Associative memory in a pair of cortical cell groups with reciprocal projections

Abstract

We examine the functional hypothesis of bidirectional associative memory in a pair of reciprocally projecting cortical cell groups. Our simulation model features two-compartment neurons and synaptic weights formed by Hebbian learning of pattern pairs. After stimulation of a learned memory in one group we recorded the network activation. At high synaptic memory load (0.14 bit/ synapse) we varied the number of cells receiving stimulation input (input activity). The network “recalled” patterns by synchronized regular gamma spiking. Stimulated cells also expressed bursts that fascilitated the recall with low input activity. Performance was evaluated for one-step retrieval based on monosynaptic transmission expressed after ca. 35 ms , and for bidirectional retrieval involving iterative activity propagation. One-step retrieval performed comparably to the technical Willshaw model with small input activity, but worse in other cases. In 80% of the trials with low one-step performance iterative retrieval improved the result. It achieved higher overall performance after recall times of 60– 260 ms .