Both the depression and the potentiation of synaptic transmission between a cerebellar granule cell and a Purkinje cell, which are considered the cellular basis of motor learning, were established in a simple culture preparation. The repetitive stimulation of both a granule cell and an inferior-olivary neuron depressed the synaptic transmission, and the repetitive stimulation of only a granule cell potentiated the transmission. Thus, a simple model system, where detailed analysis of molecular and cellular mechanisms of synaptic plasticities can be performed, has been established.