The 2nd Department of Physiology, Nagasaki University School of Medicine, Nagasaki, Japan. On the Flash Light Response Activities in the Visual Cortex of Unanesthetized Cats

Acta med. nagasaki. 9 : 186-199

On the Flash Light Response Activities in the Visual Cortex of Unanesthetized Cats

Noriyoshi HIROTA*

The 2nd Department of Physiology, Nagasaki University School of Medicine, Nagasaki, Japan.

Received for publication, March 5, 1965

Single and rhythmic flash light average responses in the visual cortex (lateral gyrus) of immobilized cats by administration of Flaxedil were observed in their time- (Fig. 2C & 3), spatio-temporal- (Fig. 4) and fre- quency-patterns (Fig. 5B & C).

Four positive negative diphasic average deflections were capable of tracing from a variety of portions in the lateral gyrus, each of which was able to designate, for convenience sake, P1, N1, P2, N2, P3, N3, P4 and N4 respectively (Fig. 3) . Their average peak latencies were 21.6, 45.0, 63.4, 78.5, 106.9, 117.3, 154.9 and 178.3 msec respectively, so that P1 and N1 responses were the well-known primary responses. The most conspicuous responses were evoked from the mid lateral gyrus, wherein the early components P1, N1 and P2 due to contralateral stimulus were larger than those evoked by ipsilateral one, but N2 was ipsilaterally dominant. Later components of ipsi- and contralateral responses than N2 were not the same each other in their patterns. Though binocular responses were more prominent than both of ipsi- and contralateral monocular ones, occlusive binocular interaction was revealed in the positive components P1, P2 and P3, whereas facilitatory interaction in the negative components N1, N2 and N3. It was verified in the spatio-temporal average response patterns that primary positive Pi response was unable to observe in the anterior lateral gyrus, but the secondary positive P2 response, which was distinctly and ipsilaterally dominant, was suggested to be an irradiation of P2 in the mid lateral gyrus, in addition, that negative components, N1, N2 and N3 were augmented by binocular stimulation irradiating beyond the extent of responses due to the monocular stimuli to both of anterior and posterior

directions.

This research has been made possible through the support and sponsorship (DA-92-557-FEC-37212) of the U. S. Department of Army, Far East Research Office.

*広 田典 祥

1964 CORTICAL FLASH RESPONSES TN UNANESTHETIZED CATS 187 Though, many reports have published on the evoked cerebral potentials of cat elicited by a flash light stimulus, they contributed chiefly to individualization of primary response components with shorter

latencies, whereas few have been elucidated the late responses3, 4, 8, 32) . Recently, it was demonstrated by SATO16,17,18,19, 17,18,19,20,21,22) SATO et al .27,28) MIMURAI3) , OZAKI et al. 14), TERAMOTO30) , KITAJIMA12) that the average response time-patterns, i. e. crosscorrelograms of the stimulation and masspotential of various brain sites, and their frequency-patterns (frequency spectra) have an equivalent or broader physiological signifi- cance to the excitability cycle of the brain site neighbouring the lead electrode(s). Therefore, observations on the average masspotential responses elicited by mono- and binocular flash light stimuli in the posterior sigmoid gyrus and various portions in the lateral gyrus of unanesthetized cat were performed to elucidate the time-, spatio- temporal- and frequency-patterns of the primary and late responses in

relation to binocular interaction.

METHODS

Under ether anesthesia, adult cats weighing 2.5-4 kg were mounted on the Johnson type stereotaxic instrument after a tracheal canula was fixed for artificial respiration, then the scalp was opened minimal necessarily to place the silver ball tipped monopolar electrodes on the dura or pia covering the posterior sigmoid and lateral gyri. Reference silver wire electrode was inserted into neck muscle of the animal in a dim-lit electromagneticaly shielded room. After the scalp was opened, artificial respiration with oxygen to blow away ether was carried out throughout the experiment and Flaxedil was administrated to immobilize the unanesthetized animal in a rate of 15 mg/kg per an hour through a continuous injector (KN, Natsume Seisakusho), so that fluctuations in the animal conditions were capable of avoiding.

