The role of the hippocampus in recognition memory.

Amnesic patients with focal limbic lesions in the hippocampus demonstrate normal or near normal performance on the Warrington Recognition Memory Test (WRMT) suggesting that the hippocampi may not be critical structures in these tasks. To further investigate the role of the hippocampi in recognition memory we examined WRMT performance in 99 (44 right, 55 left) patients with unilateral temporal lobe pathology identified on MRI. The patients were divided into two groups. Group 1 (n = 90) were patients with hippocampal sclerosis (40 right, 50 left). Group 2 were patients with MRI evidence of hippocampal sclerosis and cortical dysgenesis, (4 right, 5 left). Analyses of variance revealed a significant interaction between laterality and pathology group for the recognition memory for words (RMW) task. The patients with left hippocampal sclerosis and cortical dysgenesis obtained significantly lower scores than the other patient groups. There was a significant effect of pathology group on the recognition memory for faces task (RMF). The patients with hippocampal sclerosis and cortical dysgenesis obtained lower scores than the patients with hippocampal sclerosis, regardless of the laterality of their pathology. Post-operative WRMT deficits in the right and left hippocampal sclerosis groups were material specific. The clinical utility of the WRMT in the pre-surgical investigation of temporal lobe epilepsy patients and the role of the hippocampus in recognition memory are discussed in the light of these findings.