1967 年 19 巻 4 号 p. 269-289
The direct and indirect effects of the stimulus given to the thalamus were electrophysiologically studied by using rabbits.
Describing the result of the experiment from the direct effect of stimulus, an appearance of a movement accompanied by a muscular discharge evoked thereby was noticed, in addition to a recruiting response and arousal reaction as the result of such an electrical stimulation of the thalamus.
It was clarified that this muscular discharge is due to an excitation of the nervous system, which is different from the recruiting response or arousal reaction, and that such a phenomenon may be evoked both by 100 c/s stimulus and by 8 c/s stimulus.
Then, regarding the effect of an indirect stimulus given to the efferent pathway, the evoked muscular discharge in the fore and hind limbs due to the stimulation given to the cerebral cortex and the sciatic nerve was examined.
In this muscular discharge, the thalamus was seen to indicate both facilitating and inhibiting effects similarly to 8 c/s stimulus and to 100 c/s stimulus.
A histological examination revealed that the region exerting a facilitating influence exists in the central part of nucl. ventralis anterior, and that the inhibiting tissue surrounds it. Furthemore, it was known that as to nucl. centrum medianum, on the contrary, the inhibiting system exists in the central part and the facilitating tissue is located in the outer peripheral part.
In regard to the influence exerted by the stimuli given to the thalamus on the afferent evoked potential revealed by applying an average response computer, it was seen that the inhibiting effect was observed in all cases under 8 c/s stimulus and in almost all cases under 100 c/s stimulus.
In the light of such experimental results about the afferent evoked potential, it was understood that, independently of the appearance of the shape of brain wave, the indirect facilitating or inhibiting effect may be influenced by the respective regional characteristics, in other words, that the inhibiting effect may appear in a region where more inhibitory tissues exist, and on the contrary in a region having more facilitating tissues, the facilitating effect may appear more prominently.