Long-term depression (LTD) is a weakening of a synapse that lasts from hours to days. It results from either strong synaptic stimulation (as in the cerebellum) or to persistent weak synaptic stimulation (as in the hippocampus). Compare to long-term potentiation.
LTD occur when Schaffer collaterals are stimulated at low frequencies, approximately 1 Hz, for long periods (10-15 minutes).
LTD is thought to result from changes in postsynaptic receptor density, although changes in presynaptic release may also play a role.
Cerebellar LTD has been hypothesized to be important for motor learning. However, it is likely that other plasticity mechanisms play a role as well.