Multiplexing of Self and Other Information in Hippocampal Ensembles

The hippocampus is essential for spatial navigation and memory and harbors place cells, coding an animal’s location in space. The hippocampus has also been suggested to code social information, such as about the spatial position of conspecifics. "Social place cells" have been reported for tasks where an observer mimics the behavior of a demonstrator. We examined whether hippocampal neurons may encode the behavior of a minirobot, however without requiring the animal to mimic it. Rather than finding social place cells, we observed that robot behavioral patterns modulate place fields coding animal position. During task performance, the rat’s own positions correlated with robot movements. We found that hippocampal ensembles coded information about robot movement patterns, even when correcting for rat position. Interneurons were more informative on robot movements than principal cells. In conclusion, when the animal’s own behavior is conditional on external agents, the hippocampus multiplexes information about self and others.