THE DETERMINATION OF LOCALIZATIONS WITH …existing in the muscles and glands, and can be conducted...

ACTA NEUROBIOLOGIAE EXPERIMENTALIS

SUPPLEMENTUM 3

A CLASSIC IN THE HISTORY OF ELECTROENCEPHALOGRAPHY

English edition of the Doctoral Thesis of

Adolf BECK

THE DETERMINATION OF LOCALIZATIONS IN THE BRAIN AND SPINAL CORD

WITH THE AID OF ELECTRICAL PHENOMENA

with an appendix by

Jadwiga BECK ZAKRZEWSKA

WARSZAWA 1073

P O L I S H S C I E N T I F I C P U B L I S H E R S

Translated from the Polish by

W. A. BINEK and J. S. BARLOW

Editor

Mary A. B. BRAZIER

Polish original

Beck, A. 1891. Oznaczenie lokalizacji w m6zgu i rdzeniu za pomocq zjawisk elektrycznych

Rozpr. Akad. Um. Wydz. Mat.-Przyr. Ser. 11, 1: 187-232

THE DETERMINATION OF LOCALIZATIONS IN THE BRAIN AND SPINAL CORD

WITH THE AID OF ELECTRICAL PHENOMENA

BY

Dr. Adolf BECK

Assistant at the Institute of Physiology, a t the Jagiellonian University in Krakow, Poland

For determination of the site of the nervous centers which control certain functions, two methods are available to the investigaitor: the method of stimulation, and the so-called method of extirpation. In the first method, we stimmulate resltricted areas of the central nervous system with the aid of an electric current or a chemical substance and observe which organs (muscles, glands) become activa.ted. This meth~od of investigation is not precise, because it is extremely difficult to limit the stimulation to a single site; the investigator is unable Im prevent spread of the current with the resulting stimulation of nerve fibers passing beneath the stimulated part and which originate from other parts of the nervous system; he also cannot localize chemical stimulation to a single point. Moreover, with this methlod it is not possible to determine the site of the centers lof the afferent nerves, that is to say, the sensory centers, for obvious reaslons.

The second method, which nature gave us long ago, but which we have learned quite recently, since it has only just been applied for the first time on animals by Ferrier (1870), Fritsch and Hitzig (1870) and especially Mu& (1876), is based m removal of certain regions of the central nervous system, and on observation of the changes in the functions of certain organs resulting from the removal; these changes result from lack of fundions of certain organs and are therefore generally termed fall-out functions. With this method it has already been possible .to investigate in detail the xnotor spheres in animals, and less exactly the sensory spheres. In man, however, this would be almost the only method

8 A. BECK

afforded us by nature, resulting in hfferent losses of the brain substance, with consequent loss of functions; Here we can determine with equal accuracy the changes in the functions of motion, secretion, sensation, and in psychical functions.

Both merth~ods have the feature in common that they arrive a t the determination of localization from the center to the periphery; that is, having selected a certain region, for instance, on 'the cortex, as the abject of study, the organ is mught which is supplied with nerves fram that region. These two metholds, which could be termed centrifugal, correspond to two others, which could collectively be called centripetal. In the latter, a particular organ at the periphery is selected, and a search made Em centers to which the sensory nerves of the organ proceed, or rather, the centers which supply the nerves #of motion or secretion to the organ. This aim can be achieved in two ways: one can either destroy a certain organ and after a certain time demonstrate the abophy of that part of the central nervous system the centers of which directed the organ, or, stimulating certain regions, for example, of the eye, ear, or skin, demonstrate that the centers reached by the nerves from those regions become activated. In this respect also, there is a precedent from nature. In 1875 Sander 2 described a post mortem on a 15-year-old boy, who when he was three years old suffered from infantile paralysis (poliomyelitis) and was paralyzed in all the extremities until the end of his life. The post mmortem showed atrophy, or rather underdevelopment, of the psych* motor pads of the cortex. Since the paralysis in this case was not caused by changes in the brain but followed an abnormality of the cord, one has consider the atrophy of the brain as secondary, caused by inactivity.

It would be easy to imitate those pathdlogkal changes. One could amputate a leg of a newborn animal, or destroy the eye, the ear, etc., and examine its cord and brain after a long interval of time. Such an examination shoultd be thorough and should not be limited to ascertaining of atrophy macroscopically, as was done by Sander, but the 'brain should also be examined under the microslcope. Apparently such investigations already exist, and were carried out by Sikorski and Bechterev; however, desyite a careful search in the literature, I could ncrwhere find the cm- responding work of these auth~ors.

The second method which I mentioned is more difficult, (because one has to demonstrate the activity of the nervous centers while stimulating afferent nerves. But what means of showing an active state do we have? Stimulated muscle changes its shape and, with the help of the myograph,

2 CHARCOT: Localization of diseases of brain. German translation, 1878, p. 40 and 41.

DOCTORAL THESIS 9

a very accurate picture of its state can be obtained; in the active gland, secretion is increased. During activity, peripheral nerves, which show no visible changes, have with muscles and glands the feature in common that, with a change in the electric potential within them, a current is produced which affects the strength and the direction of the current existing in the muscles and glands, and can be conducted to a galvanometer by means of appropriate electrodes. Since the current generated when the tissue becomes active usually has an apposite 'direction to the original current, the change in current was termed negative variation.

The questions arise of whether there are such currents in the nervous centers - in the brain and spinal cord, of whether in the active state changes occur in these currents, and of whether, by means of determining such changes, it would be possible to demonstrate a state of activity in certain parts of the central nervous system. Even a priori lone could say yes, with a high degree of probatbility. ,4nd indeed, experiments carried out by Sechenov, Verigo and Wedengky, to which I wilil return later, seemed to support it; they also motivated Wedensky during the Russian congress of physicians and biologists in Petersburg to express a theory that the method of negative variation could by used to d e tennine localizations on the cerebral cortex. The experiments will show to what extent the theory can be substantiated. However, before I proceed to describe them, I would like to give a 'brief sketch of the history of the science of localization, in particular, about the determination of localization through demonstraticms of changes in the currents of the central nervous system.

Seldom has any field of physiology wiltnessed such an extensive literature as the science of l~calization of activity of the cerebral cortex, in spite of its being very yomg as a science. Some 20 years ago, physilcl- logists still generally assulned that various pasts of the brain cortex were equally important with reslped to activity. This assumpltion was based on facts known from pathology, where extensive damage d some parts of the hemispheres often produced the same abnormality of functions, or where pathological changes in the brain found at post mortem did not produce any symptoms during life. The prevailence of that assumption and the faith in it were the inevitable consequences of readion against the principles propagated by Gall, who brought the science of locallization to absurdity, so that afterwardis any opposing theory was not even discussed. Only with difficulty could this assumption be 'challenged by in- disputable facts ~uppcrrti~ng the localizatilon; facts which were made generally known by authors from time to 'time. Thus, in 1825 Bouillaud 3

"OUILLAUD: Trait6 clinique et physiologique de IYenc6phalite. Paris 1825.

10 A. BECK

expressed the (opinion, (based on post -em results, that the centers for articulation of words are situated in the frontal labe of the hemispheres, and ten years later, Dax 4, also on the basis of post mortem results, demonstrated that only the left frontal lobe could be considered the center for speech. Broca 5 described the center for speech more precisely, showing that it is in the third left frontal mnvolu~tion. The anatomical investigations of Meynert also spoke against the equiponderance of all parts of the brain; according to this work, the paths of the afferent nerves are directed more towards the posterior parts of the cerebral cortex, and the motor nerves, towards the anterior parts.

The science of localization of functions on the cerebral cortex entered a new phase, when Fritsch and Hitzig 6, and also Ferrier 7 succeeded in obtaining well defined and narrowly localized functions of muscle groups by stimulation of certain specific areas of the cortex. As I mentioned at the beginning, experiments wilth the method of stimulation leave much to be desired with respect to accuracy. Thus, Hermanna emphasizes all the objections which I have mentioned, and Coufty 9, excluding the cortex by extirpating it or by ligation of its vessels, obtained the same results by stimulation of the white matter; on ithe basis of his experiments he assumes that stimulation of the m t e x results iln stimulation of nerve fibres in the white matter passing beneath the point of stimulation.

After the publications of Ferrier, Fritsch and Hitzig, many other publications appeared which described experiments on various animals, of which the most important are the experiments of Munklo, who experimented mostly with dogs, using the ex%irpation method. He cut circular discs of an average diameter of 15 mm and up to 2 mlm deep from the cortex of the occilpital, temporal and parietal ,regions, first in one hemisphere, and then symmetrically in both hemispheres. Munk reports the following results of his experiments: if we draw an imaginary line from the fissure of Sylvius, perpendicular to the Rolandic fissure, then extilrpations in the entire pad of the cortex lying anterior to the imaginary line result in motor defects, but damage of the cortex outside

4 DAX: Congds mbd. de Montepeiller, 1836. BROCA: Bull. de la Soci6tC anatom. de Paris, 1861. FRITSCH and HITZIG: Arch. f. Anat. u. Physiologie, 1870.

7 FERRIER: The localization of function in the brain. Proceed. Roy. Soc. XXII. HERMANN: Pfliigers Arch. X.

0 COUTY: Sur la non excitabilitk de 1'6corce grise du cerveau. Comptes rendus LXXXVIII.

'0 MUNK: Zur Physiologie der Grosshirnrinde. 4 Mittheilungen an die physiol. Ges. in Berlin, 1876-1878. Arch. f. Anat. u. Phys. 1878. Berl. klin. Woch. 1879.- Sitzungsber. d. k. preuss. Akad. d. Wissenschft. 1883, 1884, 1886 and 6889.

DOCTORAL THESIS 11

those limits, although never causing any motor changes, always results in loss of sensory functions. For instance, destruction of cortex in the occipital lobe, denoted by Munk with 'the letter A, results in blindness of the opposite eye 11; destruction of cortex in the temporal lobe, B fbi- laterally, because a unilateral extirpation is ineffective for this purpose), results in deafness; destruction of the hippocampal gyri leads to lms of the sense of smell. Sim$lar results were obtained by Munk f m experiments with the brain of the horse.

