Effects of volleys in cortico-spinal tract fibres on ventral spino-cerebellar tract cells in the cat.

Both excitation and inhibition has been found in cells of origin of the ventral spino-cerebellar tract (VSCT) to be evoked by volleys in cortico-spinal fibres. The earliest EPSPs and IPSPs had features of disynaptically evoked postsynaptic potentials; these were, however, found only in a small proportion of cells and polysynaptic EPSPs and IPSPs were dominating . Postsynaptic potentials evoked in VSCT cells from primary afferents were effectively facilitated by cortico-spinal volleys. The cortico-spinal effects on VSCT cells may thus well be mediated by the same interneurones which mediate their excitation or inhibition from the periphery and which could evoke similar postsynaptic potentials in motoneurones. Generally all the observation are in keeping with the hypothesis (Lundberg 1971) that VSCT cells monitor transmission through interneurones interposed in various reflex paths to motoneurones.