Synchronizing Mechanisms of the Thalamus

The question of the source of various forms of rhythmic activity is important for understanding the intracentral relationships as well as the functional role of brain structures where this type of activity is observed. Furthermore, elucidating the mechanisms of synchronizing activity may be a crucial factor in understanding fundamental brain states such as sleep and wakefulness, arousal response, orienting reflex, etc. The fact that spindle-shaped and "bursting" barbiturate activity at a frequency of 8-12 Hz occurs synchronously in the cerebral cortex and nonspecific thalamic nuclei has led to the suggestion that the primary source of their generation is the thalamus (nonspecific nuclei). This assumption was strengthened after it was established that removal of the cortex does not suppress "bursting" activity in the thalamus in both unanesthetized animals and under barbiturate anesthesia. Similar data were obtained from preparations of the "isolated thalamus."