Single or repetitive flash light stimulations were delivered by the photic stimulator (PS-101, San 'ei-Sokki Co.). The flash emitted from the strobo flash valve (FT-100, Mazda) was of about 6000°K daylight, 1 Watt per second energy and about 100psec duration. In front of the flash valve, a frosted glass plate, a shutter with a round iris and a cotton white curtain were placed, through which the beam of the flash light was diffused. The both pupils of the cat were dilated by atropine and placed at the distance of 62 cm from the surface of the strobo flash valve. One of the eyes was covered carefully by a piece of dick and black woolen cloth when a monocular stimulation was delivered.

The intensity of the flash stimulus was delivered through an iris

of 50, 100 or 150 mm diameters. Relative intensity of them in logarithmic

188 _!M; HIROTA Vol. ,9.

Fig. 1. Block diagram of the brain masspotential recording and their bio-infor- mation processings.

scale were 2.1, 2.6 and 2.8 db respectively if the intensity through the iris of 5 mm diameter was taken as 0 db. The bio-information process- ings in our laboratory for obtaining the average response 'time-patterns and their frequency-patterns are illustrated in Fig. 1. Masspotentials (EEGs and evoked potentials) and stimulation signal were recorded on magnetic tapes through 8-channel polygraph (RM-150, Nihon-Kohden Co.) and 8-channel data recorder (SPRA-48, Shiroyamadenshi Co. ) monitoring by ink records through the polygraph. The average response time-patterns were obtained by a simplified method (Sato et al. 196123',

196224') from ink records, through the Pulse Signal Multipurpose Correlator (UCA-26, Sony Co. )26) or the Digital Computer For Data Processing (ATAC-401, Nihon Kohden Co.) from magnetic tape records.

The frequency spectra of these average response . time-patterns were

recorded by the Instant Short Range Spectrum Analyser (ESA-2, Sony

Co)33'. Not only the average responses in a variety of portions of the

posterior sigmoid and lateral gyri respectively, but spatio-temporal

response patterns15) were obtained to map equipotential lines on such a

plane that the post stimulation time and the above various portions

were taken as abscissa and ordinate respectively were also obtained,

Fig. 2. Ink records of brain masspotentials with stimulation signal and average responses obtained by ATAC.

A : control record without flash light stimulation. B : an example of records during-2 per sec flashlight stimulation through an iris with its diameter of 100 mm (relative intensity 2.6 db). C : average response time-patterns obtained by 30 summations. PS : posterior sigmoid gyrus. GL : lateral geniculate body.

CM : N.centre median. L : lateral gyrus. Sig signal of the stimulation. I-EYE, r-EYE & l.r-EYE :

left (contra), right (ipsilateral) monocular and binocular. stimulations respectively.

190 N. HIROTA Vol. 9.

RESULTS

1. Temporal patterns of the average responses in the posterior sigmoid and lateral gyri.

By delivering the flash light stimulus at an interval of about 500, 350 or 100 msec, not only the well-known primary positive negative diphasic response with lesser peak latency than 50 msec in average but the late responses with longer peak latencies were capable of obtaining by applying ATAC, UCA and/or the simplified average response analysis23, 24) Two examples traced by ATAC and UCA were illustrated in Fig. 2 C and Fig. 5 A respectively. In the former four positive (downward) and negative (upward) deflections were able to recognize most distinctly at the mid lateral gyrus (Lead L3), around which the primary visual area will be located. In the latter, three or two positive and negative ones were observed distinctly in the visual

Fig. 3. Combined records of the average response time-patterns.

