title: Visual context modulates the subjective vertical in neglect: evidence for an increased rod-and-frame-effect.
abstract: Patients with spatial hemi-neglect display systematic deviations of the subjective vertical. The magnitude of such deviations was shown to be modulated by internal factors mediating the perception of verticality, including head-orientation. The present study investigated whether and how spatial orientation deficits are modulated by external, contextual changes in neglect patients. In a classic rod-and-frame task, we analyzed effects of frame orientation on the subjective visual vertical (SVV) in neglect patients, control patients with left- or right-sided brain damage without neglect and healthy participants. We found that neglect patients, but not brain-damaged control patients, generally display a systematic counterclockwise (CCW) tilt in their SVV judgments. Furthermore, all participant groups displayed a typical rod-and-frame effect (RFE), that is, a modulation of the SVV as a function of frame tilt. However, in the control groups, this modulation was only moderate whereas in the neglect group SVV judgments were substantially and systematically modulated by frame orientation: with CCW frame tilts, the spatial bias of neglect patients increased as a function of the magnitude of the tilt whereas with clockwise (CW) frame tilts, the spatial bias was decreased in case of moderate frame tilts and even reversed in case of stronger frame tilts, resulting in a substantial CW spatial bias. This dramatically enhanced RFE might be caused by a pathologically increased influence of contextual cues on the subjective vertical in neglect patients as a consequence of impaired processing of gravitational information. The results indicate a systematic bias of the subjective vertical along with an impairment of spatial orientation constancy which leads to severe perturbations of subjective space as well as an increased reliance on internal and external cues mediating the perception of verticality in neglect.
authors.affiliation: Department of Psychology, General and Experimental Psychology/Neuro-cognitive Psychology, Ludwig Maximilian University, Leopoldstrasse 13, D-80802 Munich, Germany. Johanna.Funk@psy.lmu.de
authors.forename: J
authors.initials: J
authors.lastname: Funk
authors.forename: K
authors.initials: K
authors.lastname: Finke
authors.forename: H J
authors.initials: HJ
authors.lastname: Müller
authors.forename: K S
authors.initials: KS
authors.lastname: Utz
authors.forename: G
authors.initials: G
authors.lastname: Kerkhoff
mesh_terms: D000328:Adult; D000368:Aged; D001921:Brain / Q000503:physiopathology*; D003463:Cues; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010468:Perceptual Disorders / Q000209:etiology / Q000503:physiopathology*; D010775:Photic Stimulation; D013028:Space Perception / Q000502:physiology*; D020521:Stroke / Q000150:complications / Q000503:physiopathology