Hippocampal spatial view cells, place cells, and concept cells: View representations

Apr 10, 2023Hippocampus

Brain cells for viewing space, specific places, and concepts: How they represent what we see

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Abstract

Evidence suggests that spatial view cells in primates, including humans, are crucial for episodic memory and navigation.

Allocentric representations from spatial view cells help determine the location of objects and rewards in the environment.
Memory and navigation typically rely on visual cues that define locations, rather than on unmarked places without local identifiers.
Mixed representations can develop when training involves limited combinations of spatial views and places.
Rodents may use widely spaced environmental cues along with local olfactory and tactile information to navigate due to their lower visual acuity.
View-point dependent allocentric representations could transition to a view-point independent format for better memory and navigation.

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A commentary is provided on issues raised in the Special Issue of Hippocampus (2023) on hippocampal system view representations. First, the evidence for hippocampal and parahippocampal spatial view cells in primates including humans shows that the allocentric representations provided by at least some of these cells are very useful for human memory in that where objects and rewards are seen in the world "out there" is a key component of episodic memory and navigation. Spatial view cell representations provide for memory and navigation to be independent of the place where the individual is currently located and of the egocentric coordinates of the viewed location and the facing direction of the individual. Second, memory and navigation in humans are normally related to the visual cues encoded by spatial view cells that define a location "out there" such as a building, hill, and so forth, not to an unmarked place without local cues and identified only by distant environmental/room cues. Third, "mixed" representations, for example of particular combinations of spatial view and place, can arise if the training has been for only some combinations of place and view, for that is what can then be learned by the hippocampus. Fourth, rodents, with their much less good visual acuity (~1 cycle/° in rats, compared with ~60 cycles/° for the human fovea), and rodents' very wide viewing angle for the world (~270°) might be expected, when using the same computational mechanisms as in primates, to use widely spaced environmental cues to define a place where the rodent is located, supported by inputs about place using local olfactory and tactile cues. Fifth, it is shown how view-point dependent allocentric representations could form a view-point independent allocentric representation for memory and navigation. Sixth, concept cells in humans and primates with connectivity to the hippocampus are compared.

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