A : responses elicited by contralateral (left) (hatched lines connecting white

circles) and ipsilateral (right) monocular (solid lines connecting black circles) flash

light stimulus delivered at the time origin (arrows pointing upward). B : response

due to the binocular stimulus (solid lines) and algebraic summations of ipsi- and

Gontralateral responses (hatched lines connecting crosses "+").

1064 CORTICAL FLASH RESPONSES IN t7NANE5THETIZED CATS 191 cortex (Fig. 5 A, Lead 2, 3, 1 and 4), since the rhythmic flash stimuli were delivered in this instance at the interval of 100 msec. The portion of maximum response was located more posterior than the former example. This difference may be caused by the higher frequency and weaker strength of the stimulation. The first, second, third and fourth positive deflections were designated, for convenience sake, P1, P2, P3 and P4 respectively, and those of the negative ones nominated for N1, N2, N3 and N4 respectively (see Fig. 3). Their average peak latencies in five experiments are indicated in Table 1.

Table 1.

Peak latency of average responses in the visual cortex

No. Pi

40.0 60.0 123.0

--- --- - --- --- -- --- --- - --- - --- --- -- --- - ---

Average

CatN1 P2 N2 P3 N3 P4 N4

msec msec msec msec msec msec msec msec

#

41 24.6 41.4 63.1 81.1 100.2 117.3 145.8 178.3

#

35 18.7 51.1 64.0 77.8 94.0 - - -

#

37 29.0 54.4 66.6 80,0 110.5 - - -

#

58 20.0 38.0 75.0 - -

#

58 23.0- 163.0 -

21.6 45.0 63.4 78.5 106.9 117.3 154.9 178.3

Here the flash light stimulation of 10 and 7.7 per sec were delivered respectively to the cat # 35 and # 37, so that N3 and more late responses were unable to recognize. It would be obvious from the results in Table 1 that the responses P1 and N1 are the well-known primary diphasic response and other responses would be the late secondary ones.

Though the primary positive response P1 with its peak latency of 20 -30 msec was not brought out in response to ipsi-, contralateral mono- cular and binocular stimuli at the anterior portion of the mid lateral gyrus (Lead L4) and the posterior sigmoid gyrus (Lead PS) (see Fig.

2 C), more late positive and/or negative responses were exhibited. This evidence in the anterior portion of the mid lateral gyrus would suggest one of the properties in the secondary visual area32) .

2. Average response elicited by mono- and binocular flash light stimulus.

The average response curves brought out by ipsi- and contra- lateral monocular flash stimuli in Fig. 2 C were combined to compare

easier the both responses, as illustrated in Fig. 3 A. It was revealed

in this combined records that the P1, N1 and N2 responses at the mid

Fig. 4. Spatio-temporal average responses mapped out equipotential lines.

A : contralateral (left) monocular stimulus. B : ipsilateral (right) monocular stimulus. C : binocular

stimulus. Solid lines : positive potential. Dotted lines : negative potential. Hatched lines : zero poten-

tial. Relative value of each epuipotential line is indicated by numerals.

1964 CORTICAL FLASH RESPONSES IN UNANESTHETIZED CATS 193 lateral gyrus (L3) were elicited more prominently by the contralateral (left) monocular stimulus than those by the ipsilateral (right) monocular one, whereas more late N2. P3 and P4 responses due to the ipsilateral stimulus were more enhanced. Similar tendency on the P1, N1 and P2 responses was also observed in the posterior portion of the lateral gyrus (Lead L2).

It was found by comparing the average response elicited by bino- cular stimulus at the mid lateral gyrus (L3) with those of the algebraic summation of the average response due to ipsi-. and contralateral monocular stimuli (Fig. 3 B) that the positive responses . P1, P2 and P3 were smaller than those of the latter, whereas negative responses N1, N2 and N3 in the former were higher than those of the latter.

