• BMB Reports
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• v.51 no.8
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• pp.369-370
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• 2018

In previous studies, memory storage was localized to engram cells distributed across the brain. While these studies have provided an individual cellular profile of engram cells, their synaptic connectivity, or whether they follow Hebbian mechanisms, remains uncertain. Therefore, our recent study investigated whether synapses between engram cells exhibit selectively enhanced structural and functional properties following memory formation. This was accomplished using a newly developed technique called "dual-eGRASP". We found that the number and size of spines on CA1 engram cells that receive inputs from CA3 engram cells were larger than at other synapses. We further observed that this enhanced connectivity correlated with induced memory strength. CA3 engram synapses exhibited increased release probability, while CA1 engram synapses produced enhanced postsynaptic responses. CA3 engram to CA1 engram projections showed strong occlusion of long-term potentiation. We demonstrated that the synaptic connectivity of CA3 to CA1 engram cells was strengthened following memory formation. Our results suggest that Hebbian plasticity occurs during memory formation among engram cells at the synapse level.

• Korean Journal of Cognitive Science
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• v.7 no.3
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• pp.37-60
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• 1996

From the biopsychological point of view,learning could be defined as the processes to transfer the information that we obtain from environment to the neural circuits in the brain.In the studies to determine the biological substrates of learning and memory,there was a remarkable effort to identify neural circuits related with a specific type of learning and to describe the mechanixm of neural plasticity of learning and memory,under the assumption that the memory orinformation may be stored as a modificationof neural synapes in the central nerviys system.On the other hand,there was a different kind of tendency to analyze the mechanism of interactions between neural substrates involved in learning and memory,under the assumption that a specific information may be represented in the patterns of comples neural network of the central nervous system.The present review,in the former position.focused on the research methods and the chracteristics and finding of the investigations employing animal model systems to indentify the essential site of engram for learning and memory.Specifically,the review presents major advances in ourunderstanding of the memory trace circuit for a specific type of learning,with the use of animal model system,the detemination of the critical lodi of neuaral plastic chabges In learing abd memory,and the neurophysiological an biocemical mechanixms of the neural modifia by learint.