The Integration of Goal-Directed Signals onto Spatial Maps of Hippocampal Place Cells

Abstract

Summary: Spatial firing of hippocampal place cells varies depending on the animal’s behavior relative to its goals. Here, rats were trained to approach visually guided reward ports in a two-dimensional open field. Hippocampal place cells encoded two independent pieces of information, spatial representation and goal-directed representation, by amplifying firing rates within their place fields specifically while the animal was moving toward a specific goal location. Irrespective of running speed and direction, substantial place-selective firing was observed that sustained a basal spatial map independent of goal-directed signals. When animals were allowed to freely forage in the field, in-field firing rates similarly increased when the animals transiently ran toward remembered goal locations. Disruption of medial septal activity significantly decreased goal-directed firing while maintaining spatial representation patterns. The findings indicate that the integrated encoding of spatial and goal-directed signals by hippocampal circuits is crucial for flexible spatial navigation to a goal location. : Aoki et al. find that firing rates of CA1 neurons increase when rats are running toward a goal location irrespective of the positional relationship between their place fields and goal location. The results suggest possible neurophysiological mechanisms for encoding place-selective and goal-directed signals by a hippocampal cell. Keywords: place cells, hippocampus, goal-directed behavior, theta oscillation, medial septum