Therefore, occlusive and facilitatory binocular interactions were sug- gested respectively in the positive and negative responses at the cerebral primary visual area. However, the responses P1, N1 and' P2 due to binocular stimulus at the posterior mid lateral gyrus were the same as those of algebraic summations. Hence, no binocular interaction was observed at this portion. More late responses N2, P3 and N3 at this portion were, on the contrary, the same binocular interactions as those at the mid lateral gyrus (L3) were observed. In the dorso-lateral gyrus (Lead L1), the primary P1. and N1 responses due to binocular stimulus were the same in their amplitudes of the algebraic summation to

suggest no binocular interaction, whereas P2 and N2 responses of the former were more prominent than the latter to suggest facilitatory binocular interaction.

3. Spatio-temporal response patterns.

The spatio-temporal response patterns mapped out equipotential lines of the average. response, which were derived from the data in Fig. 2'C and Fig. 3, are illustrated in Fig. 4. The time origin of the abscissa is the time point of the flash light stimulus delivery.

It was verified in Fig. 4 that the primary responses P1 and N1 were elicited more prominent by the contralateral monocular flash light stimulus than the ipsilateral one around the mid -lateral gyrus (L3), and the second positive response P2 was also the same. On the contrary, the late response N2 elicited by the ipsilateral stimulus was rather more considerable. In addition, the second surface positive response P2 was induced , by the same stimulus relatively higher in the anterior portion of the lateral gyrus (L3) and the posterior sigmoid gyrus (PS).

It was also verified that the binocular flash stimulus drived not only

more regular and remarkable evoked potential of the primary (P1, N1)

and more late responses (P2, N2, P3, N3, P4 and N4). They extended

to both of anterior and posterior directions to indicate the irradiation of

Fig. 5. Crosscorrelograms of flash light stimulation and masspotentials and their frequency spectra.

A : crosscorrelograms of 10 per sec flash light stimulation and masspotentials in a variety of somato-

sensory and visual cortex. B : frequency spectra of the crosscorrelograms. C : peak heights of the

response in the frequency spectra in relation to the locations of leading electrodes. 1, r and 1 • r :

response peak heights due to left (contra-), , right (ipsilateral) and binocular` stimulations. 1 + r :

summations of peak heights due to both monocular stimulations. White circles in the bottom are the

summation of the peak at the stimulating frequency only. At each location , peak of the (first) high

harmonic frequency was placed on the head of the peak at the stimulating frequency.

1964, CORTICAL FLASH RESPONSES IN UNANFSTHETIZED CATS 195 the masspotential activities due to binocular visual afferent inflows in the cerebral visual area. And the binocular surface positive P2 response extended beyond the cerebral visual area to the posterior sigmoid gyrus.

4. Average response frequency. Patterns.

When the stimulation to evoke masspotential is delivered rhythmi- cally, wave like evoked potentials of the stimulating frequency and/or

its high harmonic frequency are driven, as illustrated an example in Fig. 5 A and B. In the frequency spectra of the rhythmic average response, average intensities of the response activities are indicated by the height of the peak at the stimulating frequency and its high har- monic frequency. Summation of these peak heights, therefore, express the total activity"' evoked by the rhythmic. stimulation. When the response activities at a variety of the portions in. the lateral gyrus and posterior sigmoid gyrus were arranged in spatial order, two groups of response activities were revealed, one was in the visual area (Lead 1, 2, 3 and 4) and other one was in the somatosenory area (Lead 6 and 7).

