Molecular approaches to learning and memory

We are now at the stage of neurophysiology where learning and memory can be subjects of studies at a strictly molecular level, on the basis of the well-established finding that these higher nervous activities are sustained by, and formed in, the physicochemical events of specified neural mechanisms in the brain. As for the neurophysiological process of memory, much evidence has shown that short-term memory and long-term memory probably result from different molecular events in the brain, i.e., the former from reversible chemical modification of the synapses concerned, and the latter from reorganization of the synapses following synthesis of protein and its axonal transport, which causes the enduring consolidation of memories. How does the experience of individual organisms trigger the protein synthesis in the brain required for long-term memory? What is the role of protein molecules thus formed? What is the mechanism for the regulation of gene expression in the reorganization of neuronal circuits? Many such difficult problems need to be solved. Recently, cholinergic and glutamatergic neuron networks have attracted much attention because there is a strong possibility that they play a critical role in memory. The clinical implication of these findings in human memory deficit, as exemplified in senile dementia, further emphasizes the importance of neurobiological elucidation of the molecular mechanism for learning and memory.