From Munik's experiments on small mammals (rabbits, guinea pigs, rats) and on pigeons, it appears that the functions of the cortex are rmt so precisely localized, becaulse the author was not able to produce blindness in those animals by excising the occipital lobe, and only the complete removal of the whole hemisphere resulted in blindness of the opposite eye. Munk thinks that the visual part in lower mammals and birds is much greater, and that it gradually becomes progressively more limited in the more highly developed animals. Moeli 12, however, by applying heat selectively to the rabbit cortex, found visual and somatosensory regions on it. In his operated animals, vision lost after the extirpation of the visual region returned slowly and did not disappear after destruction of the same region on the other hemilsphere. Nothnagel13 was awe to demonstrate the motor regions by destmroying limited areas on the cortex by injection of chromic acid with a Prawatz syringe through a fine opening in the skull. Paralysis which ensued in those animals after the destruction of the cortex disappeared if the animals remained alive for a few weeks.

I do not want to weary the reader with descriptions of all the experiments perfiormed on animals 14, but I would like to add only that recently the English school, mainly Horsley, brought the experimentation with cerebral cortex, especially with its motor regions, to perfection. Thus, a t the last International Congress of Physiologists in Basel, Horsley (and Beevor) 15 produced the finest movement of the thumb, fingers, arms, lids, eye, tongue, etc., in Macacus sinicus, by stimulation of d i f f m t regions of the cortex.

On the basis of all these animal experiments, it is now accepted that

11 In his later experiments MUNK became convinced that in the dog, in the same way as in the monkey and in man, the nerve fibers from both retinae project to the occipital region of the cortex, and hemianopsia is the consequence of destruction of the occipital lobe. However, the hemianopsia is not as well defined as in man.

l2 MOELI: Arch. f. pathol. Anat. LXXVI, 475-485, Table VIII. '3 NOTHNAGEL: Arch. f. pathol. Anat. LVII. Experim. Untersuchung iiber

die Functionen des Gehirns. " BOCHEFONTAINE and VIEL, VULPIAN, and others. '5 HORSLEY and BEEVOR: Zentralblatt f. Physiologie, 1889, No. 14.

12 A. BECK

the cerebral cortex of animals is divilded into two parts: motor and sensory. The first occupies the anterior part, the second, the posterior part, and is divided into the visual region (occipital lobe), the auditory region (temporal lobe), and the olfactory region (hippocampal gyrus). The sites of the sensory centers for the skin (especially for the nerves of touch), accvrding to the authors, are situated in the motor centers which control the muscles of the correspcmding part of the body.

More exact clinical and anaftmo-pathological investigations eventually permitted the same thesis to be applied also to man; in these studies, the French school, of which Charcot is the chief representative and founder, excelled. Not only dimd Charcot himself initiate rigorous studies on bcalization but forcefully inspired many young men to take up this important problem, and in this way a whole series of valuable publications 16 appeared from the Salpetrii.re, which contributed importanltly to our information on the location and properties of the psychomotor and sensory centers in man.

Despite these numerous convincing investigations, there are still o p p nents of the science of localization. The ~ o p p i t i o n is represented by Goltz 17, who removed parts of the cortex in animals (by flushing them out with a strong stream of water introduced with a cannula under the cortex. He maintains that functional disturbances of animals (operated in this way depend only lm the extent of the resulting loss, and not at all on the location of the injury on the cortex, for example, that from the point of view of changes in functions, it is the same whether the so- called motor, or sensory part was destmyed. Hitzig 18 and Munk le. however, think that the destructi~ons which Goltz carried out with his method are too extensive and injurious for its results to be compared with the results of their method of extirpation. But Goltz still persists with his method, and even at the last Congress of Physiologists in Basd (1889) 20

demonstrated a 'dog with a resected left hemisphere, the behavior of which purportedly differed little f m that of a normal dog. I have it privately from Professor Cybullski, h'owever, who attended the meeting, that the dog showed certain differences in lbehavior from that of a normal dog. Apart from the fact that it always began each act with the left paw (digging up meat from sand, etc.), the sensation in the right paw was impaired, with the result that the dog maintained ,the paw in whatever awkward position it was brought to.

BOURNEVILLE, BALL, PITRES, DUSSAUSSAY, and many others. l7 GOLTZ: Archiv f . die gesammte Physiologie, XI11 and XIV. '8 HITZIG: Arch. f. Anat. und Physiologie, 1876.

MUNK: op. cit. *O GOLTZ: Zentralblatt f. Physiologie, 1889, No. 14.

DOCTORAL THESIS 13

Recently, Wundt 2l also tmk issue with the science of localization, maintaining that the variety of sensory impressions does not depend upon the heterogeneity of the central sensory apparatus, but u p m the heterogeneity of molecular processes which arise as a result of cdifferent external stimulations of the sensory nerves and evoke different processes in the centers. I t is true, in Wundt's opinion, that under ordinary conlditions, each functim has a specific locus in the central nervous system, and certain centers acquire greater proficiency for certain functions, if the external stimuli remain more active. Hlowever, far the centers the functions sf which remain suppressed lor abolished, others can function instead, if they are connected with the appropriate external organ or with the appropriate center.

Wundt attempts to derive his theory from the history of the evolution of nervous system.

Despite the extensive literature on the science of localization, the topic of our dissertation, the determination of functifons of nervous centers by the use of changes occurring in the currents in them, although it is not very new, has so far been little explored. I can quote on!ly two authors who discussed this problem; as we shall see, even they were only ap- proaching the main subject.

One of these authors, Sechenov " , r ecod ing neural current from transverse and longitudilnal secltims of the spinal cord of a frog, observed that (i) the current increases in the first moments, for the negative voltage requires a certain time to be generated; (ii) subsequently, the current decreases, and that decrease can be accelerated or evoked by stimulation of the sciatic nerve (consequently this is negative variation caused by stimulation of the cord by an afferent nerve). Similar, even more remarkable changes in the current were seen by Sechenov on transverse sections of the medulla oblongata. Here, negative variations arise either spontaneously or from a single stimulation of the sciatic nerve. The spontaneous variations appear mostly in the upper sections of the medulla oblongata, and the author therefore thinks they are i,mprtant to the functions of that part of the central nervous system, and indicates a spontaneous excirtatilon of the nervcrus centers which are there, pm- bably the respiratory centers.

At the consess of Russian physicians a year ago, Verig023, referring to the above-described experiments of Sechenov, announced that con- necting the lumbar enlargement of a frog's cord and another, arbitrary

21 WUNDT: Grundziige der physiologischen Psychologie, 1887. 22 SECHENOV: Archiv. f. die ges. Physiologie XXV. 23 VERIGO: Vrach 1889, No. 2. Report of the I11 Congress of Russian Physicians

at Petersburg.

14 A. BECK

point on the cord to a galvanometer resulted in a deflection of the galvanometer needle for each stimulation of the paw, showing that a negative voltage d s e s in the lumbar enlargement as an expression of an active state in that location. Similarly, Verigo was able )to ascertain that the anterior part of the hemispheres became electronegative if the hind Begs are moved. Hence, assuming that the centers become eledm- negative wherever an active state arises in nervous centem, one could determine ldizatilons m the cerebral cortex with the aid of determination of negative variation, as was emphasized during the Congress.

Homley 24 also experimented with the negative variation in the spinal cord; his work is not, however, directly connected with the question concerning us here. In this work, performed w'ith Ciotch and described at the Congress of Physiologists in Basel, the authors determined the negative variation first in the sciatic nerve, stimulating that part of the cortex from which the movements of the hind legs result. In the same way, by stimulating the same part of the contex, they obtained a negative variation of the current recorded from the proximal part o~f the trans- sected cord. The experiments were carried out on monkeys, the resting current and the negative variation being shown with the aid of a Lipp- mann mercury electrometer.

Before presenting the results of my experi~ments, I want to say a few words about their organization.

To conduct the current away from the cord or brain, I wed nonpolarizing electrodes as described by du Bois-Reymond, slightly modified; they were made from a fine clay saturated with a lVo solution of sodium chloride and set in the form of a plug on a glass tube filled with a cun- centrated solution of zinc sulfide. An amalgamated zinc wire was in- serted into the glass tube, and all this was mounted on a heavy brass stand, the pedestal of which was insulated with rubber. From one such electrude the wire went directly $0 the galvan~ometer, the second wire went to the movaMe conbet of a rheostat, one end of which was connected to the second wire of the galvanmeter. The two ends of the rheostat were connected with wires to a Daniel1 cell for balancing current. Needless %o adsd, by means of a switch, the direction of the compensating current could be changed as needed, or, elilminated in the connection between the nonphrizimg electrodes and the galvanometer. Opposite the

24 HORSLEY: Zentralblatt f. Physiologie, 1889, No. 14.

DOCTORAL THESIS 15

mirror of the galvanlmeter, at a distance of 330 cm, there was a tele- soope t h m g h which the divisiom of a scale suspended a b v e it were read. The sensitivity of the Wiedemann galvanometer25, modified by Hermann, was calculated by a physics assistant in the Jagiellonian Univer- sity. With the coil of the rheostat sho.rted, 1 cm on the scale (when the distance from the galvanometer mirror was 288 cm) corresponded to

43 Ampere. 10,000,000,000

EXPERIMENTS ON THE SPINAL CORD

These experiments were performed only on frogs. The cord and the brain were exposed in the bony canal with extreme calre, leaving intact the connections with the hind legs, the sciatic nerves of which had been exposed previously. I then excised the rest d the body d m usually to the level of the lumbar enlargement, and placed the entire preparation, consisting of the 'brain, cord and the hind legs, on a cork b e in such a way that the brain and cord rested on a glass plate to which they were conveniently affixed. If the preparation was a good one well prepared, the hind 'legs, together with the sacral bone, performed n o d , m- restricted movements. Platinum electrodes were placed under the sciatic nerve, which was cut distally, for stimulating the proximal part of the nerve, be means of a Du Bois-Reymond coil. The above-descriibed nonpolarizing, electrodes were then applied to two selected points of the nervous system. All of this was m e r e d with a bell-jar, under which wet pieces of cotton were placed to prevent the preparation and the electrodes f m drying out. In this way, one could observe the current arising from the interoonnection of two different points of the central nervous system, determine its strength and direction, observe for m e time the spontaneous behavior of the current and changes in it produced by stimulation of the system through the intermediary of the sciatic nerve. The bell-jar was lifted only for moving the electmdes to another location so as %o examine the latter. The arrangement was found to be so satisfactory that often after 2 hr of experimenting, the nerve, spinal cord, and brain behaved as though they had been freshly prepared.

Having thus descri'bed in outline the course d the experiments m frogs, I will now present the result. However, since on mlost of the frogs I examined not only the a d itself but also the behavior of the nervous current in the cerebral hemispheres, the optic lobes, corpora bigmioa

45 The galvanometer I used comes from the factory of J. Meyer in Ziirich.

16 A. BECK

and medulla oblongata, I will describe them as a whlole, s o as not to return to the same experiments when describing the studies on the cortex and on the medulla oblongata.

