52 0.59 0.59 0.58 0.53 0.56 0.47 0.58 0.51 0.63 0.58 0.66 0.66

0.51 0.51 0.46 0.47 0.42 0.42 0.40 0.41 0.38 0.41 0.38 0.40 0.39 0.38 0.41 0.40

0.75 0.75 0.69 0.70 0.75 0.75 0.77 0.76 0.66 0.65 0.74 0.73 0.81 0.80 0.84 0.85

< < ,~ <~ <~ <~ < ,~ ~ <~ <~ ,¢ <~

Norm. >> ~ > >> > > > ,> >> > >>

0.44 0.43 0.40 0.39 0.37 0.36 0.35 0.29 0.40 0.33 0.32 0.28 0.36 0.34 0.38 0.39

l'~it'ference significant beyond 0.05 level; ,:.; = Difference signilicant beyond 0.01 level.

the log amplitude data by separating the data into four frequency ranges: 2-10 c/see, 10-18 c/see, 18-26 c/see, 26-34 e/see. This was necessitated both by limitations in the size of the program and by amplitude differentials at different frequency ranges which were still present in the log amplitude scores. Table I shows that significant differences between conditions which had been previously observed (Giannitrapani 1970, 1971 ) were confirmed. Significant group differences related to brain areas frequencies and their interactions. Group differences were found for conditions only in some of the higher order interactions. Inspection of the means of the areas × groups interactions (Table I I) indicates that in the lowest frequency range the schizophrenics showed greater amounts of activity in the frontal poles than the normais while the normals showed greater activity than the schizophrenics in the occipital poles. These significant differences are primarily due to the activity in the 9 c/sec band (Table III) which shows greater activity among the schizophrenics in most anterior areas. In the 10-18 c/sec range {Table II) all the significant

differences are obtained by the normals having a greater amount of activity than the schizophrenics. These differences are primarily due to the activity in the i I and 13 c/see bands {Fig. 1). In the frequency ranges above i 8 c/see {Table II, Groups III and IV), practically all significant differences indicate that schizophrenics have more activity than normais, and Fig. I shows that these differences are primarily due to the activity in the 19 and 29 c/see bands. 1.50 LOG AMPLITUDE LOG AMPLITUDE 1,00

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Fig. !. Mean log amplitude EEG scores in 16 frequency bands 2 c/see wide for schizophrenics and normal controls, averaged over 8 conditions {for a total of 64 see of EEG)and 16 brain areas.

SCHIZOPHRENIA AND EEG SPECTRAL ANALYSIS

381

TABLE !11 Portion of the Condition × A r e a s x F r e q u e n c i e s x Groups interaction showing the means of the 9 c s e c band for the three conditions showing the greatest diffe'-entiation: Resting. Voice and Arithmetic {Auto Log amplitude means }. Conditions .................................. Resting Voice

Brain areas

Schiz.

Prefrontal

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Frontal

Central

Temporal

Posttemporal

Parietal

Occipital

Norm.

Schiz.

Right

I. 12 I. 13

,> ~>

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I. 17

,>

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I. 13

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,>

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I. 15

I. 15

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1.22 V 1.1 ~

"

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! 1"~

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1.00

t|3}6

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11.94

I.t)l

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4

1,15

1,04

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1,12

>

1.06

Left

1.22

Right

I "~'~

Left

1.21

Righl

!,23

Left

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>

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Norm.

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!.25 1.24

~ >

I.II 1.08

0.98

I. 13

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!.112

0.93

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0.98

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1.13

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1.117

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1,19

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1,13

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1.32

1,15

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1.26

I.I 7

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1.24

1,119

I,IJ6

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1.0~

0.97

!.114 v

< = D i f f e r e n c e significant be~'ond the 0.05 level: ¢~ -:: l)ifference significant be.~ond tile O.l|l lexel.

