Neurons in the Inferior Olive Asynchronous Release of G

sthat play a central role in motor learning. IO neurons provide an instructive signal for long-term depression of granule cell to Pur-kinje cell synapses that is thought to be necessary for correcting inappropriate motor output (Ito, 2001; Raymond et al., 1996; Thompson, 2005). Gap-junction coupling between IO neurons promotes synchronous firing in a manner that is thought to allow coordination of cerebellar learning across muscle groups. Inhibi-tion from theDCNregulates theactivityof IOneuronsandcontrols the extent of synchronous firing of IO cells (Lang et al., 1996). Despite the importance of this synapse to motor control, nothing was known about the properties of the DCN to IO synapse. Here we describe the DCN to IO synapse and find that the properties of this synapse are highly unusual. Most synapses et al., 1987; Rowland and Jaeger, 2005; Thach, 1970), inhibition is powerful as a result of both facilitation and a highly prolonged time course of release. What distinguishes the DCN to IO synapses described here is the extreme domination of asynchro nous release at all frequencies. The slowly developing, sustained DCN to IO inhibition appears to be specialized to provide a strong, continuous suppression of the instructive signa provided by climbing fibers and to regulate the synchronou firing of IO neurons