THE DIFFERENCES IN LEARNING-ABILITIES BETWEEN SPONTANEOUSLY HYPERTENSIVE (SHR) AND WISTAR NORMOTENSIVE RATS ARE CUE DEPENDENT

We examined the performance of spontaneously hypertensive (SHR) and Wi star normotensive (NT) rats in acquisition, retention after a 2-month interval, and reversal learning in two tasks: simultaneous brightness discrimination (Experiment I) and conditional discrimination of direct ional locomotor responses (Experiment II). In both tasks food reinforc ement was used. In Experiment I both SHR and NT groups comprised young er (3-month-old) and older (10-month-old) rats. In each experimental s tage SHRs of both age groups mastered the task earlier and made fewer errors than the respective NT groups. Reversal learning took longer th an acquisition of discrimination in both age groups of NT rats. Conver sely, reversal learning was an easier task for SHR. In Experiment II o nly younger rats were used. The forced turn at the start in the modifi ed T-maze was utilized as the cue to guide performance at the choice p oint of the maze. In acquisition and retention, rats were trained to s elect at the choice point the arm in the same direction as in the forc ed turn; in the reversal, opposite contingencies were applied. At all stages the choice accuracy of SHR was the same as that in NT rats. The contrasting findings of Experiment I and Experiment II indicate that SHR learned better than NT when exteroceptive visual stimuli were used , but performed at the same level as NT rats in the task where interoc eptive kinesthetic cues were relevant. We suggest that SHR pay more at tention to visual stimuli than NT rats. (C) 1995 Academic Press, Inc.