Exploratory eye movements and visual hemi-neglect

The severity of visual hemineglect (VHN), as defined by a VHN Index from scores obtained on letter cancellation and visual matching tests, was compared to eye movement behavior during a visual searching task in a group of right-hemisphere stroke patients and a group of age-matched normal controls. A strong negative correlation was obtained between the VHN Index and eye movement Exploration Time of the left visuospatial field for the stroke patients, but not for the control subjects. Further analyses failed to discriminate Exploration Time performance of stroke patients with mild VHN from the performance of control subjects, but did discriminate stroke patients with marked VHN from each of these two groups. Covarying for the presence of a left-visual-field sensory defect slightly reduced the significance level of this finding. The results and questions raised by this study are discussed in the context of developing an operational definition for VHN using the method of directly monitoring eye movement.