EYE-MOVEMENTS AND ORIENTING OF ATTENTION IN PATIENTS WITH VISUAL NEGLECT

The aim of the present study was to assess the relationship between ov ert and covert orienting of attention in visual neglect patients with parietal and fronto-parietal lesions. Two stimuli were presented at ec centricities of 8 degrees or 20 degrees to the left (LVF) or right (RV F) visual fields and the patient was required to maintain fixation on the central mark and to respond only manually upon the appearance of t he stimulus. Neglect patients with fronto-parietal lesion showed a lac k of oculomotor control and the presence of leftward eye movements wit hout corresponding attentional shifts. Neglect patients with parietal lesions did not show this phenomenon. They rarely responded ocularly a nd manually to LVF stimuli, whereas they were unable to inhibit an aut omatic ocular orienting reaction towards RVF stimuli. When a RVF stimu li triggered both ocular and attentional shifts, the pattern of respon ses revealed a retinal eccentricity effect. Patients were more accurat e to respond to stimuli located at 8 degrees than 20 degrees. In contr ast, when a RVF stimuli triggered only attentional shifts, the results showed the attentional gradient effect (Ladavas, 1990). Patients were more accurate to respond to stimuli located at 20 degrees than 8 degr ees. Therefore,the results of the present study seem to suggest a func tional dissociation of the mechanisms subserving attentional and gaze orienting and a differential role played by the frontal and parietal l obes in overt visual orienting.