Focussing on the differences between normals and schizophrenics in narrower frequency bands and pooling all conditions and brain areas, Fig. I shows the mean differences between groups. All of the differences marked with a pointer are significant beyond the 0.01 level, and for the 29 c/see the difference is significant beyond the 0.0000002 level of confidence. To determine the contributions of individual subjects to these differences, individual log amplitude graphs were obtained for each of the 20 subjects and are shown in Fig. 2. The normals are presented separately from the schizophrenics on a displaced scale so that a better comparison of group characteristics can be made. Inspection of Fig. 2 indicates that the schizophrenics are a less homogeneous group in the amplitude of their activity. The figure also

shows lower dominant frequency in the schizophrenics (9 c/see) with some of these subjects having a rather broad peak of alpha activity encompassing both the 9 and 11 c/see bands, i.e., activity all the way from 8 to 12 c/see. Another notable difference is in the 19 c/see band, where the schizophrenics show much greater activity than the normals. The 29 c/see activity presents the most significan ° difference where the normais lack even a vestige of a peak while at least half of the schizophrenics have a high peak in this frequency band. Fig. 3 presents scatter diagrams of the scores of the individual subjects. This is done separately for the 19 and 29 c/see scores as well as for their averages. All three diagrams show that while the normal subjects show a rather homogeneous distribution of this activity, the schizophrenics

382

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Fig. 2. Log amplitude EEG scores in 17 frequency bands 2 c/see wide tbr 10 schizophrenic subjects and 10 normal controls, averaged over 8 conditions (for a total of 64 sec of EEG) and 16 brain areas. The numbers 0--9 on the right side of the graphs lbr the schizophrenics are subject numbers (see Method).

FREQUENCY BAND

0 O* *00.

19

¢r t ,A.,~

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O O*

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AMPLITUDE

Fig. 3. Distribution of log amplitude EEG scores in the 19, 29 and 19 + 29 c/see bands for 10 schizophrenic subjects and 10 normal controls, averaged over 8 conditions (for a total of 64 sec of EEG} and 16 brain areas.

seem to be distributed into three distinct groups. Fig. 4 shows the scores of each pair of homologous brain areas condensed into difference scores. The normal group showed asymmetry of activity in the parietal, lateral, and temporal areas while there was almost no significant difference in the schizophrenic group. This homologous symmetry is not characteristic of individual patients but is the result of averaging the diverse asymmetrical patterns of the schizophrenics. To evaluate whether the asymmetries of the normal group were related to the conditions used in the study, inspection of the distribution of means reveals that most of the significant activity was concentrated in the 9 c/see frequency band. The mean values for selected conditions (Initial Resting, Voice and Arithmetic) in Table III reflect the greater overall amount of 9 c/see activity as well as the lack of left-right differences in the schizophrenic group, both mentioned pr, viously. In the temporal areas the normals show a typical homologous asymmetry with 9 c/see activity greater on the left side. The schizophrenics, however, typically show more right side activity, except in the arithmetic condition where they perform as the normals. DISCUSSION

1. D o m h l a n t a l p h a . l i ' e q u e n o "

While alpha frequency was within normal range for both groups, the experimental subdivision of alpha activity into two frequency bands (8-10 and 10-12 c/see) showed that tile schizophrenic group had the mean of their dominant activity in the lower of the two frequency ranges. It has been demonstrated that with maturation the dominant frequency of the EEG slowly increases (Lindsley 1938). On the basis of alpha frequency development, it would be possible to argue for either an arrested development or a regression in this electrophysiological activity among the schizophrenics, even though this lower frequency of alpha activity is still considered to be within normal limits. This finding had been observed by Gibbs (1939) and Itil et al. (1972), with different techniques and the developmental hypothesis had been invoked by Volavka et al. (1966) to explain the excessive theta found in these patients.

383

SCHIZOPHRENIA AND E E G SPECTRAL ANALYSIS IqiE~TAL

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SCHIZOPHRENIC STUDY HOMOLOGOUS DIFFERENCE SCORES

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of I(~ brain areas, a~,erag,ed o~,~er8 conditions (for a total of 04 s~.n.,of EEG). Conditions show no sigJ)ificant dil'ferenc~:s bcl p.'~:¢n tile two groups. Dots indicate" the I).A)5 level ol'signil'icance,

