THE ROLE OF VISUAL-DISCRIMINATION DISORDERS AND NEGLECT IN PERCEPTUALCATEGORIZATION DEFICITS IN RIGHT AND LEFT-HEMISPHERE DAMAGED PATIENTS

This study was designed to investigate the role of visual sensory defi cits and neglect in perceptual categorization deficits in a group of 3 5 patients with unilateral cerebral lesions. From theoretical point of view, it was expected that right hemisphere lesions would play a crit ical role in eliciting perceptual categorization deficits which could not be accounted for by visual sensory deficits or neglect. The result s revealed that perceptual categorization deficits were not confined t o RHD patients, but they were also found in LHD patients. RHD patients were impaired regardless of the nature of the task (verbal vs. nonver bal), while LHD patients were impaired on nonverbal tasks, and in a le sser degree on verbal tasks. In both brain-damaged groups, perceptual categorization deficits were highly associated with visual sensory def icits, however, perceptual categorization deficits were also found wit hout impairments in the visual sensory system. Neglect seems to be a l ess important determinant of perceptual categorization deficits. The p resent findings are discussed in the light of Warrington's model of ob ject agnosia.