Fastigial nucleus modulation of medullary parasolitary neurons

Input from the cerebellar fastigial nuclei to neurons at the lateral margin of the nuclei of the solitary tract, particularly to the area identified as the nucleus parasolitarius was investigated in acutely prepared, anesthetized dogs. Fastigial nucleus stimulation led to short latency excitation of nucleus parasolitarius units often followed by prolonged inhibition of spontaneous activity. Excitation from deep skeletal muscle afferents, converged on 25% of the spontaneously active units excited from the fastigial nuclei; these afferents originated primarily from the ipsilateral forelimb muscles. This study provides electrophysiological evidence for fastigial modulation of neurons previously demonstrated autoradiographically to receive presumed monosynaptic fastigial nucleus efferents. The convergence of forelimb muscle afferent information tentatively identified as being from Group Ia or Group II pressure stretch receptors suggests that the nucleus parasolitarius may be an integrative area for cerebellar, sensorimotor and/or autonomic information.