Experiment I

a) Electrode A, on the anterior part of the cerebral hemispheres; Electrode B, on the thoracic part of the cord. Distance between electrodes, 18 mm. Right sciatic nerve was exposed fox stimulation:

The deflection 'of the mirror expressed in milimetern on the scale, + 60 26. During stimulation of the sciatic nerve, + 61.

b) After excision of the hemispheres, Electrode A was placed on the transverse section of the anterior limits of the optic lobes; Electrode B was left unchanged. I n t e r ~ l e c t d e distance, 12 mm:

Deflection, 83; with stimulation d the sciatic nerve, 83.

c) Electrode A at the level of the medulla dblongata; Eledrode B unchanged; interelectde distance, 9 mm:

Deflection, 86 ; during stimulation of sciatic nerve, 108.

After cessation of stimulation, 108 (deflection did not decrease). Deflection, 119;

with stimulation, 135. After cessation of stimulation, 115.

This experiment demonstrated that the higher parts of the central nervous system are electronegative when compared with the lower parts, without regmd to where the current was led off f m the undamaged parts in the proximal portion or from the transverse section. I stress this point because, as we shall see, it was true in nearly all of the experiments.

Experiment I1

a) Electrode A on the anterior podion of the left hemisphere, B on the p t e r i o r portion of the right hemisphere. Stimulation of the right sciatic nerve:

To explain the numbers given here and subsequently, I should mention that the scale which I used in the experiments was one meter long with the zero point in the middle and 500 mm division on each side. The part of the scale situated to the left of the person looking into the telescope I consider positive, the other side, negative.

DOCTORAL THESIS

Deflection, 45 ; during stimulation, 45.

After a few minutes, 35; during stimulation, 35.

b) After relocation of the electrodes on the anterior portion of the right hemisphere and the posterior portion of the left, the stimulation also gave a negative result because the deflection of 46 mm for this placement did not change during stimulation.

c) Hemispheres excised. Electrode A an the transverse section, B on the medulla; interelectrode distance, 5 mm:

Deflection, 56; during stimulation, 56.

d) Both electrodes situated very low on the cord, separated by 3 mm:

Deflection, 58 ; during stimulation of sciatic nerve, 53.

After cessation of stimulatim, 58; during stimulation a second time, 54.

After a few minutes, during which the current to the galvanometer was interrupted :


After stimulation, 57 ; during stimulation, 53.

Experiment I I I

Cerebral hemispheres excised. Electrode A on corpora bigmina, B m the medulla. Interelectrode distance, 8 mm.

Deflection (to the negative side): - 154, - 143, - 137, - 128; during stimulation, - 120.

After cessation of stimulation, the current, which had a direction different fmm that in other experiments (i.e., the upper portion was electropsitive relative to the lower portion), suddenly reversed; it was so strong that the scale went completely out of the field of the telescope in the positive diredim. I denoted this by 500-1°/o, and as a result I used the compensation and brought the scale to zem. The current remained persistently strong, such that after a few minutes, the deflection again went off scale after removal of the compensation:

Deflection, 500 4- O/o; compensated to 0; during stimulation of sciatic nerve, - 210;

after cessation of stimulation, - 180.

2 - Acta Neurobiologiae Experimentalis

18 A. BECK

After a little time, the current reversed so that the scale shifted to the negative side (-O/o).

Compensated to 0; stimulation, 20; after cessation of stimulation, 0; repeat stimulation, 25; after cessation of stimulati,on, 0.

Finally, the current changed once again, such that the upper part became electronegative :

Deflection, 500 + O/o; compensated, - 5; during stimulation, 55;

after cessation of stimulation, - 5; stimulated, 105;

after cessation of stimulation, -5; stimulated, 98.

In this case, as we see, the so-called resting current underwent various changes. We will return to these changes later, when an attempt will be made to explain them. For the present, I would like only to call attention to the experimental difficulties which are encountered in these experiments, as well as to indicate how easy it is to fall into error and draw erroneous conclusions from a superficial evaluation of the results.

Experiment IV

a) Electrode A on the left corpora bigemina (the hemispheres were excised beforehand, the electrode, however, did not rest on the cut surface); Electrode B placed on the thoracic part of the mrd. Interelectrode distance, 12 mm. The right sciatic nerve was exposed for stimulation.

Deflection, 280; compensated to 0; during stimulation, - 20, - 23, - 37.

After cessation of the stimulation, the current remained unchanged, from which one can conclude that the change in the resting current was unrelated to the stimulation. To ascertain whether this were actually so, I repeated the experiment, and found heed that stimulation of the sciatic nerve had no influence on the current led off from corpora bigemina and the higher parts of the cord.

Deflection, 251; co,mpensated to 0; during stimulation, 0.

DOCTORAL THESIS 19

b) Electrode A on the right corpora bigemina, B on the same location on cosd as at first. The results are the same as the preceding.

Deflection, 336; compensated to 0; stimulation, -4; after stimulation, -4, -8, -11.

c) Electrode A on the lower part of the medulla, Electrode B as in a) and b); both in contact with the right side of the cord (the sciatic nerve was stimulated as well). Interelectrode distance, 8 mm.

Deflection, 161; compensated to 4; during stimulation, 4.

The position of the electrodes was then changed to the same points on the left side; the results were similar:

Deflection, 461 ; compensated to -4; during stimulation, the current decreased to -26, to be sure, but after stimulation it did not return to the previous strength.

d) Electmde A close to the cervical enlargement; electrode B on the lumbar enlargement. Interelectrode distance, 15 mm.

Deflecti,an, 185; during stimulation, 155;

after stimulation, 195; during repeat stimulation, 160 ;

after stimulation, 192; during repeat stimulation, 165.

(See Fig. 1.)

Experiment V

a) Hemispheres intact. Electrode A on the left corpora bigemina; B a t a distance of 12 mm on cervical enlargement, also on the left; right sciatic nerve stimulated.

Deflection, 460 ; compensated ko + 3 ; during stimulation, - 5 ;

after stimulation, + 5; during repeat stimulation, 0.

b) Electrode A on the right corpora bigemina, B on the same place as before.

Deflection, 162; during stimulation, 155 ;


20 A. BECK

after stimulation, 159 ; during repeat stimulation, 155.

c) Electrodes situated as in a), except that both were placed on the left side, while the sciakic nerve was stimulated.

Deflection, 235; compensated to 0; during stimulation, - 2 ;

after stimulation, + 1 ; during repeat stimulation, 0.

d) E l e c t d e A on the left hemisphere; B on the cervical part of the cord. Interelectrode distance, 15 mm.

Deflection, 128; during stimulatim, 133;

after stimulation, 130; during repeat stimulation, 133.

e) Electmde A below the cervical enlargement, Ellectrode B above the lumbar enlargement. Intwelectmde distance, 8 mm.


compensated to 0; during stimulation, 0.

f) Electmde A on the medulla oblongata, Electrode B on the lumbar enlargement. Interelectrode distance, 20 mm.

Deflection, 325; compensated to 0.

The mirror of the galvanometer did not stop, but proceeded in the positive direction +5, 8, 12 .... To ascertain whether the current led off from the cord was continually increasing, or the compensating current was losing strength, I eliminated the compensation, and ascehined that in this case also the scale went in the positive direction, and hence the current of the card evidently increased, since the deflection was 140, 142, 144, 145, etc.; after repeat mpensatilon it was 0, 7, 11, 15. Stimula- tion of the sciatic nerve had no effect on the behavior of the current.

Experiment VI

The brain was excised just above the medulla oblongata. Both electrodes placed at a distance of 3 mm from one another between the cervical and lumbar enlargements, contacting the m d on the left side. The right sciatic nerve was exposed for stimulation.

DOCTORAL THESIS

Deflection, - 34; during stimulation, - 45;

after stimulation, - 3 4 ; during repeat stimulation, - 35.

The f a d that the current here was opposite to that in all the other experiments (i.e., the lower portion of the cord was elec~negative) indicates that the cord was damaged at the site of contact of Electrode B ; this was confirmed after moving Electrcule B to the right side of the lumbar enlargement; the current changed its direction to that which I had thus far dbserved:

Defledion, 63; during stimulation, 56 ;

after stimulation, 6 6 ; during repeat stimulation, 46;

after stimulation, 7 3 ; during repeat stimulation, 56.

During 1.5 min of stimulation, the negative variation began to di- minish, and the scale s lmly returned to 7 4 .

I repeated the experiment several times, always with the same result:

Deflection, 61 ; during stimulation, 47 ;

after stimulation, 6 1 ; during stimulation, 49;

after stimulation, 6 6 ; during stimulation, 56.

(See Fig. 2.)

Experiment VII

Hemispheres excised. Electrode A on the left corpora bigemina, Elec- trode B on the left side d the medulla oblongata. Interelectde distance, 3 mm. The right sciatic nerve exposed for stimulatim.


Both electrodes then transferred to the same points but on the right side. Interelectrode distance, 3 rnm.

Deflection, 402; compensated to 0; dwing stimulation, 0 .

The current continuously lost strength so that the defleuticm, for the same compensation, was -20 after a few minutes, and stimulation of

22 A. BECK

the sciatic nerve had no effect at all on the behavior of the initial current.

b) Electrode A on the left optic lobe, Electrode B on the left side of the lumbar enlargement. Interelectrode distance, 18 mm.

Deflection, 476; compensated to 0; during stimulation, 0.

The current increased steadily; during stimulation, the mirror stopped, despite a constant tendency to continue.

c) Electrode B on the lumbar prominence, Electrode A 2 mm higher, both on the right side.

Deflection, - 110; during stimulation, - 96.

d) Electrodes in same positions as the preceding, but on the left side; left sciatic nerve stimulated:


after stimulation, 167; during repeat stimulation, 148;

after stimulatim, 160; during repeat stimulation, 152.

Despite further stimulation, it began to return to 162; after a short pause, stimulation caused a negative variation to 142. *

(See Fig. 3.)

Experiment VZZZ

a) Electrode A on the medulla oblongata (the brain is intact), Elec- trode B on the thoracic part of the cord. Interelectrode distance, 12 mm.

Deflection, 74; during stimulation, 77;


after stimulation, 85.

b) Electrode A on the left cerebral hemisphere, B on the left corpora bigemina. Right sciatic nerve used for st.imulation:


c) A on the medulla oblongata, B on cervical cord. Interelectrode distance, 9 mm.


