ELECTROENCEPHALOGRAPHICAL STUDY OF HUMAN THALAMUS

Summary The author observed reaction upon electrical stimulation in various portions of the thalamus of 120 clinical cases which were given surgical operations on the thalamus for the therapeutic purpose and arranged a series of examinations centering around the thalamic potentials, including its relation tc the cortical activity and effects upon the latter under inifluences of various factors such as narcosis and others. The thalamic potentials depend upon the psychotic condition at the time of recording just like the cortical activity, though the former is always pretty poor in fast component and composed of alpha wave of 8 to 12 c/sec., having no marked regional characters within the thalamus. Under the awaken but unconscious state, the bask pattern of the thalamic potentials, i. e. alpha wave, is duplicated by small fast wave, becoming much irregular with the time accompanied at the same time with the intrathalamic differences. The synchronization between the thalamic and cortical activities becomes remarkable as the function of the brain goés decreased. Narcotics working on the brain stem give a marked effect on the thalamic‐ potentials always to make them slower. Namely, in the beginning stadium of narcosis. the thalamus locks of fast wave which is already seen in the cortex; on the other hand, large slow potentials are recorded in the thalamus still alter the diminution of the cortical activity In narcosis. Convulsion and small fit caused by electrical stimulation of the thalamus exhibit remarkable changes in the thalamic potentials, thereby, the thalamic activity coincides with the cortical one in wave pattern as well as process. what type the fit may be. Further. a typical wave pattern of petit mal of 3 c/sec. was demonstrated in one of the cases of petit mal epilepsis which happened to exhibit a small fit during record‐taking of the thalamic potentials. In the lowering of the cerebral function caused by repetion of electroschock (ESD), the thalamic activity was found remarkably to slow down just alike the cortical one and having slow wave of 1 to 3 c sec. A marked synchronization with the cortical activity was noticed also in this case. Moreover, ESD cases do not exhibit the so‐called barbiturate fast wave in narcosis. The recruiting response caused by continued electrical stimulation of the thalamus which was evidenced hitherto only on animals was found also producible In man, if the condition is regulated properly. This reaction is considered to suggest something on the sleep mechanism of thalamic origins because it goes always precedent to the sleep.