Spatial representations in the primate hippocampus, and their functions in memory and navigation

Abstract

Hippocampal spatial view neurons in primates respond to the place where a monkey is looking, with some modulation by place. In contrast, hippocampal neurons in rodents respond mainly to the place where the animal is located. We relate this difference to the development of a fovea in primates, and the highly developed primate visual system which enables identification of what is at the fovea, and a system for moving the eyes to view different parts of the environment. We show that the spatial view representation in primates is allocentric, and provide new animations using recorded neuronal activity to illustrate this. We also show that this spatial representation becomes engaged in tasks in which the location ‘out there’ in a scene of objects and rewards must be remembered. We show that this representation of space being viewed provides a framework for the encoding of episodic memory and the recall of these memories in primates including humans, with hippocampal neurons responding for example in a one-trial object / place recall task. These functions of the primate hippocampus in scene-related memory, provide a way for the primate hippocampus to contribute to actions in space and navigation. We consider in a formal model the mechanisms by which these different spatial representations may be formed given the presence of the primate fovea, and how these mechanisms may contribute to the representations found during navigation in a virtual environment.