Declarative Association Memory

Abstract

Memory enables us to change our behavioral patterns based on past experiences. There are multiple memory systems in the human brain. One of those, declarative memory, is our “everyday-language memory” and enables us to describe the things that we remember. Other collections of memory are referred to as non-declarative memory. Both of these memory systems involve a form of association memory that connects one thing to another. However, while declarative association brings us sensory or declarative information when we recollect, non-declarative association couples a cue stimulus directly to a behavioral or autonomic response. On this account, declarative associations offer more flexibility than non-declarative because we are able to choose future actions based on the retrieved information. Declarative associations can be divided into two subcategories: episodic and semantic. Episodic associations accompany a particular spatiotemporal context in which a subject experienced an event, while semantic associations represent facts or knowledge extracted from individual experiences. Both are supported by the medial temporal lobe areas. In episodic associations, the hippocampus receives converging inputs from various association cortices via other medial temporal lobe areas, where several association processes occur before the signal reaches the hippocampus. The hippocampus does the final part of constructing associations among contents whose details are represented in other areas. Through repetition, the representations of content are directly linked as semantic associations in the temporal lobe, particularly in the perirhinal cortex. Perirhinal neurons represent between-domain associations as well as within-domain associations and spread the memory-retrieval signal back to the neocortex, where neuronal representations are coupled to mental imagery. The memory retrieval signal in the perirhinal cortex is also transmitted forward to the hippocampus in which the memory signal is combined with the other memory signals to reconstruct past events or future plans (“mental time travel”). The flexibility of declarative memory depends on its constructive process as well as its declarative components to be retrieved.