Effects of peripheral and central visual impairment on mental imagery capacity.

This paper reviews a number of behavioral, neuropsychological and neuroimaging studies that bear on the question of whether and how visual disorders of peripheral or central origin lead to disorders of mental imagery capacity. The review of the literature suggests that in cases of blindness of peripheral origin lack of vision can progressively lead to representational disorders. However, in patients suffering from peripheral visual deficits, representational disorders can partially or completely be compensated by other sensory modalities as well as by cortical reorganization. Interestingly, in brain-damaged patients, neurovisual disorders following occipital or parietal lesions are not systematically associated with representational deficits, thus demonstrating that visual perception and visual imagery may not rely on the same cortical structures as previously hypothesized. Impairments seen on mental imagery tasks among brain-damaged patients with visual and/or spatial deficits might be due to an often co-existing attentional deficit. We discuss this possible dissociation between visual perception and visual mental imagery and its implications for theoretical models of mental representation.