[Effect of electrical stimulation of hyperstriatum on nucleus dorsalis intermedius ventralis anterior thalami somatosensory units in pigeon].

Discharges of 88 somatosensory units in the nucleus dorsalis intermedius ventralis anterior thalami (DIVA) in response to afferent impulses of radial nerve on 55 urethane anesthetized pigeons were recorded and analysed. Among the 88 units, part of them also responded to the stimulation of sciatic nerve. Following electrical stimulation of somatic projecting area of hyperstriatum, the spontaneous discharges and the responses of DIVA somatosensory units to radial inputs were obviously inhibited and the degree of inhibition was linearly correlated with the frequency and intensity of stimulation. The inhibitory effect on the responses to radial inputs may cause an increase in latency and a decrease in number of spikes. These results indicate that the DIVA certainly belongs to somatosensory system, and the somatic projecting area of hyperstriatum has a descending inhibitory effect on the DIVA somatosensory units. The hyperstriatum may thus exert feedback control over its sensory inputs through descending inhibition. It appears that the functional connection between the highest region of central nervous system and thalamus in avian is similar to that of mammal.