The role of the amygdala and the hippocampus in working memory for spatial and non-spatial information

Male rats received either electrolytic or sham lesions bilaterally into the amygdala, hippocampus or amygdala plus hippocampus, or were assigned to an unoperated control group. After the postoperative recovery period all lesioned and control animals were tested for the ability to master a spatial delayed non-matching-to-sample (DNMS), a visual DNMS and a visuo-tactile DNMS. Retention of these paradigms was evaluated 24 h after the last respective training session. Bilateral lesions of the amygdala severely disrupted the acquisition and retention of a DNMS paradigm with visual and visuo-tactile cues as discriminative stimuli and had no effect on the acquisition and retention of a spatial DNMS. On the contrary, bilateral lesions of the hippocampus impaired the acquisition and retention of spatial DNMS, but the animals with these lesions showed an acquisition and retention of the visual and visuo-tactile DNMS paradigms significantly better than those of animals with amygdala lesions. Combined lesions of the amygdala and hippocampus severely disrupted the acquisition and retention of the 3 paradigms. The contribution of the amygdala and the hippocampus in the working memory for spatial and non-spatial information is discussed.