DISCUSSION

FORBES and MORISON (1939)10) studied on the cerebral evoked poten-

tial with long latency brought out by a stimulus to sciatic nerve of cat

under deep barbital anesthesia and discriminated from the primary

response to designate the "secondary response". Thereafter, many

investigators have tried to individualize wave components in the evoked

potentials of short latencies due to visual stimulation or stimulation to

the optic pathway and few have been elucidated the late responses3,4,

8,10, 32) , on which there are some discrepancies in their opinions. TORES

and WARNER (1962)32'described two types of the late responses desig-

nated Type I and II in unanesthetized and immobilized cat with Flaxedil,

i. e. the late response preceded by, the primary response (Type I) and

that without preceding the primary response (Type II). And they report-

ed the primary response was exhibited with its latency of 25.6 msec

and the late response of Type I and II were elicited with their latencies

of 58.4 and 79.2 msec respectively. However, they did not analyse

precisely the wave form of these evoked potentials, since they observed

the potentials by superimposition of 10 - 15 sweeps of the cathode ray

oscilloscope. On the contrary, average response time-pattern derived

from the summstion of the masspotential under the basic principle of

the average response analysis (SATO et al. 196128', 196224), SATO 196422))

by means of the digital computer (ATAC 401) or the pulse signal

multipurpose correlator (UCA-26) traced a regular wave form composed

of four pairs of positive and negative diphasic deflections, which were

able to designate P1, N1, P2, N2, P3, N3, P4 and N4 respectively. They

196 N. HIROTA Vol. 9.

were most prominent by contra-, ipsilateral monocular and binocular flash light stimulations in the mid lateral gyrus (Fig. 2C, Lead L3).

This evidence coincided with the results obtained by DOTY (1958)9).

Here, P1 and N, are the well-known primary response and P2 and N2 yielded in the primary visual area, which will be located around the positions of the lead electrodes L3, L2 and L1 in Fig. 2 C, coincided with the type I late response by TORRES and WARNER , whereas those elicited in the anterior portion of the mid lateral gyrus (Fig. 2C, L4) will be corresponded to the Type II response, since P2 and N2 responses

at this portion did not preceded by P1 and N1 responses. However, it was revealed by obtaining the spatio-temporal average response pattern that these Type II late responses were spatial extention of P2 and N2 followed by the primary response elicited in the primary visual area

(mid lateral gyrus L3).BUSER and BORENSTEIN (1957)8) reported that the secondary association responses localized to the surface of the association cortex seemed to occur independently from those of the primary pro- jection cortex. These responses would also be corresponded to the P2 and N2 responses in the anterior mid lateral gyrus (Lead L4), which was verified an extension of those in the mid lateral gyrus. Though BRAZIER

(1963)5' demonstrated such a temporal variety of the late responses in the specific visual projection cortex of unanesthetized cat that they began to fail on stimulus repetition, different patterns of the late response in various portions in the visual cortex (L1, L2 and L3 in Fig. 2 C) revealed their spatial variety.

