CORRELATED ACTIVITY IN THE SPINOCEREBELLUM IS RELATED TO SPINAL TIMING GENERATORS

Encoding of information by neuronal populations implies a correlation of neural activity across cells. Therefore recent evidence for correla ted activity in different parts of the nervous system has been interpr eted as a possible mechanism for functional coupling or coordinated in formation processing. We compared the activity in the messy fiber proj ection, the dorsal spinocerebellar tract (DSCT) with the responses of Purkinje cells in the spinocerebellum for evidence of correlated activ ity. A principal component analysis of post-stimulus spike activity re vealed temporal patterns of correlated Purkinje cell activity in all p arts of the spinocerebellum evoked by rapid, small amplitude passive j oint rotations in anesthetized cats. The same basic temporal patterns were induced in DSCT neurons by joint rotations and also by direct ner ve stimulation, showing that the patterning resulted from centrally ge nerated rather than peripheral timing. The evidence implies that spina l timing generators, activated by mechanical stimulation of the ipsila teral hindlimb, transmit temporally correlated activity to the cerebel lum via spinocerebellar pathways resulting in a coherent modulation of activity in diverse areas of the cerebellar cortex thereby providing the basis for a functional coupling.