  We present a simple biophysical model for the coupling between synaptic
transmission and the local calcium concentration on an enveloping astrocytic
domain. This interaction enables the astrocyte to modulate the information flow
from presynaptic to postsynaptic cells in a manner dependent on previous
activity at this and other nearby synapses. Our model suggests a novel,
testable hypothesis for the spike timing statistics measured for rapidly-firing
cells in culture experiments.
