Reducing the temporal demands of the Morris place-learning task fails to ameliorate the place-learning impairment of preweanling rats

Abstract

Rats less than 20 days old display no evidence of place learning when trained in the Morris (1981) water task. In the present experiment, we evaluated the possibility that this impairment was a result of the immature “temporary memory buffer” that Rawlins (1985) has proposed as being critical for successful place learning. To evaluate this hypothesis, we reduced to a minimum the temporal demands of the Morris place navigation task by training pups of different ages to swim directly to a visible platform in a fixed location. All pups were then tested for place learning on the probe trial with no escape platform in the pool. In spite of being trained with a procedure that greatly reduced the temporal demands of the task, the 19-day-old pups displayed no learning of the platform’s location. Several measures of place learning indicated that 22-day-olds could learn the location of the platform. Our data thus provide no support for the hypothesis that young rats are impaired on place-learning task because of an immature temporary memory buffer. © 1988, Psychonomic Society, Inc.. All rights reserved.