PLASTICITY OF THE OLIVOCEREBELLAR PATHWAY

The adult olivocerebellar axons and their terminal arbours, the climbi ng fibres, are capable of remarkable structural plasticity, regulated through their interaction with Purkinje cells. When these cells are de leted, terminal climbing fibre branches retract. In contrast, there is a vigorous outgrowth of entire terminal arbours when extra postsynapt ic neurones are available. The new connections lead to a functional, h ighly specific pattern of innervation at the single Purkinje cell leve l and are topographically organized according to the principles of the original projection map. A reversible climbing fibre retraction occur s following depression of electrical activity of the cerebellar cortex . These remarkable plastic properties, together with the fact that the se neurones express several growth-associated genes constitutively, su ggest that the climbing fibre synapses might be adjusted dynamically t o participate in physiological plasticity.