Research Article
Associative Memory Cells in Engram Circuits
Jin-Hui WangThe joint acquisition and integrated storage of multiple exogenous signals are called as associative learning and memory. Endogenous signals that are generated during cognition and emotion based on exogenous signals can be memorized. The integrative storage of these exogenous and endogenous signals is essential for various events in life. In terms of basic units of engrams, associative memory cells are recruited in the brain in learning and cognition. The recruitment and refinement of associative memory cells work for memory retrievals, memory-relevant events and the reorganized learning of unitary signals that have been acquired. Associative memory cells are recruited by generating mutual synapse innervations among coactivated neurons within a single-modality brain area and across multi-modality brain areas. Associative memory cells in engrams are those cells that are able to encode the storage of associatively learned signals and receive synapse innervations carrying these signals. Associative memory cells are generally classified into primary associative memory cells in sensory cortices and secondary associative memory cells in brain areas relevant to cognition and emotion. The axons of primary associative memory cells innervate secondary associative memory cells. Mutual synapse innervations constitute the integrative storage and reciprocal retrieval of associated signals. Convergent synapse innervations to downstream neurons endorse the integrative cognition and emotion, such as associative thinking and logical reasoning. Divergent synapse innervations confer multiple uses of memorized signals. The interconnection between primary and secondary associative memory cells makes sensory sources be included in memory-relevant events. This review presents a comprehensive diagram about the recruitment and refinement of associative memory cells as well as their impacts in physiology, psychology and pathology for the society of memoriology.