Bisection and visual exploration strategy in hemineglect: eye-movement measures for rehabilitation treatment

Aim of this study is to explore behavioral responses and eye movements of unilateral neglect patients in a virtual bisection task. Space to be bisected was included between two endpoint, segment length together with segment spatial dislocation were varied in order to test the presence of a “gradient effect” in both bisection behavior and visual exploration. Ten right neglect patients took part to the study, all data were then matched with those obtained from ten healthy participants. Behavioral measures (bisection and RTs) and eye-movements (fixation count and duration; first fixation count) were analyzed. Consistent spatial biases were found for bisection responses, RTs, fixation count and duration, as well as for the first fixation count. We then find a significant rightward bias in patients, i.e. increasing rightside bisection and rightward fixations when the stimuli were in the extreme left-position. Concerning merely segment length, we observed significant differences between-groups only for eye movement behavior, with increased rightward fixation count and duration in response to longer segments. In conclusion, “left-to-right” and “longer-to-shorter” continuous-gradient effects were not totally supported by our results, whereas an “extreme-left” gradient effect was suggested and discussed.