Signal flow in a prefrontal cortical circuit model for working memory loading

The active storage process for working memory, which is substantiated by a specific sustained activity of a population of neurons in the prefrontal co rtex, is a circuit property of the cortex. To analyze the circuit mechanism s of this process, we constructed a two-layer prefrontal cortical circuit m odel. The network with asymmetric inter-laminar connections produces transi ent, cue-period activity in one layer and delay-period activity in the othe r layer. The peak firing rate in the delay-period is low enough even though the model neurons do not have NMDA-type channels. The simulation shows tha t the postsynaptic currents have layer-specific spatio-temporal profiles, w hich are necessary for the coexistence of the different activity patterns. (C) 2001 Elsevier Science B.V. All rights reserved.