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Presents information on a case study of a patient with a modality-specific problem in visual object recognition which can be linked to impaired stored descriptions for objects. Details on the case report; Examination of perceptual processing; Experimental results and discussion.

Discusses the case of a patient who presented a pattern of performance corresponding to optic aphasia (OA). Medical history of the patient; Results of neuropsychological testing; Types of error made by the patient during visual and tactile modality testins; Explanation of OA as a disconnection between visual and verbal semantic systems.

Deficits in the mental rotation of body parts and of external objects can be doubly dissociated (Rumiati, Tomasino, Vorano, Umiltà, & De Luce, 2001; Sirigu & Duhamel, 2001; Tomasino, Rumiati, & Umità, in press). The aim of this study was to replicate this finding and to then investigate the relevance of the specific hemispheres in these deficits. Nine patients with unilateral lesions (five in the Left Hemisphere and four in the Right) and 20 control subjects, performed a single task requiring mental rotation of hands, and two tasks requiring mental rotation of external objects. RH patients were impaired in the rotation of external objects, but showed intact performance on the rotation of hands; the opposite pattern was found for LH patients. These results support the view that the LH contributes to the mental rotation of hands, recruiting processes specific to motor preparation, while the RH is specialized for mental rotation of external objects. [ABSTRACT FROM AUTHOR]