DOCTORAL THESIS

d) A on the medulla oblongata, B on the lumbar enlargement.


e) Brain excised just above the medulla. Electrode A is placed on the cut surface, B on the thoracic enlargement of the cord:

Deflection progressively increases from 66 to 88; stimulation was without any effect.

f') Electrode B was placed cm lumbar enlargement, A remained on the cut surface.

Deflection, 89; during stimulation, 83, in spite of a tendency to move toward the positive side; after stimulation, 91; during repeat stimulation, 85.

Experiment ZX

Brain excised above the medulla oblongata.

a) Electrode A on the cut surface of the medulla, and B on the lumbar enlargement; interelectmde distance, 9 mm. Current very strong.

Deflection, 500 +O/O; compensated to 0; during stimulation, 0;

After stimulation, - 4 ; during sltimulation, - 4.

b) Both electrodes in the vicinity of the thoracic enlargement of the cord, separated by 1.5 mm.


c) Both electrodes in the vici,nity of the lumbar enlargement on the left side (right sciatic nerve was stimulated); interelectrode distance, 2 mm.

Deflection, 39; during stimulation, 36; After stimulation, remain a t 36.

d) Both electrodes a t the same level but on the right side.

Deflection, 43; stimulation, 40.

e) The cord is cut above the lumbar enlargement; Electrode A placed on the cut surface, Electrode B placed 2 mm lower.

Deflection, 127, 130, 135; stimulated, 130; after stimulation, 135; stimulated, 132 ;

24 A. BECK

after stimulation, 133 ; stimulated, 129 ; after stimulation, 131 ; stimulated, 126.

Experiment X

a) Electrode A on the anterior part of the hemisphere, Electrode B on the lumbar enlargement. Interelectrode distance, 22 mm; right sciatic nerve exposed for stimulation.

Deflection, 500-k0/o; compensated to 0; during stimulation, -52; after stimulation, - 3 ; during stimulation, - 37 ; after stimulatilon, - 2.

b) Electrode B shifted to the thoracic part, which evidently was damaged, because the direction of the current was opposite to that in other trials.

Deflection, -450; compensated bo 0; during stimulation, 0.

c) After shifting Electrode B 1 mm posteriorly to an undamaged location and placing Electrode A on the posterior part of the hemispheres; electrode separation, 10 mm.

Deflection, 180; during stimulation, 180; deflection, 190 ; during stimulation, 190 ; deflection, 189; during a longer stimulation, the variation persisted:

188, 189, 187, 189.

d) Electrode A on the anterior part of the hemispheres, B as in c). Electrode separation, 13 mm.

Deflection, 155; despite persistent stimulaticon, 155;

after stimulation, 155; despite persistent stimulation, 155.

e) Electrode A an the thoracic part of the cord, B on the lumbar enlargement.

Deflection, 500 4- O/o; compensated to 0; during stimulation, - 24; after stimulation, 4- 16 ;

during stimulation, - 6 ; after stimulation, + 11 ;

during stimulation, - 6.

f) Electrode A applied to the medulla oblongata, Electrode B on the thoracic part of the cord a t a distance of 3 mm from the first. After the deflection reached 74, it shifted slowly toward the positive side so that, after 2 min, the deflection was 78, and after another 5 min, i t was 88; during that time no variations were observed.

DOCTORAL THESIS 25

g) Finally, the medulla oblongata was sectioned, to which Electrode A was applied, while Electrode B remained in its previous position.

Deflection, 500-t0/o; after compensation to 0, in 10 min, an increase in the deflection was observed, after which time it went from 0 to 86; stimulation of the sciatic nerve was of no influence on 'the deflection.

Experiment XI

Brain excised above the medulla.

a) Electrode A on the cut surface of the medulla and Electrode B on the cervical enlargement of the spinal cord. Interelectrode distance, 8 mm. Left sciatic nerve exposed for stimulation.

Deflection, 500 + O/o; compensated to 0 ; the deflection decreased slowly with small variations such that after 10 min, it was -40 (mpensated), then -60 after another 5 min, and after another 5 min, among msi~der - able variations, 101. Stimulation of the sciatic nerve did not affeat the deflection.

b) Electrode B placed on the lumbar enlargement, A remained unchanged; separation, 16 mm.

Deflection, 500+0/o; after compensation to 0 there were small variations, among which, after 3 min, the defleotion reached 12.

After stimulation of the sciatic nerve, a negative variation to -9 occurred; after stimulation, the deflection returned to 11; after repeat stimulation, - 8; after cessation of the latter, 11.

To better demonstrate the results of the experiments, and to help the reader to orientate himself among this profusion of numbers, we present some of the more important results graphically, positive deflections indicated by an ascending line, and negative deflections by a descendimg line. The graphs are not intended to be a strictly accurate representation of the deflections and their variations, because I could not take into account the very important factor of time, with which both the deflections and the variations occurred. In any case, I hope that graphs will help in familiarization with the results of the experiments.

Figure 1 shows the changes in deflection resulting from the stimulation in Experiment IVd, Fig. 2, the results of Experiment VI, Fig. 3, Ex- periment VII, and Fig. 4, Experiment XIb.

Having set forth the results of a substantial part of the experiments, we must next examine their significance and consider what conclusions can be drawn. I consider analysis of the results all the more necessary because, except for the previously mentioned work of Sechenov and

26 A. BECK

Verigo, I did not find any mention of the existence of currents in the central nervous system in the more recent literature available to me, not to mention the investigation of the characteristics of the currents and their behavior toward various external factors. Even then, the work of Sechenov, as a provisional report, was not followed up by a more extensive description of the experiments, and likewise the short reference by Verigo to his experiments does not discuss the problem sufficiently extensively. The question is therefore altogether new and as such requires searching attention.

Since the currents arising in the central nervous system are wi-thout question analogous to the electric currents in nerves, and since the latter have been carefully investigated, it will be only appropriate on this subjeat to recall the reasons for the existence of the currents in nerves.

If we connect the cut surface of a nerve and any point d its intact longitudinal portion to a suitable instrument (compass, electrometer, tele- phone or a nerve connected to a muscle) by means of a good conductor of electricity, we can demonstrate the existence of a current, the direction

Fig. 1.

170

160

Fig. 3.

L

DOCTORAL TIIESIS 2 7

of which shows that points on the cut section are electronegative relative to the point on the longitudinal portion. The current existing in the nerve is called a resting current in contradistinction to the action current (Actionsstrom) arising whenever the nerve becomes active. The negative variation of the resting current, arising during stimulation of the nerve, is the expression of this action current. The most probable reason for the existence of the resting current is the earlier necrosis of the elements at the cut surface of the nerve; during stimulation of the nerve the elements which become active, similarly to the dying ones, become electronegative in relation to others, and in this way, generate the current.

The question arises first of all of whether the current observed in the central nervous system is a resting one, or, an active one. Hennann 27

gives as a physiological axiom the theorem that the resting current is only an expression of injury and he maintains that from a connection between two undamaged points on the nerve no current can be obtained. Hennann based his theorem, which is accepted almost universally by physiologists, on experiments performed on nerves of a certain animal (tench), of which the optic nerve ends with a sort of natural cut surface, and from a connection between that termination and a longitudinal portion, no current could be obtained. Pmeeding from this view, we could then term the current of the central nervous system a resting current only if it were obtained by interconnecting the injured point with an intact longitudinal portion. This, however, was not the case.

Of course, the regularity with which the electric potential of the higher levels of the nervous system existed with respect to the lower levels speaks against the possibility that the potential is the consequence of the transsection. If anything, a t most one could say about the lower parts of the nervous system only that they were subject to damage, and that the sectioning of them occurred from cutting the spinal nerves, whereas the anterior (or posterior) surfaces of the cerebral hemispheres, the corpora bigemina, and the medulla oblongata (and I applied the electrodes only to their anterior [or posterior] surfaces) were certainly not damaged, because they were easy to expose and separate, and no nerves emerge from their superior surface.

If a current were the result of changes in the electric poltential caused by the artificial sectioning, then the lower part should be electronegative relative to the upper one. Moreover, we know from neurophysiology that any current formed by the connection of the cut section with the longitudinal portion loses strength rapidly, as a result of which the potential of negative electricity decreases as the degree of necrosis of the nerve

27 HERMANN: Handbuch der Physiologie, Vol. 11.

28 A. BECK

elements progressively diminishes. We did not observe such a decrease of the current except after a long time, when the brain and mrd began to die. Finally, spontaneous variations such as we observed here never occur in the current from transverse and longitudinal sections of a nerve. It follows, therefore, that the current observed in the central nervous system was an action current. To differentiate this current from the current resulting fmm stimulation, I would suggest the name of spontaneous action current. The f a d that the superior parts were always negative relative to the inferior parts suggests that that current was an expression of an active state arising in the higher parts of the nervous system. In a word, we are dealing with in autonomous excitation of the nervous centers.

In a few of the experiments (me of which I described under Experi- ment 111), I noted that the current suddenly reversed its direction. This occurred especially with transverse sections. Because the direction of the original current. was different from usual (upper portion pxitive, Lower negative), I think I am not far from the truth in assuming that the sectioning itself aould have been the reason for the unusually strong inhibition of the centers, in which only after the inhibitory effect was removed, muld their active state be expressed (in Experiment 111, the hemispheres were excised just anterior to the inhibited centers them- selves - the optic lobes - which could thus have been subjected to intense excitation).

Another point to be dilscussed is the effect on the action current of the stimulation of the proximal end of the sciatic nerve. We observed that there occurred either an increase or a decrease in the strength of the current during the stimulation of the sciatic nerve. An increase in strength indicated that the higher centers became more electronegative, that is to say, their state of adivimty became more prominent. In other words, from the increase in the original deflection which occurs during stimulation of the sciatic nerve, we can infer that the centers in places where the electrode was nearer to their central part were also activated by the stimulation of the sciatic nerve.

Let us have a look at those experiments in which this event t w k place: in Experiment Ic, during stimulaticm of the sciatic nerve, the electronegative voltage increased so much 'on the cut surface of the medulla that the deflectiton increased by 16 mm. Similarly with the active state of the medulla in Experiment 111, where, after compensation, the deflection during stimulation was initialy 55, and then even 105. The deflection of 5 mm in Experiment VId, and also the deflection of from 3 to 5 mm in Experiment VIIIa, shows that a decrease in the state of activity was produced on the hemisphere during stimulation.

