Authors:

LEE, A.C.H., Buckley, M.J., Gaffan, D., Epstein, R., HODGES, J.R. & GRAHAM, K.S.

Reference:

Year of publication:

2003

CBU number:

5824

Abstract:

Lesion studies in non-human primates suggest that the perirhinal cortex is involved in the processing of conjunctions of visual features. To date, however, neuropsychological studies have failed to support this view in humans. To investigate this discrepancy in the literature, non-mnemonic oddity tasks, in which subjects were required to select the odd stimulus from a visual array, were given to patients with damage to medial temporal lobe regions, including perirhinal cortex. A number of these tasks could be solved on the basis of single features (e.g., size, shape and colour), while the other tasks (e.g., oddity judgement for novel faces and objects) placed a significant demand on discriminating object features. Monkeys typically show deficits on the object but not the single feature tasks after ablations to perirhinal cortex (Buckley et al, 2001). Patients with predominant involvement of the hippocampus bilaterally (e.g., patients with Alzheimerís disease and cases with static pathology after anoxic episodes or encephalitis) performed within the normal range on both the single and object feature oddity tasks. By contrast, patients with semantic dementia and static cases with lesions to the medial temporal lobe, in whom there was documented perirhinal cortex damage, were unimpaired on the single feature oddity tasks, but performed significantly poorer on the perirhinal-dependent tests. These studies suggest that human perirhinal cortex may play a role in both perception and memory.