CHARACTERIZING SYNAPTIC PLASTICITY WITH AN ACTIVITY DEPENDENT MODEL.
Recent studies of the interactions between pharmacologic agents and ion channels in excitable membrane have yielded an analytical characterization of use- or activity-dependent processes. Using this model and observations of habituation and sensitization in Aplysia, the authors derive a closed-form activity-dependent model of synaptic plasticity that exhibits the sigmoid form suggested by certain neural-net models. This characterization mimics some of the frequency-dependent features of habituation and sensitization. The model shows both the activity-dependent reduction in transmitter release found with habituation and the activity-dependent reduction in potassium conductance associated with sensitization. The results imply that complementary to frequency encoding of stimulus strengths, synaptic plasticity is encoded through pulsewidth modulation of the action potential.
