A PHASE PLANE REPRESENTATION OF RAT EXPLORATORY-BEHAVIOR

Rat spontaneous spatial behavior is considered to be stochastic and is therefore commonly analyzed in terms of cumulative measures. Here, we suggest a method which generates a moment-to-moment representation of this behavior. It has been proposed earlier that rat spatial behavior can be partitioned into natural units termed excursions (round trips) performed from a reference place termed the rat's home base. We offer a phase plane representation of excursions (plotting the rat's moment ary location against its momentary velocity). The results reveal a geo metrical pattern, typical of young age and early exposure. It consists of low velocity and intermittent progression while moving away from t he home base (upstream segment), and high velocity while moving back t o it (downstream segment). The asymmetry between the two segments defi nes a field of significance in the rat's operational world. This field undergoes regular transformations, revealing thereby the rat's strate gy of occupancy of the environment. The presented dynamics could provi de a framework for the interpretation of concurrent neural events asso ciated with navigation and spatial memory.