Semantic memory refers to our general world knowledge that encompasses memory for concepts, facts, and the meanings of words and other symbolic units that constitute formal communication systems such as language or math. In the classic hierarchical view of memory, declarative memory was subdivided into two independent modules: episodic memory, which is our autobiographical store of individual events, and semantic memory, which is our general store of abstracted knowledge. However, more recent theoretical accounts have greatly reduced the independence of these two memory systems, and episodic memory is typically viewed as a gateway to semantic memory accessed through the process of abstraction. Modern accounts view semantic memory as deeply rooted in sensorimotor experience, abstracted across many episodic memories to highlight the stable characteristics and mute the idiosyncratic ones. A great deal of research in neuroscience has focused on both how the brain creates semantic memories and what brain regions share the responsibility for storage and retrieval of semantic knowledge. These include many classic experiments that studied the behavior of individuals with brain damage and various types of semantic disorders but also more modern studies that employ neuroimaging techniques to study how the brain creates and stores semantic memories. Classically, semantic memory had been treated as a miscellaneous area of study for anything in declarative memory that was not clearly within the realm of episodic memory, and formal models of meaning in memory did not advance at the pace of models of episodic memory. However, recent developments in neural networks and corpus-based tools for modeling text have greatly increased the sophistication of models of semantic memory. There now exist several good computational accounts to explain how humans transform first-order experience with the world into deep semantic representations and how these representations are retrieved and used in meaning-based behavioral tasks. The purpose of this article is to provide the reader with the more salient publications, reviews, and themes of major advances in the various subfields of semantic memory over the past forty-five years. For more in-depth coverage, we refer the reader to the manuscripts in the General Overviews section.
Neural activity reveals interactions between episodic and semantic memory systems during retrieval.
