Working memory in aged rats.

The performances of young and aged rats were compared on a spatial (spatial delayed nonmatching-to-sample) and a nonspatial (object delayed nonmatching-to-sample) test of working memory. Although evidence was found that aging showed acquisition of both of these tasks, performance over different retention intervals of up to 60 s was normal once the task was mastered. An impairment was found, however, in the performance of the spatial test when the number of locations to be remembered on each trial was increased from one to two.

Effects of amygdaloid and amygdaloid-hippocampal lesions on object recognition and spatial working memory in rats.

Neurotoxic lesions of the amygdala did not affect the postoperative acquisition of a nonspatial test of object recognition (delayed nonmatching to sample) even when retention delays were increased from 0 s to 20 or 60 s, or when test stimuli were deliberately repeated within a session. Although these amygdaloid lesions did not alter forced-choice spatial alternation, they slightly increased neophobic responses to novel foods and environments. In contrast, combined amygdalohippocampal (A + H) lesions impaired performance on the object recognition task when the retention intervals were increased beyond 0 s and when test stimuli were repeated within a session.