Plasticity in cerebellar tactile maps in the adult rat

We previously demonstrated that the fractured tactile cerebellar map within the crus IIa folia of the cerebellar hemispheres reorganizes after deaffer entation of the upper lip in neonatal rats (postnatal day [PND] 1-30). The present study examined the capacity of this map to reorganize after deaffer entation in adults and animals late in development (PND 30-89). Several mon ths after cauterization of the infraorbital branch of the trigeminal nerve, the tactile map in the granule cell layer of crus IIa reorganized, with re presentations of intact structures expanding into the denervated area. The pattern of reorganization was similar to reorganization after neonatal lesi ons in that (1) all representations were from perioral structures, (2) the reorganized map maintained a fractured somatotopy, and (3) the denervated a rea was predominantly and consistently invaded by the upper incisor represe ntation. We conclude that the spatial pattern of reorganization is essentia lly the same regardless of the age of deafferentation. However, we also obs erved developmental differences in reorganization. First, more areas of cru s IIa were nonresponsive in animals lesioned later in development (PND 30-8 9). Second, we found a surprising degree of variability in the pattern of t actilely evoked cerebellar field potentials of PND 30-40 animals compared w ith neonates and adults, suggesting that this time period differs from othe r stages. The pattern of evoked potentials reflects the two primary inputs to the map. Our data show that, although both afferent pathways are capable of reorganization throughout development, their relative contribution to t he map appears to differ, depending on the age at which lesion (C) 1999 Wil ey-Liss, Inc.