Evaluating Evidence From Animal Models of Episodic Memory

A fundamental question in comparative cognition concerns the ability to remember back in time to an earlier event or episode. This ability is referred to as episodic memory. Whether nonhumans can be used to model human episodic memory has engendered much interest and debate for over 2 decades. The central hypothesis of an animal model of episodic memory is that, at the moment of the memory assessment, the animal remembers back in time to a specific earlier event or episode. I describe (a) an approach for evaluating evidence of episodic memory in animal models (b) what aspects of episodic memory are being modeled in animals (c) what standards ought to be applied to a candidate model of episodic memory in nonhumans (d) the first evidence of episodic memory in nonhumans, and (e) a brief overview of the diversity of approaches that are now available. The remainder of the article focuses on the development of a robust model of episodic memory in rats. Converging lines of evidence suggest that rats provide a good model for exploring episodic memory. This evidence includes studies that focus on (a) what-where-when memory (b) source memory (c) binding of episodic memories (d) memory of multiple Items in context using episodic memory (e) replay of episodic memories (f), recollection, and (g) answering an unexpected question after incidental encoding. In each of these domains, I describe evidence for episodic memory in the absence of nonepisodic judgments of familiarity. I end with some consideration of future directions.