Memory Storage in Distributed Cell Assemblies
Stefan Leutgeb, University of California, San Diego

Life-long memories are thought to be stored in networks of neurons that have stable connections (i.e., synapses) with each other. New memories are integrated into existing neural circuits by reorganizing the connectivity within a neuronal network. Hebb formulated a theory on the growth of cell assemblies (1), which predicted how neuronal activity in a subgroup of cells in a neural network could result in persistent synaptic changes within the same group of cells. Such synaptic reorganization is initiated by coincident neuronal activity (2) and is then maintained by growth processes that further stabilize and reorganize neuronal circuits (3). In addition, our understanding of memory formation on the systems level became importantly influenced by the finding that the medial temporal lobes have only a time-limited role in human declarative memory (4, 5). While mechanistic understanding of biochemical changes at synapses has increased, the neuronal circuit regulation for implementing these processes within and across brain structures are much less understood. Our symposium discusses recent advances in understanding how neuronal activity and experience-dependent modification of synapses may support the storage of memories within a brain region or across brain regions.

1. D. Hebb, The organization of behavior. (Wiley, New York, 1949).

2. T. V. Bliss, T. Lomo, J Physiol 232, 331 (Jul, 1973).

3. T. V. Bliss, G. L. Collingridge, Nature 361, 31 (Jan 7, 1993).

4. W. B. Scoville, B. Milner, J Neurol Neurosurg Psychiatry 20, 11 (Feb, 1957).

5. L. R. Squire, Neuron 61, 6 (Jan 15, 2009).

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