Advantages of Hierarchical Generalization and Storage of Representations of “Object–Place” Associations in the Hippocampal Fields (a hypothesis)

Abstract

Existing data from experimental studies of the features of the processing of sensory information in the hippocampus and neocortex are reviewed, along with results obtained by modeling the perception of information in the neocortex. Moving upward through the trisynaptic hippocampal pathway, the “place” fields of neurons expand and the overlap between their receptive fields increases. These effects point to generalization of the information processed. The results of this analysis suggest the hypothesis that movement through all the hippocampal fields is associated with hierarchical generalization of information relating to “object–place” associations. The complexity of the neuronal representations of “object–place” associations formed and permanently stored in the hippocampal fields increases as signals move from the entorhinal cortex to the hierarchically higher dentate gyrus, field CA3, and field CA1. Thus, extraction of information relating to “object–place” associations with certain details from memory requires access to the hippocampal field in which the associations were processed and remembered with the required level of detail. By analogy with the neocortex, it is suggested that this information processing in the hippocampus avoids the combinatorial explosion and supports the storage (remembering) of associations accumulated through life. The mechanism proposed here may supplement the existing multiple trace theory, which proposes that the hippocampus is an integrating component of the memory trace and is always involved in recall of past episodes.