User:Rob Malenka/Proposed/Long-term depression

• Dr. Rob Malenka, Stanford University School of Medicine, Palo Alto, CA

• Dr. Mark Bear, M.I.T., Cambridge, MA, USA

This article is in preparation.

Long-term depression (LTD) is a weakening of a synapse after a short series of presynaptic action potentials or asynchronous presynaptic and postsynaptic activity. LTD is distinguished in homosynaptic LTD, heterosynaptic LTD and associative LTD.

Types of LTD

• homosynaptic LTD: LTD is confined to the synapse where the short series of action potentials arrived.
• heterosynaptic LTD: LTD affects also other synapses of the respective cell.
• associative LTD: Asynchronous pre- and postsynaptic increase of intracellular calcium causes LTD.

Occurrences of LTD

• Cerebellum
  • Purkinje cells: Purkinje cells receive unspecific excitatory input from parallel fibers. But each purkinje cell receives a synapse from a single climbing fiber. Activation of a climbing fiber results in a reduction of the excitability of the according Purkinje cell. This LTD is related with the accomodation of the vestibo-ocular reflex to optical conditions.
• Hippocampus