DOCTORAL THESIS 29

The second change which we observed in the current during the stimulation of the sciatic nerve was, as I mentioned previously, a diminution in strength of the original current, that is, a negative variation in the strict meaning of this term. The reason of the negative variation can be either the decrease of the electmnegative potential in the upper part of the central nervous system (or what is the same thing - inhibition of the functions of the centers situated here), or, the appearance of an electronegaitive potential a t a lower level where it was positive before, which once again is really identical with a transition (of the centers situated there into an active state. Considering that such a negative variation, as can readily be ascertained from the experiments described, appeared during stimulation of the sciatic nerve when electrode B was placed on the l m b a r enlargement of the spinal cord, we can justifiably assume that the stimulation of the nerve evoked an active state in the sensory and mobr centers, that is, in the reflex apparatus, situated in the lumbar part of the cord.

My dducrtims may meet with the objection that the negative varia- tilon in these cases did not arise in the centers but in the nerve fibers, which, as a further continuation of afferent pathways running f m the sciatic nerve t~ the brain through the cord, conduct +the active state during stimulation of that particular nerve. This objection, however, will not withstand criticism for the following reasons: firstly, Hermann has already demonstrated, in the experiments cited previously, that two longitudinal portions 'of a nerve, i.e., an uninjured nerve, will not produce either a resting current or a negative variation (with mly certain ex- ceptions, and those under special conditions, for example, while cooling a nerve one can observe a current); secondly, a negative variatim, which if caused by an active stake in nerve fibers would be transferred in the proximal direction, should also be demonstrable (although to a lesser degree) in the upper parts of the cord, i.e., in the thoracic part. However, it is obvious from the experiments that such a negative variation did not appear in the cervioal or thoracic parts of the cord.

In connection with the experi~nents on the brain and cord of the fmg, I may mention briefly the experiments of Sechenov. He was actually concerned with the sum of the resting and action currents, because he led off the current from the transverse and longitudinal sections of the cord. The two last experiments I described are repetitions of Sechenov's experiment. One can easily be mvimced that in conformity with Seche- nov's statement the current increased and the slowly decreased, but it did not show any sudden variatim. The r e a m s for the negative variation during stimulatim of the sciatic nerve can easily be understood by looking at Experiment XI. In the latter, an active state was produced in

30 A. BECK

the lumbar enlargement during stimulation of the nerve, which was the cause of diminution of the initial current, as I indicated previously.

In the end, I have to agree with the observations of Sechenov that the spontaneous current, and also the constance of occurrence of the negative variation, is very changeable, depending upon the sensitivity of the central nervous system. Foremost was the difference between fmgs kept in the Institute all winter and fresh spring frogs; in the former, the deflection caused by the spontaneous current was insignificant (only a few or several centimeters), whereas in the latter, one had to use a relatively strong current t o compensate for the spontaneous current (after dis- appearance of the scale from the field of vision).

EXPERIMENTS ON THE CEREBRAL CORTEX OF WARMBLOODED ANIMALS

In the second series of experiments, I wanted to investigate the spontaneous and action currents on the cerebral cortex, and in this way to attempt to determine the localization of the functions of the cortex. These experiments did not differ much in their arrangement f m the ones already described, except for a few minor changes. For the pre- parations, I used nine rabbits and five dogs. However, the number of experiments is much larger than 14, because frequently, after the end of an experiment on one hemisphere, the &her hemisphere was also studied.

The experimental procedure was as follows : The animal was immobilized, if possible, and one side of the skull was

exposed, trephined, and the entire calvarium on that side was removed with the aid of bone forceps, so that the hemisphere on that side was completely exposed. During the entire pmcedure, precautions were taken not to injure the dura mater. Bleeding from the bones was checked by t e m p a r i l y applying pressure with a wad of &ton or by cauterization with a heated wire. After elevating the dura mater with a hook, it was cut into pieces, several of which were used to cover the bone, so as to prevent any injury to the brain from the sharp edge of the bone. Well moistened nonpolarizing electrodes, as previously described, were placed on two different points of the cortex; the procedure was otherwise the same as in the experiments with frogs. Of course the animals and electrodes could not be covered with a bell-jar; to prevent the brain from drying or cooling, the experiment was interrupted from time to time and the brain covered with warm, wet cotton, and the electrodes were moistened anew. In some cases, if the animal was restless, I did not place the clay electrodes directly on the brain but used pieces of yarn, saturated in 1010 NaC1,

DOCTORAL THESIS 31

which were hung on the clay and which did not change their position if the animal moved.

During the investigations of the current arising between two points on the mrtex, we observed its direction, its behavior for a time without stimulation, and then with stimulation of certain afferent nerves. For the latter, the optic nerve was stimulated with light, the auditory by making sounds, and the sensory nerves from various regions of the skin by means of an induction current. For stimulation of the eye with light, I used a burning magnesium r?bbon, which by means of a clock mechanism was fed from a suitably arranged device so that the point of light was station- ary and was reflected toward the eye with the aid of a mirror; the flame could be extinguished by stopping the mechanism.

Experiment 1

Large rabbit. After exposing of the right hemisphere, both electrodes were placed on the occipital part a t a distance of 6 mm from each other (Fig. 5 4 . A positive deflection of 57 mm followed, which indicates that the posterior electrode was positive and the anterior one negative.

The deflection was not constant but fluatuated such that it moved in a given direction for a few mm, or stopped for a shorter or longer period of time, only to move a few rnm forward or backward. Initially, I pre- sumed that the variation was caused by pulsation of the brain, which could change the contact between the surface of the brain and the electrodes; I soon became convinced, however, that the ascillations were not synchronized with the pulsations, and occurred spontaneously, completely independently of the latter.

Fig. 5.

The variations were as follows: 57, 47, 45, 47, 52, 50, 46, 41, 44, 40, 38, 32, 36, 33, 35, 30, 25, 28, 26, 31, 26, 21, 31, 41, 31, 36, 31, 21, 26.

32 A. BECK

When the magnesium was lighted before the left eye, which had previously been covered together with the right eye, the oscillations disappeared, and the deflection increased from 26 to 46.

After a 5-min interval, during which the elect&+ were changed: Defleotion: -36, -31, -36, -32, -26. Magnesium lighted: + 24 (negative variation, 50 mm). After covering the eye: $4, -4, -2, 4, 0, -5, -7, -3, -11. After stimulation of the hind leg with induction current: oscillation ceased, defle&ion did not change ( - 12). After cessation of stimulation, the oscillations reappeared :

-12, -8, -11, -9, -6.

After an interval of a few minutes, I placed the electrodes on the anterior parts of the hemisphere, 3 mm apart. (Fig. 5 m-m). After switch- ing the current off, i t became evident that the more anterior electrode was negative and the more postwior m e was positive; the ascillatims were much stronger than befme, and the current became progressively stronger.

Deflection: 38, 58, 53, 63, 68, 78, 73, 67, 73, 78, 90, 88, 101, 87, 90, 98, 82, 92, 97, 91, 94, 96, 100, 110, ... 132, 128, 132, etc.

Magnesium lighted: 132, oscillations quite insignificant; after light off, oscillations wturnecl. Stimulation of the hind leg increased the deflection up to 178, and the oscillations ceased.

I placed one electrode on the frontal part of the left hemisphere and the second on the occipital lobe, at a distance of 2 cm from the first (Fig. 6aa).

Fig. 6.

Deflection: 210, 216, 212, 218, 215, 228, 222, 226, 223, 229, 240, 243, 238, 236, 239, 243.

During stimulation of the right hind leg: 260, 261, 259.

DOCTORAL THESIS 33

After stimulation: 256, 260, 255, 268, 252, 248, 256, 244, 240, 243, 239, 248.

After magnesium was lighted in fmt of the right eye, oscillations ceased for a moment, but defleation did ncnt change from 248. Only after the cessation of sthulation did the deflection begin to decrease, amid oscillations : 245, 247, 242, 246, 235, 240, 229, 236, 228, 230, 224.

Experiment I1

Rabbit of medium size. Right hemisphere exposed and both electrodes placed ,on the occipital region, 3 mm a p d , parallel to the sagittal suture (Fig. 7aa); deflection was weak, 45 and slowly varying: 45, 40, 35, 40, 35, 31, 30, 27, 25.

After e x p i n g the eye to the burning magnesium, there were no changes in oscillations or deflection.

I moved the anterior electrode to the parietal region (Fig. 7bb);

Fig. 7.

Deflection: 103, 100, 102, 98, 93, 83, 80, 73, 71, 73, 77, 72, 71, 72.

After lighting rthe magnesium before the eye, the deflection increased without oscillations up to 104; after 'covering the eye it returned to 82 and the oscillation began: 82, 87, 83, 89, 80, 76, 82, 75, 78, 73. After a strcmg hand clap over the rabbit's ear, the oscillations ceased,

without change in the deflection. Stimul'atim of the left hind leg had the same effect. Then I placed both eledvodes m the parietal lobe close to the midline, 2 mm apart.

Deflection: 180, 185, 180, 185, 182. During stimulation of the hind leg: 140; after stimulation: 155, 151, 155, 150, 155:

3 - Acta Neurobiologiae Experimentalis

34 A. BECK

with ,repeat stimulation of the leg: 125; after stimulation: 130, 132, 125; hence the deflection did not return to the original value after stimulatim.

Experiment ZZZ

Rabbit. Right hemisphere. Both eleotrodes on the occipital lobe, 5 mm apart (Fig. 8ab).

Defleutim. 53, 42, 48, 46, 54, 43, 55, 47, 56, 45, 53. Magnesium lighted before the right eye; deflection decreased to 40, while the oscillations ceased. During hand clap over the rabbit's ear, the wdlatiom ceased, and the deflection did nat change.

Fig. 8.

I moved the anterior elednade 15 mm more anteriorly, to the frontal lobe (Fig. 8ac). A considerable deflection of 300; after a short time it decreased rapidly to 80; at that time I stimulated the anterior part of the &ex, as a result of which, there was a strong and rapid ddectton to the negative side, to -100; after the stimulation ceased, the deflection increased rhythmically, over 5 to 6 cm to 200. After repeat &mulation of the same location, the deflection moved to -160, then, after termination of the stimulation, returned to 180.

When I stimulated the posterior parts of the cortex, there was a rapid deflection to 445, which also diminishing rhythmically, returned to 220 after cessation of stimulation.

Experiment ZV

Rabbit. a) The first electrode was placed om the f m a l ldbe of the left hemi-

sphere, the second om the 'border of the parietal and f m t d regions (Fig. 90a).

