SHORT-STOPS IN RATS WITH FIMBRIA-FORNIX LESIONS - EVIDENCE FOR CHANGEIN THE MOBILITY GRADIENT

Rats with damage to the hippocampal formation and allied structures ar e hyperactive in many test situations but the cause of this hyperactiv ity is not known. Here the activity of control rats and rats with fimb ria-fornix lesions is documented in tests of overnight activity. Detai ls of activity are then characterized from video recordings of behavio r in an open field. Rats with fimbria-fornix lesions make significantl y more stops of shorter duration and thus more individual trips than c ontrol rats but they do not differ in the distance traveled on individ ual trips or in travel speed. It is suggested that the main difference between fimbria-fornix rats and control rats is that when fimbria-for nix rats stop they remain ''still'' for shorter durations than do cont rol rats. This finding is discussed in relation to a theory of locomot or/exploratory behavior, and in relation to its implications with resp ect to the performance of fimbria-fornix rats in studies of learning a nd memory. (C) 1994 Wiley-Liss, Inc.