Electrical Currents of the Brain

ELECTRICAL currents, graphically recording these currents—modern knowledge about the structural features of the cerebral cortex, the so-called architectonics of the brain, is of enormous importance. If, until very recently, all researchers could speak

Fig. 7. Diagram of an amplification device for recording bioelectric phenomena in the cerebral cortex.

about the electrical potentials of the brain when leading off currents from the "two poles of the brain" or two "areas" of the brain, then modern knowledge about the architectonics of the brain allows us to approach much closer to an understanding of the connections and relationships of these bioelectric currents with individual architectonic fields of the cortex.

Fig. 8. Intrinsic currents of individual fields of the rabbit cerebral cortex: 1-regio motorica (area agranularis); 2-area striata (visual zone); 3-auditory zone; 4-regio parietalis; 5-regio retrosplenialis granularis; 6-bulbus olfactorius.

of the brain, which opens up new possibilities for penetrating the dark areas of brain function. Work in this direction has been started in recent years at the German Brain Institute. At the present time, the Moscow Brain Institute has not only mastered the corresponding apparatus and methodology but has also achieved very important results in this field. Sarkisov and Livanov managed to show that individual architectonic fields, which were spoken of above, such as, for example, the motor, visual, and auditory, have their own characteristic electrical currents for a given area, the so-called intrinsic currents of the cortex (Fig. 8). Furthermore, the studies of these authors showed that with corresponding external stimuli, these intrinsic currents produce changes. Thus, for example, if one leads off the intrinsic currents from the visual area of the cerebral cortex and immediately applies an external stimulus to the eye with light, then at the moment of applying the stimulus, a change in the curves occurs immediately, which is graphically recorded on an automatically operating camera (Fig. 9). Even more striking is the fact that an external stimulus applied to the visual area of the cortex is not indifferent to the neighboring field, since the intrinsic curves of this neighboring field significantly decrease in amplitude (Fig. 10). This fact is of extremely great importance in understanding the mechanisms of the work of the cerebral cortex, in understanding the relationships of individual areas of the cortex in one act or another. If until now we could, on the basis of the fundamental works of the school of I. P. Pavlov, as well as the works of A. A. Ukhtomsky and others, speak about a whole series of important propositions regarding the basic mechanisms of the activity of the cerebral hemispheres, then undoubtedly the method of capturing and recording bioelectric currents provides some objective expression of these mechanisms. Along with these data, it is important to study the nature of the bioelectric phenomena of the cerebral cortex itself—deriving a number of regularities about the character of the obtained curves, about their correlations with individual areas of the cerebral cortex, etc. Fig. 10. Intrinsic currents (regio motorica area agranularis) decrease upon stimulation of the neighboring field ('); intrinsic currents of regio parietalis change (decrease) upon stimulation of the neighboring field area striata (2). Kornmüller noted the position that those areas of the cerebral cortex which are characterized by the presence of small cells (in particular the visual area of the cortex, area striata) produce curves with significantly expressed amplitudes and, conversely, areas of the cerebral cortex characterized by the absence of small cells and a richness of large cellular elements produce curves with small amplitudes. The experiments of Sarkisov and Livanov fully confirm this position. In addition to this, regarding the question of studying the curves of bioelectric currents in the sense of revealing a number of regularities, special work has been conducted in the laboratory of the Brain Institute (M. N. Livanov), which allowed, on the basis of mathematical analysis of these curves according to the method of analysis of aperiodic curves of N. A. Bernstein, to arrive at interesting assumptions about the character of the curves of individual areas, their nature, and regularity. Now there is already the possibility of delving even deeper into the nature of the obtained curves of bioelectric currents, not only in the sense of their connection with individual architectonic fields of the cerebral cortex but also in the sense of the relationship of individual layers of the cortex in the manifestation of these bioelectric currents—a fact of enormous importance for clarifying the mechanisms of the work of the cortex as a whole and its various areas individually. Finally, the latest achievements in these studies consist in the fact that if in the first period of work bioelectric currents were obtained directly from the brain, i.e., by opening the skull of the experimental animal, now it is possible to obtain bioelectric currents without opening the skull, i.e., through the bone tissue (Fig. 11). True, the currents obtained through the bone tissue, in contrast to the currents obtained directly from the brain, are not as strongly expressed, but here the question can only be about further improvement of the technique and methodology of research. These data themselves already open the way to more important research—to the study of bioelectric currents in humans. The works of the Viennese scientist Berger and works of the same character started at the Moscow Brain Institute, as well as the works of Adrian that have appeared recently, show that a new, extremely important path to the study of the human brain is opening up.