A COMPARISON OF OLD AND YOUNG-RATS PERFORMANCE ON A TEST OF NONMATCHING-TO-SAMPLE - AN ANALYSIS OF AGE-RELATED ENCODING AND MEMORY DEFICITS

Using a multiple probe testing procedure (Roitblat, 1980), young and o ld rats were tested on a nonmatching-to-sample (NMTS) task in a three- arm maze. Subjects were forced to visit two different arms successivel y and, after variable delays, were required to choose the nonmatching arm, Incorrect responses on an initial probe run were followed by a se cond probe run. On no-delay trials, old rats performed poorly on first probe runs but they improved significantly on second probe runs. At l onger delays, old rats exhibited faster rates of decline than did youn g rats, The results indicated that old rats suffered a decline in thei r ability to encode new information and rapid memory loss, and that th e two deficits combined to adversely affect overall performance. Resul ts were related to neuropsychological evidence that implicated prefron tal and hippocampal dysfunction in the types of age-related deficits o bserved in the present study.