Long-term plasticity of hippocampal interneurons during in vivo memory processes.

Formation of a cell assembly, a group of cortical neurons that function co-operatively to sustain an active memory trace, arises from changes in the connections between neurons. Establishment of memory traces is thought to rely on long-term plasticity in excitatory glutamatergic synapses interconnecting principal cells. In addition, recent studies in the hippocampus in vivo indicate that reconfiguration of GABAergic inhibitory interneuron activity also occurs during long-term memory encoding. Recent experiments in anesthetized, as well as in freely moving animals, demonstrate that learning-related hippocampal activities are associated with persistent changes in GABAergic interneuron firing rates and alterations in protein expression levels regulating GABA release.