The scalier in the frequency of alpha activity 2, Domimmt alpha ti'eqteency sctttt(,r Dominant alpha activity for the normal sul~- which occurred in half of the schizophrenic jeers occurs predominantly within a narrow sample could be regarded as a "diffused" alpha 2 c/see band of IO-12 c/see (Fig. 2). Among the biorhythm. The scanning hypothesis of alpha schizophrenics whose alpha activity is not activity (Pills and McCul!och 1947: Walter restricted to the narrow 8-10 c/see band, domi- 1950) can perhaps be related to schizophrenic nant activity occurred in a broader, perhaps behavior. Giannitrapani's (1971) rationale is less stable, frequency range from 8 to 12 c/see. that alpha activity furnishes a rhythm for a The question of whether this scatter is a func- generic search for stimuli which ceases or subtion of less stability of alpha activity among the sides in the presence of a broad range of percepts, schizophrenics brings to mind the findings ob- whether internal or external. It would follow that tained with EEG integrators and summarized by any disturbance or irregularity of this activity Lifshitz and Gradijan (1972). Goldstein and could either produce, or be a correlate of, a Sugerman (1969), for instance, studying the left disturbance or irregularity in the processing of occipital area and 20 sec epochs found in schizo- internal or external percepts, such as that found phrenics a lower **coefficient of variation", i.e., in schizophrenic subjects. a lower amplitude variance of the record. The findings cannot be compared because, in the 3. Dominant acliriO, harmonics The most noticeable difference between the present investigation, record variability was not two groups was in the amount of 19 and 29 studied. Following developmental theory (Werc/see activity. For the normals, the peak in the ner 1940) it is quite possible that among schizophrenics, along with greater rigidity of global 19 c/see band cannot be physically the second amplitude, there is a greater lability or less harmonic of a fundamental in the dominant 11 regulation in the activity within given frequency c/see band (10--12 c/see) while the schizophrenics show peaks of activity that could be harmonic of bands.

384 a fundamental between 9.4 and 10 c/sec. Consideration of this possibility awaits further research as well as development of new theories on the regulation of harmonic activity in the brain. 4. Fast beta activity

Evidence for a greater amount of fast activity in schizophrenics has been available for many years (Gibbs 1939; Kennard et ai. 1955). Since tension had been established as a correlate of fast activity (e.g., Shagass 1954), the excess of fast activity was often interpreted as an indication of tension. Kennard's graphs obtained from an Offner analyzer (Kennard et al. 1955, Fig. 2, C and D), however, indicate that the increase in fast activity is in two broad bands of 16-20 c/sec and 24-27 c/see. Considering the broad-band responsiveness of the early electronic Waltertype resonating filters, these broad-band findings could have been the result of relatively narrowband activity in the 19 and 29 c/see region, ltil et ai. (I 972), with broad-band analog frequency analysis, also found significantly higher amplitude of beta activity above 22 c/see in schizophrenics. The presence of beta activity could be thought. of as due to the intrusion of muscle artifacts into the record. While this might be possible for broad-band beta activity, muscle artit'acts are not known to show peaks in such narrow bands, in brain areas unrelated to muscle groups, and are especially not likely to occur in so many schizophrenic subjects at the same EEG frequency. It has also been observed that broad-band beta activity appears and disappears under different conditions in different brain areas again unrelated to muscle groups (Giannitrapani 1971). The spectre of muscle artifact, therefore, cannot be invoked to account tbr beta activity in light of the recent observations made possible by new methods of processing EEG. The possibility that the 19 and 29 c/see peaks of the schizophrenics in this study are a consequence of psychotropic medication is not plausible in light of the following considerations: (I) The three largest peaks (a peak is defined in relation to a patient's level of activity in immediately lower and higher frequency bands) are obtained in patients Nos. ~, i and 4 who are not on any medications. (2) For the patients showing

D. G I A N N I T R A P A N I A N D L. KAY'ION

the 29 c/sec peak, medications are phenothiazines which are known to decrease beta activity except in some cases of low level doses (Akpinar et al. 1972; ltil el aL 1972). The only question is for patient No. 3 who is also on imipramine, a drug known to increase beta activity (Itil 1968: Fink 1965). (3) Unlike the case for barbiturates there is no evidence that increase of beta activity consequent to psychotropic medication occurs in a narrow-band less than 2 c/see wide as in the case of the 29 c/sec peak in the present experiment. The evidence available supports the presence of a broad-band effect (Itil et al. 1971) consequent to psychotropic medication.. The production of narrow-band fast activity has been observed repeatedly following administration of barbiturates. Shagass (! 956) demonstrated that changes in amplitude of fast activity produced by sodium-amobarbital could be used as an index of the rate of depressant action of the drug on brkdn activity. This work was done by analyzing amplitude of fast activity either by hand or with a broad-band Davis integrator. The increase of narrow-band fast activity consequent to barbiturate medication and the presence of narrow-band fast activity among schizophrenics suggest the possibility that both effects might be a correlate of impaired alertness, Both these effects are not to be confused with the increase of fast activity which occurs with increase in mental activity. The latter phenomenon is a broad-band effect observable in all bands from 18 to 34 c/see (Giannitrapani 1970). These findi,ig are in accord with the observation of Mundy-Castle (1957), who described beta activity as being of two types, one harmonically related to alpha and the other possibly related to mediation of information within the brain. Distinction between the two has been difficult because of the availability of only broad-band analog filtering in the past, which would distribute narrow-band activity over a broad range of frequencies. Because of the exploratory nature of the investigation the reader should be cautioned that the findings are tentative and that the theoretical relationships are only suggested. They are presented here in the hope of stimulating further research in this area of EEG frequency analysis and psychopathology.

