The isochronic band hypothesis and climbing fibre regulation of motricity:an experimental study

The dynamic organization of the olivocerebellar afferent input to Purkinje cells was examined in rat cerebellar cortex. The distribution of synchronou s Purkinje cell complex spike activity was characterized, bilaterally, util izing multiple electrode recordings in crus IIa folium under ketamine anaes thesia. The results confirmed the existence of rostrocaudal complex spike i sochronicity bands with a mediolateral width of 500 mum. For a given band, no finer spatial submicrostructures could be discerned at a first-order app roximation (two-dimensional projection). Closer analysis determined that is ochronicity between bands is not continuous in space but demonstrates discr ete discontinuities at the mediolateral boundaries. Principal component mul tivariate analysis revealed that the first principal component of the spati o-temporal variance is synchronicity along the rostrocaudal band with a dec reased level of coupling in the mediolateral direction at the band boundary . Furthermore, this discrete banding isochronicity is organized by the dist ribution of feedback inhibition from the cerebellar nuclei on to the inferi or olive nucleus. The usual multiple band structure can be dynamically alte red to a single wide-band dynamic architecture, or to other patterns of act ivity, as may be required by movement coordination.