Thalamic and cerebellar influence on single units of the cat cuneate nucleus

Abstract

The activity of single units was extracellularly recorded from cuneate nucleus in cats anesthetized with Nembutal. Stimulation by trains of four impulses, 300/sec, of nonspecific thalamic nuclei and cerebellar fastigial nuclei could modify the spontaneous and evoked activity of both interneurons and relay cells. The peripherally evoked and spontaneous activity of CTR neurons were depressed for 150–200 msec after thalamic and cerebellar stimuli in, respectively, 40 and 30% of the cells while the antidromic lemniscal potential was never affected by these stimuli. Both excitatory and inhibitory effects were detected on cuneate interneurons after thalamic and cerebellar stimulations. The nonspecific thalamic nuclei stimulation evoked potentials in 70% of the interneurons and the fastigial nuclei in 40%. Most of the analyzed interneurons showed a characteristic convergence of peripheral and central (cortical, thalamic, reticular, cerebellar) excitatory and inhibitory effects. In interaction experiments both cerebellar and thalamic (conditioning) stimuli could inhibit the activity evoked by different test (cortical, reticular, and peripheral nerves) stimuli, at intervals of 10–200 msec. Inhibitory effects between cerebellar and thalamic stimulations were also observed. These results show that both nonspecific thalamus and cerebellum presynaptically control the sensory cuneate nucleus transmission through the effect exerted on the cuneate interneurons. This effect is considered to be mediated by the brain stem reticular formation.