Authors:

BARENSE, M.D., Gaffan, D. & GRAHAM, K.S.

Reference:

Year of publication:

2006

CBU number:

6521

Abstract:

There has been considerable debate as to whether structures in the medial temporal lobe (MTL) support both memory and perception. Specifically, the perirhinal cortex may be involved in the perceptual discrimination of complex objects with a large number of overlapping features. To test this view, we administered a series of “oddity” tasks, in which subjects selected the odd stimulus from a visual array, to amnesic patients with either selective bilateral damage to the hippocampus or more extensive damage to MTL regions, including the perirhinal cortex. Whereas patients with damage limited to the hippocampus performed similarly to controls on all conditions, patients with perirhinal damage were significantly impaired when the task required a perceptual discrimination between objects with a large number of features in common. By contrast, if the same stimuli could be discriminated using simple visual features, these patients performed normally. These results suggest that rostral inferotemporal cortical regions, including perirhinal cortex, represent complex conjunctions of stimulus features necessary for perception of complex objects, whereas more caudal regions (e.g., V4, TEO) contain the components from which these conjunctions are formed. These findings indicate that memory and perception of complex objects is dependent upon the peririhinal cortex, but not the hippocampus, and challenge the view that the MTL is uniquely specialized for long-term declarative memory.