Eye-movements during “virtual” grasping in unilateral neglect patient

Unilateral neglect is a neurological syndrome where patients show difficulties in perceiving, acting and focusing attention toward the controlesional perceptual hemifield. It has been suggested that different neural networks are involved in visual processing for action and perception, and that action-related mechanisms may be preserved in neglect syndrome. This study aims at exploring specific features of action-related visual behavior of neglect patients. We recorded eye-movements of patients and controls during a computerized bisection task implying a “virtual” grasping action. Participants imagined grasping an object between two spheres and had to mark where the object would be. The distance between the spheres differed in length (6 levels, from shorter to longer). Fixations count, fixations length and first fixation data of the clinical (3 participants) and control (10 participants) groups have been analyzed and statistically compared. We compared the present data with a previous study where we found a clear right-side bias in visual behavior of neglect patients (more and longer fixations in the right hemifield) during a perceptual gap bisection task. The bias was particularly significant when the gap was larger. In the present study, we have not found evidence for an analogous bias. When patients explored the visual field to make a “virtual” act, their visual behavior was quite similar to the controls’ one. The groups differed only in fixations count as a function of the gap length but without specific effects for right/left visual hemifields. These results will be discussed at the light of visual processing and attentional control theories to face the question of specific exploration strategies for perception and action.