Authors:

LEE, A.C.H., Bussey, T.J., Murray, E.A., HODGES, J.R. & GRAHAM, K.S.

Reference:

Year of publication:

2004

CBU number:

5825

Abstract:

Animal studies suggest that the perirhinal cortex processes conjunctions of object features while the hippocampus plays a particular role in spatial processing. To date, however, neuropsychological studies have failed to support this view in humans. To investigate this discrepancy in the literature, a visual concurrent discrimination task was given to two patient groups who had suffered damage to the medial temporal lobe, the majority following anoxic episodes or encephalitis. One patient group had selective damage to the hippocampus bilaterally while a second group had more extensive lesions of the medial temporal lobe, including the perirhinal cortex but not necessarily with lateral temporal lobe damage. The subjects were required to differentiate between two images from assorted stimulus categories (e.g. faces, objects, spatial scenes, abstract art and colour). The difficulty of the discrimination was manipulated by morphing between the two stimuli, thereby increasing feature overlap. The patients with predominant hippocampal damage performed normally except when asked to discriminate spatial scenes. By contrast, the patients with more extensive lesions to the medial temporal lobe were significantly poorer than controls in the discrimination of faces, objects and spatial scenes, but performed normally when asked to discriminate abstract art and colour. These findings are consistent with proposals that the human medial temporal lobe is not just involved in mnemonic processing.