抄録
The vestibuloocular reflex (VOR) stabilizes vision during head turn by counter-rotating the eyes in the orbit. Its gain (eye velocity/head velocity) can be modified by visual-vestibular mismatch, but following cerebellar inactivation, the gain cannot be further modified. Thus, the VOR has been a model system to study potential cerebellar roles in motor learning. The cerebellum may have different roles in acute versus chronic VOR motor learning, because cerebellar inactivation entirely eliminates any acutely learned component, but it only partially eliminates the memory of long-term gain change, suggesting multiple loci for the chronic memory. To pinpoint these, a series of experiments in which activities of cerebellar Purkinje cells (PCs) and their target neurons in dorsal Y group (YNs) were recorded before and after chronic VOR motor learning. The sensitivities of PCs to both vestibular (V) and efference copy (E) signals changed with learning, YNs changed their sensitivities to V modalities, and these changes are asymmetric for gain increase and decrease. Computational modeling revealed significant changes in 1) V pathway to cerebellar flocculus (FL), 2) direct V pathway to YNs after gain increase, and in 3) E pathway to FL, 4) direct V pathway to YNs, 5) pathway from PCs to YNs, and 6) V pathway excluding those through FL and YNs after gain decrease. The results suggest involvement of several loci in chronic learning and different neuronal mechanisms for gain increase and decrease. [J Physiol Sci. 2006;56 Suppl:S43]
