SENSORY GATING IN A COMPUTER-MODEL OF THE CA3 NEURAL-NETWORK OF THE HIPPOCAMPUS

We have developed a unique computer model of the CA3 region of the hip pocampus that simulates the P50 auditory evoked potential response to repeated stimuli in order to study the neuronal circuits involved in a sensory processing deficit associated with schizophrenia. Our compute r model of the CA3 hippocampal network includes recurrent activation f rom within the CA3 region as well as input from the entorhinal cortex and the medial septal nucleus, We used the model to help us determine if the cortical and septal inputs to the CA3 hippocampus alone are res ponsible for the gating of auditory evoked activity, or if the strong recurrent activity within the CA3 region contributes to this phenomeno n. The model suggests that the medial septal input is critical for nor mal gating; however, to a large extent the activity of the medial sept al input can be replaced by simulated stimulation of the hippocampal n eurons by a nicotinic agonist. The model is thus consistent with exper imental data that shaw that nicotine restores gating of the N40 evoked potential in fimbria-fornix lesioned rats and of the P50 evoked poten tial in schizophrenic patients. (C) 1996 Society of Biological Psychia try