Conjunctive representations in learning and memory: Principles of cortical and hippocampal function.

Abstract

The authors present a theoretical framework for understanding the roles of the hippocampus and neocortex in learning and memory. This framework incorporates a theme found in many theories of hippocampal function: that the hippocampus is responsible for developing conjunctive representations binding together stimulus elements into a unitary representation that can later be recalled from partial input cues. This idea is contradicted by the fact that hippocampally lesioned rats can learn nonlinear discrimination problems that require conjunctive representations. The authors' framework accommodates this finding by establishing a principled division of labor, where the cortex is responsible for slow learning that integrates over multiple experiences to extract generalities whereas the hippocampus performs rapid learning of the arbitrary contents of individual experiences. This framework suggests that tasks involving rapid, incidental conjunctive learning are better tests of hippocampal function. The authors implement this framework in a computational neural network model and show that it can account for a wide range of data in animal learning.

The Temporal Context Model in Spatial Navigation and Relational Learning: Toward a Common Explanation of Medial Temporal Lobe Function Across Domains.

“…Transitive inferences were a consequence of an associative gradient across the stimuli to the "dig" response. The Complementary Learning Systems model (O'Reilly & Rudy, 2001) postulates that transitive performance is a consequence of overlapping hippocampal stimulus representations. In that model, however, correct responding depends on network dynamics to affect pattern completion.…”

Dissociations in Hippocampal and Frontal Contributions to Episodic Memory Performance.

“…Models of memory emphasize networks, with the medial temporal lobe working in concert with the cerebral cortex (Eichenbaum, Schoenbaum, Young, & Bunsey, 1996;O'Reilly & Rudy, 2001). Although our results examined the relationships between the hippocampus and memory accuracy on the one hand, and frontal structures and strategy use on the other, our findings are compatible with these models.…”

Temporally graded, context-specific retrograde amnesia and its alleviation by context preexposure: Effects of postconditioning exposures to morphine in the rat.

“…O'Reilly and Rudy (2001) have also described a model of stimulus representation that addresses the question of what rats might learn across preexposure to protect against the amnestic effects of postconditioning exposures to morphine. This model invokes complementary learningϪmemory systems in the hippocampus and cortex.…”