Associative visual agnosia resulting from a disconnection between intact visual memory and semantic systems

We report the case of a patient (RC) who developed a severe visual agnosia, associated to alexia without agraphia, color anemia and amnesia, following an ischemic stroke in the territory supplied by the left posterior cerebral artery. Based on his proficient performance on tests evaluating analysis of elementary visual features, formation of viewer-centered and object-centered representations of visual stimuli and discrimination between drawings representing real and unreal objects, we concluded that the critical locus of deficit was a disconnection between the normally functioning visual memory store and the semantic system. RC's disturbance in visual processing of human faces paralleled his recognition disorder of other classes of objects. The possible contribution of neurobiological factors in determining RC's agnosic deficit is discussed.