Cellular and molecular approaches to memory storage.

There has been nearly a century of interest in the idea that information is stored in the brain as changes in the efficacy of synaptic connections on neurons that are activated during learning. The discovery and detailed report of the phenomenon generally known as long-term potentiation opened a new chapter in the study of synaptic plasticity in the vertebrate brain, and this form of synaptic plasticity has now become the dominant model in the search for the cellular bases of learning and memory. To date, considerable progress has been made in understanding the cellular and molecular mechanisms underlying synaptic plasticity and in identifying the neural systems which express it. In parallel, the hypothesis that the mechanisms underlying synaptic plasticity are activated during learning and serve learning and memory has gained much empirical support. Accumulating evidence suggests that the rapid activation of the genetic machinery is a key mechanism underlying the enduring modification of neural networks required for the laying down of memory. These advances are reviewed below.