Internal and external codes for location

Abstract

When navigating through the world, we can predict our next location on the basis of an internal sense of our location and velocity, but we can also orient to external visual sensory cues to update and stabilize this sense of location and velocity. A new experiment that mismatches the speed of visual cues and physical movement in rats shows that hippocampal network dynamics rapidly alternate between these functions within cycles of the 8-Hz theta oscillation. In one portion of the theta cycle, the internal sense of location drives the phase of firing independent of visual cues or self-motion cues, whereas in the other portion, the phases depend on a match of visual and self-motion inputs, manifesting as a reduction in place cell activity when there is a mismatch.