DOCTORAL THESIS

Deflection: 90, 85, 90, 80, 75. During stimulation of the hind leg, oscillatims ceased; after stimula-

tion, 80, 75, 80, 85, 75. After repeat stimulation, the oscillation again ceased, but m t i n u e d anew after stimulation: 90, 80, 90, 80, 90. During stimulation of the eye with magnesium light, the deflection increased to 140 (Fig. 10).

Fig. 10.

b) Posterior electrode transferred to the occipital lobe.

Deflection: 70, 60, 65, 60. During stimulatim with mxgnesium light: 150. After stimulation: 130, 140, 135, 130, 120, 100, 95, 87, 80.

36 A. BECK

c) Finally, I shiffted the posterior electrode to the posterior limits of the occipital lobe (Fig. 90x).

Deflection: 230, 225, 232; d~uring stimulation with the magnesium light, it went to 330, then after terminatim of stimulation, it returned, eon- tinually oscillating, to 250. Right hemisphere. Electrodes placed on the occipital lobe, 6 m apart

(Fig. 1100).

Fig. 11.

Deflection: 85, 75, 80, etc.; during stimulation with magnesium light, 55; after stimulation, 85, 80, etc.; during repeat stimulation, 65; after stimulatim, 85. D u h g stimulation of the cortex in a location where the anterior eleatmde was fvruold to be negative, defledim: 275; whereas during stimulation of the cortex near the p t e r i o r electrode, - 30.

Finally, I began to naraoltize the animal with chloroform in order to see how the spontaneous oscillations behaved durimg narcosis. As soon as I started to give the chlomf~orm, the deflection, wMch read 140, began to change rapidly, going to the negative side as far as -330, where it began to oscillate, until the narcosis deepened. After the corneal reflex di5appeared, the oscillations also ceased completely anid I withdrew the chlomfom. After a little time, the oscibtSlolls begm to reappear, and at that time, examination of the corneal reflex indicated that the rabbit was beginning lo awaken from narcosis. I applied c m m h r m again, whereupon the oscillations became slower and weaker, amd finally they disappeaned completely.

Experiment V

Medium-sized dog. Curare injected into the femoral vein and artificial respiration imtituted. Left hemisphere exposed.

DOCTORAL THESIS 3 7

a) One of the eleotrodes was placed on the occipital lobe and the other on the parietal lobe, at a distance of 20 mm from the first (Fig. 12mr).

Deflection: 109, 115, 130, 120, 126, 132, 140. After sti,mulation of the eye with light, the defleation increased to 350; after covering the eye, it rapidly returned and even went over to the negative side, to - 30.

b) I moved the anterior electmde 10 mm pwkriorly (Fig. 1 2 ~ ) . I

Deflecti'cm: 81, 91, 96, 91, 86, 91, 86, 81, 76, 81. Duz'ing stimulation : 61. After stimulation: 71, 68, 73, 70.

c) I placed the anterior electrode on the temporal lobe, the posterior on the occipital lobe. Distance beitween electrodes, 18 mm (Fig. 1271,s).

Fig. 12.

Deflection: 45, 40, 50, 60, 80, 75, 70, 60, 50.

During stimulation with light, the deflectian increased to 230, but it did not decrease after cessatiroln of stimulation; ion the contrary, it went up to 350, where oscillations began. P d u c i n g a wund over the ear caused a slight deflediw of 2 mm to the pcsitive side; stimulation of the right foreleg or hinld leg was without effect.

38 A. BECK

Experiment VI

Four-week-old puppy.

Right hemisphere

a) One e leabde on the ocdpital M e , the other on the parietal lobe, at a distance of 12 mm (Fig. 13mr).

Fig. 13.

Deflection: 142, 145, 142, etc. While stimulating the eye with light: 195. After stimulation: 160; after repeat stimulation: 190.

b) The posterior electrode was placed on the [temporal lobe, the other, on the parietal lobe (Fig. 13ra).

Deflection: 200, 190, 205, 220, 210. The ear was tstiimulated With a l a d shout; deflection increased to 225; after the stimulation was over: 205; with repeat stimulation: 217 ; after stimulation: 205.

Left hemisphere

a) One electrode cm the parietal lobe, the second m the occipital lobe (Fig. 14x2).

Deflection, amid mcillations, to 230. Duiing stimulation with light: 190.

DOCTORAL THESIS

Fig. 14.

After stimulation: 200. During repeat sti~mulation: 210; then, despite cessation of stimulation, the deflection did not return to the original value.

b) I placed the anterior electrode on the temporal lobe, the other being left at the original site (Fig. 14zw).

Deflection, with oscillatims: 76.

Each sound stimulation resulted in a deflection of 4 to 6 mm to the positive side (hence, with each such stimulation, the rtempmzl region became more electmnegative than before); then, the deflection returned to normal after cessation of stimulation.

While stimulating with light, the deflectison returned to the negative side by 3 to 5 mm; after cessation 'of the stimulation, rthis change of deflection ceased. Consequently, the occipital lobe became electmnegative in this case.

I repeated the last experiment several times, always with the same result.

Experiment VZZ

Rabbit. Right hemisphere exposed.

a) One electrode placed on the frontal lobe, the second on the occipital lobe (Fig. 15ea). Interelectrode distance, 25 mm.

Deflection: 255, 250, 270, 285, 280, 275, 283, 280, 285, 270, 250, 260, 250, 265.

40 A. BECK

During stimulation with magnesium light the deflection increased to 310; after cessation of stimulation, however, it did not decrease a t all, but on the contrary, inweased steadily such th,at the scale went out of the field of vision.

b) The posterior eleatrodte (-) was moved 4 mm anteriorly and wme- what nearer the midline (Fig. 15ai).

Fig. 15.

Deflection: 70, 75, 80, 75, 65, 56, 55, 48, 52, 43, 37, 48, 40.

During stimulatian with light the deflection increased $0 72.

c) The posterior electrode was moved bo the parietal lobe, where it remained negative (Fig. 15ca).

Defleotion: 87, 80, 79, 74, 79, 69, 74, 79. During stimulation with light: 98. After stimulation: 96, 98, 95. During repeat stimulation : 138. After cessation of the latter: 72. While stimulating the hind leg, ithe deflection reversed itself, to -25;

then, after cessation of the stimulation, it returned only to zero and oscillated around that point.

Left hemisphere. Both eledrodes on the occipital lobe, 6 mm apart.

Deflection: 305, 310, 307, etc. After lighting the magnesium: 326. After removing stimulus: 323, 315, 325. The posterior electrode moved 3 mm posteriorly. Deflection: 75, 67, 82. During stimulation with magnesium light : 97. After covering $he eyes: 100, 90, 106, 96, 110, 95, 75,

70, 75, 65, 70. After repeat stimulation: 95.

DOCTORAL THESIS

Experiment V I I I

Curarized dog. Artificial respiration instituted.

a) On the left hemisphere m e electrode placed on the occipital lobe in region A' (Fig. 16); the second m e more anteriorly, at a distance of 12 m, on the anterior border of regim F (Fig. 16aoo).

Fig. 16.

Deflection: 70, 75, 78, 79, 76, 73, 80, 82, 80, 77, 80, 84, 89, 95.

Deflection during stimulation with light: 114. With the eyes covered: 113, 110, 105, 106, 105, 108, 110. Repeat stimulatim with light: 118. After the stimulation the deflection did not return.

b) Anterior electrode moved 8 mm toward the fmnM lobe (Fig. 16an).

Deflection: 180, 190,1195, 204, 210, 205, 195, 185. During stimulatim with light: 180.

After the stimulaQm: 155, 165, 155, 166, 162, 160, 169, 160.

c) The anterior electrode ( I - ) was applied to the temporal region at a distance of 15 rnrn from ;the posterior electrode (- ) (Fig. 16ax).

Deflection: 300, 304, 302, 305, 308. During stimulation with light: 3 15. After termination of stirnulartion: 310, 314, 308.

42 A. BECK

d) After an interval of a few minutes, the electrodes remained as in c, with the difference that the electrode on the temporal lobe was shifted as low as possible.

Deflection: 240, 245, 252, 255, 275, 279, 281. During stimulation with light the oscillations ceased, at 295. After the light was removed: 285, 282, 278, etc. While stimulating the ear with sound, the oscillations ceased without any change of the defleotim; stimulation of the hind leg had the same effect. During the stimulation of the eye with light, the deflection, which had already increased to 308, went ID 330, then, after the stimulation ended, did not further increase but oscillated: 330, 322, 318, 320, 324, etc.

e) One electrode placed on the parietal lobe, the other on the frontal lobe, 20 mm apart (Fig. 16st).

Deflection: 68, 64, 66, 75, 68. During stimulation of the cerebral cortex in the vicinity of the posterior electrode, deflection : 208 ; after stimulation : 48 ; during stimulation of the frontal lobe the deflection was -27; after stimulation, 4- 118. Stimulation of the right thigh: 118; after stimulation: 128, 123, 128. Stimulation of the thoracic skin on the right side: 113; after stirnula- tion, oscillations occur. During the stimulation of the forelimb, the deflectim deoreased to 96; the oscillations also decreased during stimulation with light: 198, 197, 199. The oscillations ceased during stimulation of the abdominal skin on the right side.

f ) Medulla oblongata and part of the spinal m d to the thilrd and fourth cervical vertebrae exposed. The bleeding was sufficiently signi- ficant to result in anemia, and, together with the effect s f the curare, in a very low blood pressure. One electrode was placed ioln the posterior part of the floor of the fourth ventricle, the secund one on the cervical spinal col.rd a t a distance d 12 mm from the first. A deflection on the positive side of 500-t0/o indicated that the medulla oiblmgata was electronegative in relation to the cord. After compensation to zem, the deflection increased on the positive side, so that I had to ccrmpsate to zero again, after whsicich a deflection with oscillations appeared: 54, 42, 40, 38, 50, 60, 65, 68, 60; longuer pause: 50; when artificial respiration was interrupted, the deflection increased to 70; artificial respiration con- tinued: 62, 48, 36; the oscillations ceased while the respiration remained.

DOCTORAL THESIS 43

At the end of this experiment, I should add that in this and the previous experiment, because of a lack of magnesium ribbon, I had to use the light of a candle, which I gathered with the aid of a lens and di~eded into the pupil. Apparently this light was not sufficient for the stimulation of the centers in the cortex.

Experiment ZX

Large non-curarized dog. Right cerebral hemisphere.

a) One of the electrodes on the visual area, A', the other on the motor area f o r the anterior extremity C (Fig. 17am). Distance between electrodes, 30 rnm.

