Activity of neurons of cerebellar nuclei during fictitious scratch reflex in cat. I. Fastigial nucleus.

The activity of neurons located in the rostral part of the fastigial nucleus was recorded during the fictitious scratch reflex in thalamic cats immobilized with Flaxedil. The activity of most of the neurons was rhythmically modulated in relation to the scratch cycle: they generated bursts of impulses separated by periods of silence or, in a few cases, by periods of reduced activity. The discharge pattern of neurons was usually the same during both ipsilateral and contralateral scratch reflex: in both cases their maximum activity could be observed in the extensor phase of the scratch cycle. Rhythmical modulation of fastigial neurons is determined by signals coming from the central spinal mechanism, generating rhythmical oscillations, via the ventral spinocerebellar tract (VSCT) and the spinoreticulo-cerebellar pathway (SRCP). Results of separate transections of these pathways suggest that the SRCP determines the periodical excitationm of fastigial neurons and the VSCT their periodical inhibition.