Studying Signal Transduction in Single

Many forms of synaptic plasticity are triggered by biochemical signaling that occurs in small postsynaptic compartments called dendritic spines, each of which typically houses the postsynaptic terminal associated with a single glutamatergic synapse. Recent advances in optical techniques allow investigators to monitor biochemical signaling in single dendritic spines and thus reveal the signalingmechanisms that link synaptic activity and the induction of synaptic plasticity. This is mostly in the study of Ca2þ-dependent forms of synaptic plas-ticity for which many of the steps between Ca2þ influx and changes to the synapse are now known. This article introduces the new techniques used to investigate signaling in single dendritic spines and the neurobiological insights that they have produced. Each neuron typically receives 1000–10,000synaptic inputs and sends information to an axon, which branches to produce a similar number of synaptic outputs. Most excitatory postsynaptic terminals are associated with den-dritic spines, small protrusions emanating from the dendritic surface (Nimchinsky et al. 2002