Evoked potentials in the hypothalamus

Abstract

The distribution and some properties of the evoked potentials in the hypothalamus from stimulation of the sciatic nerve were investigated in 60 cats. In the posterior and lateral hypothalamus biphasic positive-negative responses of 7–10 msec. latency were found, while in the anterior and medial hypothalamus the stimuli evoked monophasic negative waves of 20–35 msec. latency. The threshold of activation of the hypothalamic potentials corresponded to the upper range of activation of group A fibers in the sciatic nerve. The hypothalamic evoked potentials had a very prolonged recovery time on double stimulation, were sensitive to pentobarbital even to a greater degree than the evoked potentials in the midbrain reticular formation, and were abolished by high frequency stimulation of the midbrain reticular formation. The long latency potentials in the hypothalamus were similar to those evoked in the midbrain reticular formation, while the short latency potentials had properties similar to those of the lemniscal potentials. This fact suggested that the short latency potentials signaled the arrival of impulses from lemniscal collaterals.