Somesthetic-visual matching disorders in right and left hemisphere-damaged patients.

Forty-nine patients with recent right (RHD) and left (LHD) hemispheric vascular lesions were compared on a task of somesthetic-visual matching of meaningful objects and of meaningless shapes. A selective impairment for shapes was found in RHD subjects, while LHD patients were impaired in object matching. This double dissociation conforms to the classical distinction between apperceptive and associative agnosia, and extends to the somesthetic modality the "double dissociation" between left and right hemispheric lesions and associative and apperceptive recognition disorders, which has been found in other modalities of agnosia.