HIPPOCAMPAL AND AMYGDALOID INVOLVEMENT IN NONSPATIAL AND SPATIAL WORKING-MEMORY IN RATS - EFFECTS OF DELAY AND INTERFERENCE

Parametric manipulations of the task demand were used to examine the r ole of the hippocampus and amygdala in nonspatial and spatial working memory in rats. Hippocampal lesions produced an immediate and long-las ting impairment of nonspatial working memory in an operant task. The m emory deficits increased as the delay interval and the amount of proac tive interference increased. Hippocampal lesions severely impaired spa tial working memory in spatial alternation. Extensive postoperative te sting reduced the magnitude of impairment of nonspatial but not spatia l working memory. Amygdaloid lesions did not impair any aspect of perf ormance in 2 tasks. The results suggest that the hippocampus, but not the amygdala, is involved in working memory and the task demand is a c ritical determinant for observing impairments of nonspatial working me mory following hippocampal lesions.