As already BURNS (1960)7), AUERBAGH (1961)1), etc. demonstrated, the

average responses elicited by the binocular stimulation were larger than

those by contra- and ipsilateral monocular stimulations. Though the

primary (P1 and N1) and relatively fast response P2 were elicited larger

by contralateral monocular stimulation than those by ipsilateral one, as

hitherto pointed out (BURNS7) , AUERBACH1), etc.), the reverse was the

case of N2 response. However, it was suggested in the evidences in

Fig. 5 B and C that the above contralateral dominant activity will not

always the case. There seemed to be some contradiction to the report

that 33 % of the optic nerve fibers were uncrossed and the rest were

crossed 21 and more cerebral neurons were discharged by contralateral

stimulus 7,11). However, there are such possibilities that all optic fibers

would be not necessarily contribute to enhance the masspotential re-

sponse and this response is not necessarily to keep pace with unit

discharges. Though AUERBACH1) demonstrated that the primary response

due to binocular stimulus is the same in its magnitude as the algebraic

summation of those elicited by crossed and uncrossed ; responses, the

binocular P1, P2 and P3 responses in the mid lateral gyrus (Fig. 3B,

L3) were lower than the respective algebraic summations, i. e. occlusive

binocular interaction was observed, wheres the binocular responses N1,

1964 CORTICAL FLASH RESPONSES IN UNANESTHETIZED CATS 197 N2 and N3 were facilitatory binocular interaction. Interactions in the average masspotential responses have already demonstrated by paired stimulation of the flash light and cutaneous electric shock stimulations (TERAMOTO 196430)), by those of the flash light and click stimulations (BRAZIER 19616)) and even some such evidences were demonstrated by SATO et al. 195725), 196027) , 196128), SATO 196421), SONODA29), KITAJIMA12) that alpha blocking phenomenon in the spontaneous EEG caused by a rhythmic flash stimulation is capable of considering as the interaction of the flash and natural afferent inflows to induce spontaneous alpha wave. In addition, interactions in the unit discharges of visual cortex were also reported (BURNS7), HUBEL11), etc.). These interactions including binocular ones will have important unknown physiological significances for man and animal life.

ACKNOWLEDGMENT

The author wishes to express his cordial thanks to Prof. KENSUKE SATO for his kind guidance, encouragement and help for preparing this manu-

script. Thanks are due also to the staffs of the 2nd Dept. of Physiology.

REFERENCES

1) AUERBACH, E., BELLER, A. J., HENKES, H. E. and GOLDHABER, G. : Electric potentials of retina and cortex of cats evoked by monocular and bino-

cular photic stimulation. Vision Res., 1 : 166 (1961).

2) BISHOP, P. 0., BURKE, W., DAVIS, R. and HAYHOW, W. R. : Binocular interaction in the lateral geniculate nucleus. A general review. Transection

of the Ophthalmological Society of Australia, 18 : 15 (1958).

-3) BRAZIER

, M.A.B. : A study of the late response to flash in the cortex of the cat. Acta physiol. Pharm. Neerl., 6 :692 (1957).

4) BRAZIER, M. A. B. : Studies of evoked responses by flash in man and cat.

Reticular Formation of the Brain. (Jasper, Proctor, Knighton, Noshay

and Costello, Editors) Little, Brown and Co., Boston, 151 (1958).

5) Brazier, M. A. B: : Responses in non-specific systems as studied by averaging techniques. Brain Mechanisms. (Moruzzi, Fessard and Jasper,

Editors) Progress in Brain Research. 1 : 347 (1963).

6) BRAZIER, M. A. B., KIELAM, K. F. and HANCE, A. J. : The reactivity of the nervous system in the light of the past history of the organism.

Sensory Communication (Rosenblith, Editor) 'The M. I. T. Press. p.

699 (1961).

7) BURNS, D., HERON, W. and GRAFSTEIN, B. : Responses of cerebral cortex to diffuse monocular and binocular stimulation. Amer. J. Physiol., 198

200 (1960).

8) BUSER, P. et BORENSTEIN, P. : R6ponses corticales "secondaires" a la stimulation sensorielle chez le chat curaris6 non anesthesia. Electro-

enceph. clip. Neurophysiol., Suppl., 6 : 89 (1957).

9) Doty, R. W. : - Potentials evoked in cat Cerebral cortex by diffuse and by punktiform photic stimuli. J. Neurophysiol., 21 : 435 (1958).

10) FORBES, A. and MORISON, B. R. : Cortical response to sensory stimulation under deep barbiturate narcosis. J. Neurophysiol., 2 : 112 (1939).

11) HUBEL, D. H. and WIESEL, T. N. : Receptive fields, binocular interaction

198 N. HIROTA Vol. 9.

and functional architecture in the cat's visual cortex. J. Physiol., 160:

106 (1962).

12) KITAJIMA, K. : On the influence of flicker intensity upon the EEG response. Brain Nerve, 16 : 923 (1964) (Japanese).

13) MIMURA, K. : .On the frequency characteristics of the occipital EEG activities. Brain Nerve, 10 : 397 (1958) (Japanese).

14) . OZAKI, T . , SATO, K . , MIMURA, K . , HONDA, N . , MASUYA, S. and YAMAMOTO, Y. : On the average time- and frequency-pattern of photic flicker

response in relation to intrinsic alpha activiy, verified by a new simple

method. Acta med. Nagasaki., 6 : 83 (1962).

