Blindsight and insight in visuo-spatial neglect.

In a variety of neurological syndromes, patients may show tacit awareness of stimuli that cannot be consciously recollected or identified. Such dissociations are the defining characteristic of 'blindsight'; comparable phenomena are seen in some patients with amnesia and some with prosopagnosia, a profound impairment of familiar face recognition. We report here an analogous dissociation between overt and covert perception in a case of visuo-spatial neglect. The patient, P.S., had sustained right cerebral damage and failed overtly to process information in the hemispace contralateral to lesion. In common with most patients who manifest left-sided neglect, P.S. has a left homonymous hemianopia. Nonetheless, her neglect persists despite free movement of the head and eyes and is thus not a direct consequence of sensory loss in the left visual field. P.S. was presented simultaneously with two line drawings of a house, in one of which the left side was on fire. She judged that the drawings were identical; yet when asked to select which house she would prefer to live in, she reliably chose the house that was not burning.