Vagal elicitation of respiratory-type and other unit responses in striopallidum of squirrel monkeys.

The putamen and globus pallidus were explored in awake, sitting squirrel monkeys while testing the effects of vagal volleys on the activity of isolated units. Triple shocks were applied to the left cervical vagus nerve every 4 sec. Special computer methods were developed for recording and analyzing data. As a control for adventitious extravagal somatic stimulation, units responsive to vagal volleys were also tested during shock-induced facial and cervical twitches. Under the given conditions, 30% of the units were responsive only to vagal volleys. The ratio of initially excited to initially inhibited units was about 2:3. The response latencies ranged from 6 to 200 msec, values indicative of both rapidly and slowly conducting, afferent pathways. The entrainment of respiration by vagal volleys revealed that 6% of the tested units gave a periodic discharge that appeared to correlate with the respiratory rhythm. This last result compares to that described and discussed in the following companion paper on basal limbic structures.