[Functional significance of the round nuclei of the thalamus in formation of the sleep--wakefulness cycle].

In chicken with bilaterally lesioned thalamic rotundus nuclei, cholinomimetic effect of arecolin upon duration of each stage of the wakefulness--sleep cycle, was studied. No prolongation of the paradoxical sleep characteristic of the animals with intact thalamic nuclei, was observed in experimental chicken. The latter developed mainly a king of cataleptic immobilization duration of which was enhanced by arecolin administration. The thalamic rotundus nucleus was concluded to play an essential role in the mechanisms for regulation of the wakefulness--sleep cycle in birds.