A nonlinear model of memory

Summary form only given. The model described attempts to bridge the gap between neuron and cognitive function. It is based on the well-known ´searchlight´ model of memory, in which memory retrieval is likened to the beam of a searchlight sweeping through the cortex until it lights up a certain place which has been appropriately silvered. Storage occurs as the silvering process when the searchlight beam is focussed strongly enough on a piece of virgin cortex: this process is to be implemented neurophysiologically in terms of the searchlight being the thalamus (and its reticular nucleus), which has strong and reciprocal connections with nearly all regions of the neocortex. The steering of the searchlight is proposed to be formed by the HCF, using the plastic property of long-term enhancement. It is through the internal mechanisms of the HCF return-loop (and also the HCF-thalamus-cortex-HCF loop) that memory is encoded as a fixed point in the space of cortical inputs to the HCF and hippocampal synaptic weights, and recalled by short-term plastic modification of the weighting part of the map. Persistence of earlier memories on hippocampectomy is explained in this model.<>