Misrepresentation of horizontal space in left unilateral neglect

Abstract

Background: Right-brain–damaged patients with left unilateral neglect are reported to misperceive the horizontal extension of contralesional stimuli as being shorter than that of ipsilesional stimuli.Objective: To investigate the functional and anatomic correlates of horizontal space misrepresentation.Methods: Eight right-brain–damaged patients with contralesional neglect and complete hemianopia (N+H+), nine right-brain–damaged patients with contralesional neglect and no visual field defect (N+H−), and five unilateral brain-damaged patients with contralesional complete hemianopia and no neglect (N−H+) reproduced a horizontal distance (10 cm) in the contralesional and ipsilesional hemispace.Results: N+H+ patients overextended the distance contralesionally and underextended the same distance ipsilesionally. N+H− and N−H+ patients reproduced equivalent distances contralesionally and ipsilesionally. Compared with N+H− patients, N+H+ patients had a greater ipsilesional shift when bisecting horizontal lines; however, these two groups of patients had comparable neglect severity on multiple-item cancellation tasks. In the N+H+ group the area of maximal overlapping of the lesion was in the posterior cerebral lobes.Conclusion: Complete contralesional hemianopia after posterior brain damage is an important factor in determining misrepresentation of horizontal space in patients with left unilateral neglect.