In the cerebellum,long-term depression(LTD)of synaptic transmission from parallel fiber(PF)to Purkinje cell(PC)has been considered to be a core mechanism for motor learning(LTD hypothesis of motor learning).As a molecular mechanism underlying LTD,it has been shown that coincidental activation of PFs and climbing fiber(CF)induces a sharp increase in [Ca2+]in,which activates PKCα.