Fig. 17.

Defleation: 49, 40, 43, 35, 39, 40, 45, 30. Left eye stimulated wi,th light : 18. After stimulation: 25, 30, 25, 40, 42, 45, 40. Stimulation of forelimb : 70. After stimulation: 55, 60, 55, 48.

b) After a longer pause, the posterior eleotrode was m v e d 5 mm more postetimly (Fig. 17m).

The deflection indicated elednmegative values of: 205, 195, 185, 188, 173, 175, 160, 165, 155, 151.

While stimulated with light: 172. After the stimulation: 155, 145, 156, 150, 157.

44 A. BECK

During stimulatim of the foreleg: 140. After stimulation: 145, 140. Stimulation of the cortex in the vicinity of the posterior electrode: 220. After stimulation, the deflection returned rhythmically to 152. During s.timulatim near the anterior electrode, deflectioln of 75. After stimulation: 159, 148, 156 (Fig. 18).

c) The posterior elect~ode placed on the temporal region G (Fig. 17mc).

Deflection: 173, 175, 182, 179, 183. Stimulation of the ear with a strong sound : 172. After cessation of stimulation: 155, 145, 135. S*timulath of the foreleg: 210; after stimulation: 150 with oscilla- t i m s . Stimulation of the cortex at C: 300; after stimulation: 90 with oscillations; stimulation of the cortex at G (the ear muscles contract), defledion: 80; after stimulation: 110, 123, 115.

DOCTORAL THESIS 45

d) Posterior electrode moved anteriorly to area E (Fig. 17mx).

Deflection: 75, 68, 72, etc. - Stimulation with sound: 115. After stimulation: 101, 108, 96, 98, 89. Start chloroform: 90, 96, 108, 102, 110; the animal is excited and the oscillations are very considerable. In deep n a r m i s rthe~e is a slow decrease in the deflecti'on to 55.

Experiment X

Rabbit. Left hemisphere. a) One electrode on the occipital lobe, the other on the frontal lobe

(Fig. 19c-m), separation: 15 mm.

Fig. 19.

Deflection: 479; mp.ansated to zero; oscillatims began: 0, + 5, 0, 4-4. Stimulated with magnesium light : - 3. After stimulatim: 0, + 2, 0. After stimulation of the right foreleg, during which the rabbit was very restless, the deflection suddenly moved to the negative side to -485. I removed the mpensa t ion and .the deflectim receded to - 150, where [there were mi8de rab le oscillatims; then, with repeat stimulation, the scale moved rapidly to the positive side to 240 and suddenly returned to - 355.

b) After the animal had calmed down, both eleatrodes were moved 2 mm posteriorly (Fig. 19od).

Deflection: 230; stimulatim with light: 255; after stimulatim: 240; during repeat stimulation: 285; after stimulation: 245, 240, 248, 236, 230. During stimulation of the foreleg, the rabbit was very restless; the

46 A. BECK

scale moved to the negative side to -300 and back to -28, -10, -25, -16.

Finally, I began the examination of the currents i n the medulla oblongata. After tracheotomy and instituting artificial re~pi~raticvn, I ex- p s e d the medulla and the greater part of ,the c e r v i d card, with relatively slight bleeding. One electrode was placed near the calamus scriptorius, the second on the cervical part of the cord, at a distance of 15 mm.

Deflection: 250, 240, 250, 242; while respiratory was interrupted, the deflection increased to 380; after restoration of the respiration, 320. Then 4he anterior electmde was moved 5 mm more anteriorly (on the floor of the fourth ventricle); the deflection was then 350. After interruption of respiration: 390.

Experiment XI

Rabbit. Left hemisphere. One electrode placed on the occipital lobe, the other on the frontal region (Fig. 19c-m).

Deflection: 390; compensated to 0.; oscillations: 0, 05, 010, 07, 010, 05, 07.

Stimulation with magnesium light, no change. Oscillations in general are rare. Stimulation of right hind leg; oscillations ceased.

The animal died during the experiment, probably from asphyxia- tion resulting from excessive pressure for securing the nose to the plat- form.

Experiment XI1

Dog. Left hemisphere.

a) One electrode placed on the fmntal lobe, the other on the occipital lobe (Fig. 20ao), 25 mm from the first.

Deflection: 178, 183, 189, 192, 198, 204, 193, 198, 203, 208, 200. Magnesium Lighted: 188-174. After stimulation: 166, 167, 178. Stimulation of the foreleg: 178 (oscillations ceased). After stimulation: 183, 187, 183, 188, 198. Suddenly deflection increased to 500+0/o; animal began to be restless.

b) Anterior electrode placed cm the temporal lobe (Fig. 200c);

Deflectian: 402; compensated to zero; oscillations began: -2, + 12, + 18, $27, +35, i-32.

DOCTORAL THESIS

Stimulated with magnesium light : 22. After stimulation: 24, 28, 27, 25, 28, 33, 29. Stimulation with sound: 36. After stimulation: 38, 35, 37, 32, 28, 33.

Fig. 20.

Experiment XI11

Rabbit. Left hemisphere. The first electrode placed on the occipital lobe and the second on the border betwen the frontal and the parietal regions (Fig. 210772). Initially, the deflection was -85, indicating that the posterior electrode was negative. Soon, however, the deflection began to move toward the loppolsite iside and, advancing rhythmically with oscillations of f m one to a few centimeters, increased to 500+O/o.

The deflections were as foows : -90...+165, 150 ... 250, 260, 250 ... 305, 295 ... 350, 330 ... 375, 355, 385, 390, 375...455...500+0/o. After compensation ,to zero, oscillations began.

48 A. BECK

During stimulation with light: - 17. After stimulation: +8, -2, -10, + 18 ....; the deflection increased again Co 500+0/o. After an interval lof a few minutes, the deflections were: 70, 61, 50, 60, 55, 45, 70, 65, 75, 66. During stimulation with magnesium light: 61. After stimulatilon: -20, - 25, - 20, - 30, - 20, - 25.

The posterior eledmde was moved anteriorly (Fig. 21am); interelectrode distance: 4 mm.

Deflection: 220, 218, 235, 245, 235. During stimulation with light : 250. After stimulation the deflection decreased, amid oscillatiolns, to 200. Both electrodes placed on the frontal lobe (Fig. 21nr). Deflections: 170, 165, 170, 158, 170, 168, 172. During sti,mulation with light : 160. After stimulation: 150, 145, 150, 142, 166, 148, 160, 156, 151.

Experiment XIV

I d f i e d the procedure in this experiment by placing two pairs of nm-polarizing electrodes on the hemispheres, which, with the aid of a swiitch, I m l d connect to Ithe galvamometer so that it indicated the deflection from one pair of locations on the cortex and, after moving the switch, for the other pair of locations. This modification was found to be exceedingly convenient.

One pair of the electiwdes was placed an the frontal lobe and on the parietal lobe, respwtively, at a distance of 8 mm (Fig. 22aa), the second pair (bbl), m the occipital lobe (separation: 6 mm).

a) The current led off from bb,.

Deflection: 226, 210, 213 ... 140, 118, 123, 103, 113, 93, 63, 67, 53, 67, 73, 63 (rabbit excited), 28, 23.

DOCTORAL THESIS

Stimulation with magnesium light: 38. After stimulation: 18.

b) Electrode b moved anteriorly and laterally.

Deflection: 25, 23, 25, 21, 26, 36, 30, 40, 35, 55, 45, 60. Magnesium is lighted: 40. After the stimulation, the deflection increased amid oscillations to 125. During stimulation with light: 105. After the stimulation, the deflection returned to 125. Repeat stimulation with light: 110. After stimulation: 120, 125, 123, 130. Stimulation with light: 120. After stimulation: 130, 139, 137, 145, 170. Stimulation of the hind leg: 175. After stimulation: 180, 187, 185.

c) The current led off from aal.

Deflection: 500f O/o; compensated to zero; ioscillations. Stimulation with magnesium without effect. Stimulating hhe hind 1,eg : - 18 ; oscillations ceased. After stimulation: -3, 0, -3, +9, 4-6. During repeat stimulation, the oscillations were 1 mm only and the deflection did not change.

d) I moved the switch so that the current came firom bbl (after removing the compensation).

Deflection: 180, 184, 179, 175, 180 ... 225, 221, 211, 220. During stimulation of the hind leg: 200; oscillations ceased.

e) Tracheotomy performed, and artificial respiration initiated; the medulla oblongata and a part of the cervical mrd were exposd; cme of the electmdes was placed on the calamus scriptorius, the second on the cord a t a distance of 12 mm from the first.

Deflection: 330; During cessation of artificial respiration: 335. During respiration: 330; during cessation of artificial respiration: 335. Duri,ng respiration: 331, 328, 330, 326.

4 - Acta Neurobiologlae Experimentalis

50 A. BECK

We must now examine the results of the experiments on the brain of warm-blooded animals, and several questions have to be answered. First: what is the nature of the current that constantly arises from the connection between two arbitrary p i n t s on the cerebral cortex and results in the deflection of the galvanometer? Referring to what I said a b u t the current in the brain and spinal cord & the frog, I will omit a detailed analysis of the reasons for the existence of the current, and we may boldly assert that it is a spontaneous active current, resulting from the difference in electrical potential arising from the fact that some of the centers are in a higher active state, while others are either completely at rest, or their aative state is significantly weaker than that of the first group. A specific proof of this assertim, it seems to me, would be super- fluous because I would be repeating everything I said previously about the resting and active current.

Similarly, we can easily explain the inconstancy of the spontaneous current and the continuous oscillations, which at one time appeared regularly around m e point of the deflection and at other times moved the deflection in one or the other direction. I mentioned before that they do not arise from changes in the cifrculation or f m pulsation of the brain during respiration; I only want to stress the fact that the oscillations were also not a consequence of changes in the contaat of the electrodes with the brain resulting from small, impercepti'ble movements of the animal, as might be supposed. This conjecture is without foundation, when we consider that the oscillaticms also appeared in the curarized animals. Most probably they are the expression of changes in the active state of the cerebral centers, changes which were manifest eibher as am excitation or as an inhibition. In the case of exc i t a th , the deflection increased when it arose in the vicinity of the negative pole, i.e., in centers which were already relatively more active, and decreased when centers in the region of the positive voltage became active. In the case of inhibitim, the initial deflection increased when the inhibition occurred in a region near the positive pole, and decreased during inhibition of centers with a heightened active state. Analogously, we find the changes arising from an increase of the active state in the phenomenon occurring from stimulation of the cerebral cortex, as occurred notably in Experiments I11 and IX. In those experiments, with each stimulation of the cerebral cortex in the region of the negative pole, the deflection increased, whereas it decreased whenever the vicinity of the positive pole was stimulated. We have a partial analogy to the changes produced in the current by inhibition in the effect of stimulation of the afferent nerves.