SCHIZOPHRENIA AND EEG SPECTRAL ANALYSIS SUMMARY

Relationships between EEG features and schizophrenia were studied via digital spectral analysis. Ten hospitalized adolescents or young adult schizophrenics in remission from an acute psychotic episode and ten normal controls matched for sex and age underwent an EEG examination obtained from 16 unipolar electrodes in eight stimulus conditions. All channels were digitized in 8 sec samples, and Fourier spectra were computed for frequencies from 0 to M c/see in 17 bands, each 2 c/see wide. Four analyses of variance were performed on log-amplitude scores to obtain significance for the following findings: I. The distribution throughout the brain of the 9 c/see band activity is more uniform for the schizophrenics than for the normals. 2. The peak of dominant alpha frequency occurs at I I c/see for the normals and at 9 c/see for the schizophrenics. 3. Dominant alpha frequency scatter is greater for the schizophrenics tbr whom broad-band peaks of dominant activity al~ likely to occur. 4. Peaks at higher frequencies accrue at the 19 c/see band, significantly higher for the schizophrenics, and at the 29 e/see band tbr half the schizophrenics and none of the controls, it is proposed that these possible harmonics of dominant activity in the schizophrenics are a correlate of impaired alertness. The findings indicate that EEG autospectra show correlates to a portion of the patients having the primary diagnosis of schizophrenia in this study. Even though these findings await confirmation, the manner in which the scores in the 19 and 29 c/sec bands are distributed for the schizophrenics points to the possibility that spectral analysis of the EEG could ultimately prove useful in differentiating between the disorders which are currently subsumed under the general heading of schizophrenia.

3,85

ou jeunes adultes hospitalis6s, en p6riode de r6mission d'un 6pisode psychotique aigu et 10 sujets normaux appari6s quant aux sexe et ",i r~ge ont subi un examen EEG obtenu sur 16 61ectrodes monopolaires dans 8 conditions de stimulation. Toutes les chaines ont 6t6 digitalis6es par 6chantiUons de 8 sec, et le spectre de Fourier a 6t6 caicul6 pour les fr6quences allant de 0 ",i 34 c/sec en 17 bandes de 2 c/sec chacune. Quatre analyses de variance ont 6te r6alis6es sur des mesures de log-ampiitude pour aboutir aux donn6es suivantes significatives" I. La distribution sur l'ensemble du ¢erveau de la bande d'activit6 de 9 c/sec est plus uniforme chez les schizophr6nes que chez les normaux. 2. Le pic de la fr6quence alpha dominante se produit "/i I I c/sec chez les nomaaux et 'fi 9 c/sec chez les schizophr6nes. 3. La dispersion de la fr6quence alpha dominante est plus grande chez les schizophr~nes chez iesquels des pies '~ large bande d'activit~ dominante peuvent survenir. 4. Le pic de la fr6quence plus 6levee surviennent/t la bande de 19 c/see, de fa¢on significativement plus grande chez les schizophr/mes, et fl la bande de 29 c/see chez la moiti~ des schizo. phr~nes et chez aucun des contr61es. Los auteurs supposent que ces harmoniques possibles de I'activit~ dominante observ~es chez los schizo. phr~nes soient un corr61atif d'un ~tat de veille perturbS. Ces donn6es indiquent que les auto-spectres EEG montrent des corr61ations a':'ec une pattie des malades de cette 6tude dont le diagnostic primaire est celui de schizophr~nie. Bien que ces donn6es n6cessitent une confirmation, la manitre dans laqueile los mesures se distribuent dans les bandes de 19 et 29 c/see chez les schizophr~nes souligne la possibilit6 que ranalyse spectrale de I'EEG puisse ult6rieurement se r6v61er utile pour effectuer une differentiation parmi les d/~sordres qui sont le plus souvent r~unis sous le titre g6n~ral de schiz3phr~nie. u¢

RESUME ANALYSE SPECTRALE DE L'EEG ET SCHIZOPHRENIE

Los relations entre donn6es EEG et schizophr6nie ont 6t~ 6tudi~es au moyen de l'analyse spectrale digitale. 10 schizophr~nes adolescents

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