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Role of Olivocerebellar System in Learning Dependent Timing Of Movements.

Chris I. De Zeeuw

Department of Neuroscience, Rotterdam , The Netherlands

The olivocerebellar system is organised in separate modules. Each module controls the timing and amplitude of particular movement components about a particular axis in space. Dynamic regulation of electrotonic coupling between inferior olivary neurons, which provide the climbing fibers to Purkinje cells in the cerebellar cortex, has been proposed as one of the major mechanisms underlying the control of the timing of movements, while the induction of long term depression (LTD) at the parallel fiber to Purkinje cell synapse may be one of the major mechanisms underlying adaptation of the amplitude of movements. We have created and/or tested several mouse mutants in which electrotonic coupling between olivary neurons or induction of cerebellar LTD is disturbed. By subjecting these mouse models to an eyeblink conditioning paradigm we show that both cellular phenomena are essential for learning dependent timing; a lack of olivary coupling results in random timing, while a suboptimal level of LTD induction at the parallel fiber - Purkinje cell synapse results in fixed but inappropriate timing as well as a reduced amplitude of conditioned responses.