Bistable switches for synaptic plasticity.

A persistent decrease in synaptic efficacy, called long-term depression (LTD), of the parallel fiber-Purkinje cell synapse is thought to underlie some forms of learning and memory in the cerebellum. Simulation studies predicted that mitogen-activated protein kinase and protein kinase C would mutually activate each other and make a bistable positive feedback loop, thereby providing a molecular basis for LTD. This claim stimulated experimenters to successfully demonstrate the feedback loop and its pivotal role in cerebellar LTD.