What is the appropriate description level for synaptic plasticity?

Abstract

The hypothesis that learning memory and some aspects of development are mechanistically implemented by synaptic plasticity has gained significant experimental support (1, 2). At the cellular and molecular level synaptic plasticity is a very complex phenomenon, involving hundreds of molecular species, depending on the structure of dendrites and on ion channel concentrations. If we are to understand how high-level processes arise from synaptic plasticity, and not simply that they arise from synaptic plasticity, we must know how to best characterize plasticity theoretically. Such a characterization should account for key experimental results, yet at the same time it should be as simple as possible so that we can use it to explain how plasticity can lead to learning and memory. The article by Gjorgjieva et al. (3) in PNAS argues that a sufficient model of synaptic plasticity can depend only on spike pairs and triplets and that more-complex biophysical and molecular processes might not be needed. It also shows a correspondence between this triplet-based rule and the well-known phenomenological Bienenstock Copper Munro (BCM) learning rule (4).