How cerebral and cerebellar plasticities may cooperate during arm reaching movement learning:: A neural network model

Learning process results from synaptic plasticities that Occur in various sites of the brain. For arm reaching movement, three sites have been particularly Studied: the cortico-cortical synapses of the cerebral cortex, the parallel fibre-Purkinje cell synapses of the cerebellar cortex and the cerebello-thalamo-cortical pathway. We intended to understand how these three adaptive processes cooperate for optimal performance. A neural network model was developed based on two main prerequisites: the columnar organisation of the cerebral cortex and the Marr-Albus-Ito theory of cerebellar learning. The adaptive rules incorporated in the model simulate the synaptic plasticities observed at the three sites. The model analytically demonstrates that 1) the adaptive processes that take place in different sites of the cerebral cortex and the cerebellum do not interfere but complement. each other during learning of arm reaching movement, and 2) any linear combination of the cerebral motor commands may generate olivary signals able to drive the cerebellar learning processes.