Map projection rewiring in the adult cerebellum after lesions

摘要

Functional recovery following a lesion in the brain depends on the ability of the injured neurones to regrow their axons up to the target and to restore the original projection map. In this review we show that these two important processes occur in the rat olivocerebellar pathway both during the developmental stage and in the mature brain. Axotomised olivocerebellar neurones regenerated into a graft of freshly dissociated Schwann cells and some of them reached previously deafferented Purkinje cells. To study the specificity of the newly formed connections we have adopted three experimental protocols aimed at seeing the specificity of reinnervation into sagittally oriented Purkinje cell bands identified by zebrin II antibodies. First, during postnatal development, following unilateral pedunculotomy, fibres from the uninjured pathway cross the cerebellar midline to reinnervate symmetrical Purkinje cell bands. Second, by grafting embryonic Purkinje cells in the mature cerebellum, olivocerebellar fibres reached the specific neurochemically defined Purkinje cell compartments into the graft. Third, in the mature cerebellum, following a subtotal inferior olive lesion, collateral sprouting of the surviving climbing fibres was confined into the proper cortical compartment. These results show that olivocerebellar fibres have a strong intrinsic capability to regrow their axons and that this growth is not randomly oriented, but it is regulated by selective interactions between distinct subsets of inferior olive axons and target neurones.