15) RkMOND, A. : Integrated and topological analysis of the EEG. Electro- enceph. clip. Neurophysiol., Suppl., 20 : 64 (1961).

16) SATO, K. : Studies on the statistical analysis of cerebral activities through electroencephalogram. J. Jap. Assoc. Auto. Cont. Eng., 5 : 10

(1961) (Japanese).

17) SATO, K. : On the statistical servosystem and the brain activity. J.

Jap. Assoc. Auto. Cont. Eng., 6 : 321 (1962) (Japanese).

18) SATO, K. On the physiological significance of the EEG analysis. Brain Nerve, 15 : 342 (1963) (Japanese).

19) SATO, K. : On the linear model of the brain activity in electroencephalo-

graphic potential. Folia Psych. Neurol. Jap., 17 : 156 (1963).

20) SATO, K. : On the role of thalamic nuclei and reticular formation upon the generation of the electroencephalogram and myotonogram. I (1963)

and II (1964), Nagasaki.

21) SATO, K. : On the servomechanic analysis of masspotential activities in the brain. Tap. J. med. Electron. Biol. Eng., 2 : 111 (1964) (Japanese).

22) SATO, K. : Bio-information Processing. (1964) Nagasaki.

23) SATO, K . , HONDA, N . , OZAKI, T., MIMURA, K . , MASUYA, S., AWAZU, T., TERAMOTO, S. and KITAJIMA, K. : A new simplified method of correla-

tion analysis of EEG. The Proc. X. Ann. Meet. Japan EEG Soc., 99 (1961).

24) SATO, K., HONDA, N . , MIMURA, K., OZAKI, T., TERAMOTO, S. and KITAJIMA,

K. : A simplified method for determining the average response time

pattern of the evoked potential in electroencephalography. Electroenceph.

clin. Neurophysiol., 14 : 764 (1962).

25) SATO, K., MIMURA, K., OZAKI, T., YAMAMOTO, Y., MASUYA, S. and HONDA, N. : On the "transforming action" of the brain shown in the brain

wave. Tap. J. Physiol., 7 : 181 (1957).

26) SATO, K., MIMURA, K., HONDA, N., TERAMOTO, S. and KITAJIMA, K.

Magnetic correlators in medicine. Medical Apparatus Culture, 3 : 607 (1962)

(Japanese).

27) SATO, K., OZAKI, T., MIMURA, K., MASUYA, S. and HONDA, N. : On the physiology of the brain wave. Clin. Encephal., 2 : 9 (1960) (Japanese).

28) SATO, K., OZAKI, T., MIMURA, K., MASUYA, S., HONDA, N., NISHIKAWA, T.

and SoNODA, T. : On the physiological significance of the average time

and frequency-patterns of the electroencephalogram. Electroe.ceph. clin.

Neuroph ysiol. 13 : 208 (1961).

29) SONODA, T. : On the EEG response to photic flicker stimulation. Psy- chiat.Neurol. Jap., 62 : 925 (1960) (Japanese).

30) TERAMOTO, S. : On the EEG activities of cerebral sensory area and thalamus in cats. Brain Nerve, 16 : 129 (1964) (Japanese).

31) THOMPSON, R. F., JOHNSON, R. H. and HOOPES, J. J. : Organization of auditory, somatic sensory, and visual projection to association fields

of cerebral cortex in the cat. J. Neurophysiol., 26 : 343 (1963).

32) TORRES, F. and WARNER, J. S. : Some characteristics of delayed re-

sponses to photic stimuli in the cat. Electroenceph, chin. Neurophysiol.,

1964 CORTICAL FLASH RESPONSES IN UNANESTHETIZED. CATS 199 14 : 654 (1962).

33) UEMURA, S. : Instant frequeney spectrum analyser of EEG. Data of the research comittee in medical electronics communication society.

(1960) (Japanese),