Spatial representations of self and other in the hippocampus

The representation of others in space Different sets of neurons encode the spatial position and orientation of an organism. However, social animals need to know the position of other individuals for social interactions, observational learning, and group navigation. Surprisingly, very little is known about how the position of other animals is represented in the brain. Danjo et al. and Omer et al. now report the discovery of a subgroup of neurons in hippocampal area CA1 that encodes the presence of conspecifics in rat and bat brains, respectively. Science, this issue p. 213, p. 218 A group of neurons in hippocampal area CA1 of rats represents the position of conspecifics. An animal’s awareness of its location in space depends on the activity of place cells in the hippocampus. How the brain encodes the spatial position of others has not yet been identified. We investigated neuronal representations of other animals’ locations in the dorsal CA1 region of the hippocampus with an observational T-maze task in which one rat was required to observe another rat’s trajectory to successfully retrieve a reward. Information reflecting the spatial location of both the self and the other was jointly and discretely encoded by CA1 pyramidal cells in the observer rat. A subset of CA1 pyramidal cells exhibited spatial receptive fields that were identical for the self and the other. These findings demonstrate that hippocampal spatial representations include dimensions for both self and nonself.