Fear Conditioning and Synaptic Plasticity

Since its initial characterization, synaptic plasticity has been a leading candidate cellular mechanism for the storage of information in the nervous system. However, to this date there has been no direct demonstration that synaptic plasticity occurs during acquisition of memory. In this article we review the mechanisms that underlie induction, expression, and maintenance of synaptic plasticity. We propose that all of these processes serve as a molecular fingerprint that can be used to probe whether synaptic plasticity has occurred in the brain. We then examine the molecular mechanisms engaged during formation of conditioned fear memory and compare them to the mechanisms engaged by synaptic plasticity. Finally, we review several studies that have attempted to measure synaptic plasticity . in vivo. Given the enormous amount of data indicating that synaptic plasticity occurs during formation of conditioned fear memory, we conclude that synaptic plasticity plays an important role in at least some aspects of memory formation.