title: Ipsilateral neglect: reversal of bias or exaggerated cross-over phenomenon?
abstract: When right brain injury produces contralesional neglect (CN), patients typically misbisect lines to the right. However, others demonstrate so-called "ipsilateral neglect" (IN) with misbisection to the left of midpoint. Paradoxically, most patients with CN also demonstrate a 'cross-over' phenomenon whereby they misbisect short lines to the left. It is not known whether patients with IN actually have a contralesional bias opposite the ipsilesional bias observed with CN, or if their performance reflects an exaggerated cross-over. These alternatives can be distinguished by power function analysis which evaluates the relationship between magnitude of perception and stimulus magnitude. Using line bisection tasks to derive a power function, an IN patient showed a reduced exponent (beta = 0.841), falling outside 95% confidence intervals (CI) for controls but within the CI for CN patients. The IN patient showed a greatly increased constant (K = 7.82), extending outside the CI for both controls and CN patients. The results suggest that the anomalous leftward misbisection with IN is associated with an exaggerated cross-over point and not simply reversal of spatial bias.
authors.affiliation: Department of Neurology, University of New Mexico Health Sciences Center, USA. Adair.John@Albuquerque.VA.Gov
authors.forename: J C
authors.initials: JC
authors.lastname: Adair
authors.forename: A
authors.initials: A
authors.lastname: Chatterjee
authors.forename: R L
authors.initials: RL
authors.lastname: Schwartz
authors.forename: K M
authors.initials: KM
authors.lastname: Heilman
mesh_terms: D000328:Adult; D002544:Cerebral Infarction / Q000000981:diagnostic imaging / Q000523:psychology*; D003072:Cognition Disorders / Q000000981:diagnostic imaging / Q000523:psychology*; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests; D014057:Tomography, X-Ray Computed