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

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.