Two circuits to convert short-term memory into long-term memory.

Abstract

According to a brain model, encoding synapses record presynaptic axonal 'on-off' patterns as memory, and modulating synapses convert short-term memory into long-term memory by helping encoding synapses develop long-term potentiation and depression. Sensory organs conduct sounds and images as series of axonal 'on-off' patterns to encoding synapses of perceptive cortices where the patterns are recorded, computed, and rerouted to mesotemporal lobes, hippocampal formations and higher cortical centers. Mesotemporal lobes and hippocampal formations compute and convey the 'on-off' patterns to dorsomedial thalamic nuclei (circuit A), septal nuclei and mammillary bodies (circuit B), where the patterns are computed and conveyed to prefrontal lobes (circuit A) and anterior thalamic nuclei (circuit B) respectively. Anterior thalamic nuclei project axonal 'on-off' patterns to cingulate gyri that compute and convey the patterns to prefrontal lobes. Finally, prefrontal lobes send modulating axons to encoding synapses of perceptive cortices. Amnesia of Korsakoff's syndrome results from unilateral dysfunction of circuit A and contralateral dysfunction of circuit B, or bilateral dysfunction of either. The fact that there is more severe memory deficit in Alzheimer's disease than in Korsakoff's syndrome suggests that the former has a wider spread of failing synapses besides circuit A and circuit B.