The results should now be considered in somewhat more detail. The

DOCTORAL THESIS 51

most striking are the phenomena resulting from the stimulation of the optic nerve.

Surveying the results from the experiments, we can observe that, whenever the eye was stimulated with light, there was a change in the initial deflection such as to indicate that the region of the cerebral cortex on which the posterior electrode rested became more eleatronegative, which means that the centers there went over into an active state. With each such stimulation the initial deflection increased if the direction of the current was such th& the positive pole was situated anteriorly to the negative pole, and decreased if the area toward the back were electro- positive. This phenomenon, however, was not always apparent to the same degree. In the first place, i t was different in dogs than in rabbits.

In dogs (Experiment VI and others), the change in the initial deflection was the stronger, the nearer to the posterior b r d e r of the occipital lobe one eledrode was placed, and the greater the distance between the electrodes. As we moved the posterior electrode toward the fmtal lobe, the change in the deflection resulting from stimulation by the magnesium light became progressively smaller, and disappeared altogether when both nonpolarizing electrodes were placed on the frontal lobe. Similarly, the resulting deflection was smaller when the distance between the two electrodes was decreased, even if they were both placed on the occipital lobe. However, in this case it did not disappear completely.

It is not difficult to explah this phenomenon. Most probably the stimulation of the eye with light activates the centers of the visual region of the cerebral cortex, and as a result an electronegative potential appears in that region of the cortex. If m e of the nunpolarizing electrodes is placed in the vicinity of the visual center itself and the second one sorne- what more anteriorly, then the greater the distance between the electrodes, the less iafluence this change has on the electrical potential on the anterior electrode. If the latter were placed outside the visual region altogether, then the difference in the potential between the two points from which the current is led off is the maximum, and acmrdingly the deflection during the stimulation of the eye with light is the most prominent. If both electrodes are situated near each other in the visual region, the electrical potential changes simultaneously in both but evidently not to the same degree, since the changes in the original deflection, though less, were nevertheless apparent.

With the rabbits, it was another matter. It is also true that an increase in distance between the electrodes resulted in an increase in the initial deflection and that the area with the posterior electrode was in contact became more and more electronegative during the stimulation of

52 A. BECK

the eye with light; however, this difference appeared even after b t h electrodes were moved appreciably forward, so that the posterior one was on the parietal lobe. This finding agrees with the experiments of Munk, who, as was previously mentioned, maintains that in the rabbit the visual region of the cerebral cortex is more extensive and extends further anteriorly than in the dog.

Apart from the increase or decrease in the initial deflection, yet another phenomenon occurred during stimulation of the eye with light, nemely, that during each stimulation, the previously described rhythmic oscillation ceased. However, this phenomenon was not the consequence only d stimulation by light, but appeared with any kind of stimulation of other afferent nerves, about which I shall say more subsequently.

The changes in the initial deflection during stimlulation of the auditory nerve were less distinct than those during the stimulation of the optic nerve. We know that the auditory area is situated in the temporal lobe of the cerebral cortex, mainly on its inferior surface. It is exceedingly difficult to reach that region with clay electrodes or with the thread, without Couching the base of the skull and the adjacent soft tissues. For this reason, I had to be satisfied with leading off the current from the lateral and superior parts of the temporal lobe. Even here, during stimulation of the auditory nerve, the current in mwt cases increased if the area was negative, and decreased if it was positive. To be sure, the deflection in m e or the other direction was not as marked as it was during stimulation of ofthe eye with light; however, i t did indicated that in any event the cerebral cortex of the temporal labe had become elect* negative and if the latter was already negative, that the ptentild of negative eleakicity had increased and hence that the centers situated there had became set into an active sbate.

Finally, during stimulation of various areas of the skin with induction currents, I obtained either an increase in the deflection or a negative variation from certain regiiorns of the cerebral cortex, especially hom the frontal and parietal lobes. From my experiments, however, I am not in a position to state exactly which parts of the cortex receive afferent nerves from which parts of the skin. Starting from the generally accepted theory that (in the dog) those parts of the cerebral cortex which we consider as psychomotor for certain regions of the body (extremities, chest) also contain centers receiving senlsory nerves from those regions, using blunt platinum electrodes and a weak induction current, I first very carefully stimulated the cerebral cortex in some of the experiments, evoking movements of, for example, an extremity, the head, an ear, by the stimulation of certain locations. I then applied an electrode to that point, in order to investigate the behavior of the current which was led

DOCTORAL THESIS 53

off from it during stimulation of the cutaneous nerves of the particular part of the body in which movements had been produced by the stimulation of the cortex. And indeed, the current led off from that point frequently resulted in a deflection (especially in Experiment IX), during stimulation of the skin of the corresponding part of the body, from which it can be concluded that an active state arose in the centers situated in the region of the cerebral cortex investigated.

If my assumption concerning the relationship of the deflection of the action current to the generation of the active state in certain centers is correct, that is to say, if the production of electronegative potential in an area of cortex really indicates that an active state arises in the centers situated there, then by direct stimulation of that spot an electronegative potential should also occur; in other words, a deflection should occur in the same direction as that which appears during stimulation of the afferent nerves the centers of which we expect to find at this location on the cortex

Such was my theoretical argument, and the experiments proved that it was correct. It is most evident in Experiment IXb (Fig. 18). If, during stimulation of the eye with light there was a positive deflection of 21 mm, whereas with direct stimulation of the cortex of the occipital lobe near the negative electrode a deflection of 80 mm in the same direct' I ion occux- red, does this not prove that during stimulation with light the same (occipital) region of the cerebral cortex underwent stimulation and went into an aotive state? Stimulation of the limb and the corresponding part of the cerebral cortex gave similar results, that is, both gave a deflection in the negative direction.

An important phenomenon, which I have mentioned previously, and which occurred in nearly all the experiments with stirnulaition of the cerebral cortex by one of the afferent nerves (especially during stimulation of the cutaneous nerves) was the arrest of the spontaneous oscillations of the action current. The explanation of this phenomenon if it is not accompanied by a coincident deflection is n& too easy. I would interpret it as an expression literally, we may say, of an arrest of the active state at a certain point and a suppression of the changes which occurred spontaneously in the active state. In a word, one can explain it by inhibition. It is nothing new tm us that the excitation of some centers causes inhibition of the active state of others. Our method con- firms this fact, and may even contribute to the explanation of the process of formation of the inhibition. We should add that the inhibition of the active state of some centers resulting from the excitation of others was incomplete, because in this case the initial deflection would have disappeared completely; it follows that a certain active state must have been

54 A. BECK

present in those centers and only the spontaneous changes of that active state were inhibited.

Speaking of the inhibition of the activity of centers, I should mention yet another kind of inhibition, namely that caused from chloroform narcosis. As we have seen, a t the onset of the chloroform narcosis, the deflections and the oscillations increased, which would correspond to the excitation appmriate for the beginning of narcosis; during the stage of deep anesthesia the oscillations ceased completely and the deflection continually decreased. This complete abolition of the oscillations can be explained by the cessation of all spontaneous changes in the active state of the nerve centers in the cortex, and (the decrease in the initial deflection can be ascribed to the narcosis d these centers.

Now, a few words about the respiratory centers in the medulla oblongata. In this respect, I have not done many experiments on warmblooded animals. In more numerous experiments on frogs, I did not confirm the results of Sechenov, in that I could not demonstrate the existence of respiratory centers in the medulla oblongata. In two experiments on warmblooded animals, the inte~.iruption of artificial respiration, with consequent excitation of the respiratory centers, resulted in an increase in the electronegative potential on the medulla oblongata.

It would be too audacious to wish to draw conclusions from so small a number of experiments on the medulla; I leave this to future investigations, when I will be able to simplify the experiments by introducing some modifications. In the form in which they have thus far been carried out, such modifications would be very difficult. One should also attribute to this difficulty that one or two experiments did not turn out well. However, I mention them without regard as to whether the results fmm them were positive or negative.

It is appropriate, finally, to appllaise the value of our method, and to answer first of all the question of whether the results of the experiments allow uls to hope that, by the method of determination of changes in the currents of the cerebral cortex, the localization of functions of various parts of the central nervous system can indeed be determined.

Anyone who has glanced at the experiments or at the tables showing their results has to respond affirmatively to this question. If in one or two experiments the results were negative or even contradicted the results of the majority of the experiments, this is not reason for dis- crediting the method itself. In the first place, the method, at any rate its

DOCTORAL THESIS 53

applicatilon to warmblooded animals, is still new, and consequently I could not await further improvements, which occur for every experimental method in proportion to its employment.

Secondly, the objective of the investigation itself is very difficult. For instance, during stimulation of the eye with light, which evokes an active state in the occipital regions, it could happen any number of times that, on the part of the cortex where the second electrode was situated, a negative potential would also appear as a result of the spontaneous appearance of an active state in the centers situated there. After all, the animal may simultaneously send an impulse to flee to the muscles, and precisely the stimulation of the eye with a bright light may in some cases evoke that impulse. And if m e electrode rests on the occipital lobe, the other on the motor part of the cerebral cortex for any of the extremities, then the deflection during stimulation with light will depend only on which active state produced a greater electmnegative voltage, whether the forrnati~an of the visual image in the sensory centers, or the impulse to movement in the motor centers. However, we may assume that first deflection, resulting from stimulation of the eye by the light, is an expression of an active state arising in the visual centers, and only then can the initilal deflection deorease or change to the opposite, as was actually the case in some of the experiments.

The difficulties which arise with the application of the method should not, however, deter us from its utilization because every other method will also have its own not insignificantly numerous negative aspects, and if in the future the difficulties can be overcome, or a t least all factors having an influence on the results c m be recognized so that they can be taken into account, the method of determination of localizatims from changes in currents occurring on the corebral cortex will be a very valuable one and possibly superior to all others, if only from the stand- point that with its applicatilon the active state of the nervous centers can be seen.

In closing, I would like to express my sincere gratitude to my honorable chief, Professor N. Cybulski, for encouragement in the present work, and for his valuable advice, of which he always gave unstintingly.

Bust of Adolf Beck sculpted by A. Karny, lost in the burning of Warszawa.

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