Using the Change Manager Model for the Hippocampal System to Predict Connectivity and Neurophysiological Parameters in the Perirhinal Cortex

Figure 5

Competition circuitry within the hippocampus proper to select cortical columns for receptive field expansions. Mossy cells in the dentate gyrus target CA3 pyramidal neurons with similar receptive fields, directly which is excitatory and in an inhibitive manner via interneurons. As the activity of the mossy cell increases, inhibition becomes predominant. If the situation being processed by the cortex is familiar, there will be strong input from the entorhinal cortex corresponding with all relevant cortical areas. This will mean strong activity of all relevant granule cells, and the predominant effect of these cells on all the CA3 pyramidal neurons will be inhibitive. If there is novelty in some aspects of the current situation, some granule cells will be less active, allowing CA3 activity to develop. Activity of CA3 neurons corresponding with the cortical areas needing receptive field expansions will develop, and as it develops it will be self-limited because it drives increased activity in the dentate gyrus. So the CA3 activity will be proportional to the degree of novelty in the current experience and will be targeted on the cortical columns most appropriate for the necessary expansions to respond to the novelty. Once the competition process is complete, CA3 drives CA1 activity, which sends signals back to the cortex to drive expansions.