We remember things from our own first-person perspective, the way we experienced them. The hippocampus is the region where these egocentric, episodic memories are made. Yet the hippocampus also encodes spatial information in a decidedly non-egocentric manner, using place cells and grid cells to form a generalized map of the external environment. How does one region of the brain manage both of these?

James Knierim’s lab at Hopkins has reconciled this seeming discrepancy in a manner Talmudic in its neatness: there’s no contradiction! Egocentric spatial information is encoded by one population of neurons in the hippocampus, and allocentric spatial information is encoded by a different population of cells in the hippocampus. Voila, problem solved.

Neuroscientists like Knierim use the word “allocentric” to denote a way of coding spatial information that defines the location of an object relative to other objects, as opposed to relative to the self. (Psychologists use it to describe someone whose interest, attention, and actions are focused on others rather than themselves.) Either way, its opposite is egocentric: spatial information (and/or one’s interest) with the self as the primary reference.