A process analysis of the CA3 subregion of the hippocampus

Raymond P Kesner

doi:10.3389/fncel.2013.00078

Abstract

From a behavioral perspective, the CA3a,b subregion of the hippocampus plays an important role in the encoding of new spatial information within short-term memory with a duration of seconds and minutes. This can easily be observed in tasks that require rapid encoding, novelty detection, one-trial short-term or working memory, and one-trial cued recall primarily for spatial information. These are tasks that have been assumed to reflect the operations of episodic memory and require interactions between CA3a,b and the dentate gyrus (DG) via mossy fiber inputs into the CA3a,b. The CA3a,b is also important for encoding of spatial information requiring the acquisition of arbitrary and relational associations. All these tasks are assumed to operate within an autoassociative network function of the CA3 region. The CA3a,b also supports retrieval of short-term memory information based on a spatial pattern completion process. Based on afferent inputs into CA3a,b from the DG via mossy fibers and afferents from the entorhinal cortex into CA3a,b as well as reciprocal connections with the septum, CA3a,b can bias the process of encoding utilizing the operation of spatial pattern separation and the process of retrieval utilizing the operation of pattern completion. The CA3a,b also supports sequential processing of information in cooperation with CA1 based on the Schaffer collateral output from CA3a,b to CA1. The CA3c function is in part based on modulation of the DG in supporting pattern separation processes.

Highlights

This review article emphasizes the importance of behavioral functions of the CA3 subregion of the hippocampus
CA3c function is in part based on modulation of the dentate gyrus (DG) in supporting pattern separation processes
These are tasks that have been assumed to reflect the operations of episodic memory and require interactions between CA3a,b and the DG via mossy fiber inputs into the CA3a,b

Summary

INTRODUCTION

This review article emphasizes the importance of behavioral functions of the CA3 subregion of the hippocampus. After an anatomical description of the CA3a,b,c network, the influence of an autoassociative network function of the CA3 region in supporting mnemonic functions is presented. It should be noted that CA3a,b can be involved in short-term memory retrieval as evidenced by support for a pattern completion process. CA3 receives converging inputs from multiple input pathways; for example, perforant path inputs from the medial and lateral entorhinal cortex, mossy fiber inputs from the DG, and its own outputs fed back as inputs via the recurrent collaterals (Amaral and Witter, 1995). The medial septum and vertical limb of the diagonal band of Broca, in turn, provides cholinergic and GABAergic inputs into the hippocampus (Amaral and Witter, 1995). It should be noted that the CA3c regions do not have

Pattern completion and retrieval

Findings

CONCLUSION