The effect of dynamic synapses on spatiotemporal receptive fields in visual cortex

Temporal dynamics are a general feature of synaptic transmission. Recently, novel aspects of temporal dynamics of synaptic transmission have been reported in the neocortex. Here, we examine the possible effects of these dynamics on the spatiotemporal receptive fields of simple cells in V1. We do this by examining a simple model of a cortical neuron that displays stimulus orientation selectivity as a consequence of the pattern of thalamocortical synaptic weights. In our model, the receptive field structure is encoded functionally in either presynaptic probability of release or postsynaptic efficacy. We show that these different assumptions about the origin of receptive field structure lead to very different spatiotemporal dynamics in the case of flashed-bar stimulus. In addition, the results of the reverse correlation study suggest a possible test for differentiating between models. We also show that the temporal code induced by dynamic synapses can be used to distinguish between different inputs that induce the same average firing rate.