CONSTRAINTS AND THE EMERGENCE OF FREE EXPLORATORY-BEHAVIOR IN RAT ONTOGENY

The present study attempts to combine the study of spatial learning wi th the study of open field behavior. We examine rat moment-to-moment b ehavior in the wide context of i) a large testing environment, ii) rep eated exposures, and iii) development. Previous studies have shown tha t in adult rats, exploratory behavior of a novel environment is organi zed around a reference place termed the rat's home base. In this study we show that the appearance of a homebase is a singular stage in onto geny, marking the transition from a low to a high scatter of movement in the environment. The increase in scatter is characterized by the ap pearance of several additional reference places. We suggest that the r at connects these reference places gradually and in a regular fashion. To do so we employ statistical filters which extract the principal pl aces visited by the rat, and use measures of diversity which estimate the scatter of movement around these places. The presented data are th e first derived from unconstrained behavior, supporting the hypothesis that the rat's cognitive space is represented in terms of local chart s eventually combined into a global map.