Associative Memory Cells in Memory Trace

Abstract

Associative memory is characterized as the integrative storages and the reciprocal retrievals of associated signals after their joint acquisitions. Basic units in memory traces should be morphological and functional identities to work for memory-relevant processes. Beyond the concepts of memory traces, engrams, cell assemblies, and neural plasticity, associative memory cells have been functionally and structurally identified, which encode the integrative storage and reciprocal retrieval of associated signals as well as receive synapse innervation from coactivated brain areas. Associative memory cells are identified as primary associative memory cells in sensory cortices to memorize exogenous signals and secondary associative memory cells in sensory downstream brain areas, such as the prefrontal cortex, amygdala, and hippocampus, to memorize endogenous signals generated from cognitive events and emotional reactions. Based on experimental data, these associative memory cells have the following characters. They receive synapse innervations from the coactivated brain areas in a reciprocal manner. They are able to encode the associated signals acquired in associative learning and generated in integrative cognitions. Their encoded signals and received synapse innervations come from cross-modal and intramodal sources. Their axons innervate their downstream brain regions in convergent and divergent manners. Associative memory cells and their mediated memory formation are influenced by the chain reaction including neuronal activation, epigenetic process, and the expressions of genes and proteins in relevance to axon prolongation and synapse formation. Working principles of associative memory cells are based on their reception of synapse innervations from multiple sources and mutual synaptic innervations by the coactivations, as well as neuronal encoding capability and synaptic transmission efficacy. Moreover, their functional states are modulated by the arousal system that release monoamine and acetylcholine as well as by hormones. These associative memory cells constitute the foundations of memory-related physiological and psychological processes as well as memory deficits in pathology.