Role of the hippocampus in mediating interference as measured by pattern separation processes.

In order to understand the neural mechanism associated with specific forms of interference, this manuscript concentrates on the role of the dorsal and ventral dentate gyrus subregions of the hippocampus in rats. The computational modelers have suggested that the dentate gyrus can provide a neural mechanism that can operate to reduce interference between highly processed similar spatial, contextual or odor inputs to generate pattern separation functions. Pattern separation which is defined as a process to remove redundancy from similar inputs so that events can be separated from each other and interference can be reduced, and in addition can produce a more orthogonal, sparse, and categorized set of outputs. It appears that the anatomical organization of the hippocampus may provide the answer for the importance of interference in mnemonic processing of information. Therefore, in the first part of this paper an anatomical description of the inputs and outputs of the hippocampus as well as its intrinsic circuit is provided. This is followed by the presentation of data to support the role of the dorsal DG in supporting spatial pattern separation, dorsal CA1 in supporting temporal pattern separation for spatial locations and visual objects, ventral DG in supporting odor pattern separation, and ventral CA1 in supporting temporal pattern separation for odors.