CORTICAL PLASTICITY - FROM SYNAPSES TO MAPS

It has been clear for almost two decades that cortical representations in adult animals are not fixed entities, but rather, are dynamic and are continuously modified by experience. The cortex can preferentially allocate area to represent the particular peripheral input sources th at are proportionally most used. Alterations in cortical representatio ns appear to underlie learning tasks dependent on the use of the behav iorally important peripheral inputs that they represent. The rules gov erning this cortical representational plasticity following manipulatio ns of inputs, including learning, are increasingly well understood. In parallel with developments in the field of cortical map plasticity, s tudies of synaptic plasticity have characterized specific elementary f orms of plasticity, including associative long-term potentiation and l ong-term depression of excitatory postsynaptic potentials. Investigato rs have made many important strides toward understanding the molecular underpinnings of these fundamental plasticity processes and toward de fining the learning rules that govern their induction. The fields of c ortical synaptic plasticity and cortical map plasticity have been impl icitly linked by the hypothesis that synaptic plasticity underlies cor tical map reorganization. Recent experimental and theoretical work has provided increasingly stronger support for this hypothesis. The goal of the current paper is to review the fields of both synaptic and cort ical map plasticity with an emphasis on the work that attempts to unit e both fields. A second objective is to highlight the gaps in our unde rstanding of synaptic and cellular mechanisms underlying cortical repr esentational plasticity.