Evidence for Excitatory Input to Ventral Spinocerebellar Tract Neurons Mediated by Motoneuron Collaterals

This study evaluated the hypothesis that motoneuron collaterals modulate the excitability of ventral spinocerebellar tract neurons. In acute cats, 128 ventral cerebellar tract cells were studied extracellularly to determine the effects of ventral root stimuli. The majority of the cells responded to ventral root stimulation with either short or long latency increases in spike discharge. In many cells with sufficient spontaneous activity ventral root stimulation also evoked a long lasting reduction in activity. In preparations with the dorsal root ganglion removed VSCT neurons had similar response properties. In some cells contralateral ventral root stimulation also evoked excitatory responses. These findings indicate the VSCT can provide the cerebellum with information regarding activity in the final output neurons of the motor system, the alpha motoneurons.