title: Allocentric But Not Egocentric Pseudoneglect of Peripersonal Space.
abstract: OBJECTIVE
  Healthy adults often deviate leftward on line bisection tasks (allocentric pseudoneglect) but rightward on body part bisection tasks (egocentric pseudoneglect). People visually estimate distance in peripersonal space by comparing the distance to the length of a body part such as an arm's length (an egocentric reference) or using standard units of distance such as inches (an allocentric reference). Our objective was to learn whether people have pseudoneglect when estimating distances in peripersonal space using egocentric versus allocentric reference frames.
  
  
  METHODS
  Twelve healthy participants standing either next to or 5 feet away from a wall were asked to move away from or toward the wall such that their shoulder would be what they judged to be an arm's length or a distance of 1, 2, or 3 feet from the wall.
  
  
  RESULTS
  The participants estimated their arm's length more accurately than the standard units of distance (possibly related to learning and practice). Participants were more precise when estimating the length of their left than their right arm. When estimating standard units of distance, participants underestimated the distances on their left side more than on their right.
  
  
  CONCLUSIONS
  Our results support the postulate that left pseudoneglect is an allocentric phenomenon related to a hemispheric asymmetry in computing allocentric distances. The participants underestimated 2 and 3 feet, but overestimated 1 foot. This dichotomy may relate to using focused versus distributed attention. The brain mechanisms leading to these asymmetries remain to be determined.
authors.affiliation: *Center for Neuropsychological Studies, Department of Neurology, University of Florida College of Medicine, Gainesville, Florida †Department of Neurology, University of South Florida Morsani College of Medicine, Tampa, Florida ‡Malcom Randall Veterans Affairs Medical Center, Gainesville, Florida.
authors.forename: Tigran
authors.initials: T
authors.lastname: Kesayan
authors.forename: John B
authors.initials: JB
authors.lastname: Williamson
authors.forename: Adam D
authors.initials: AD
authors.lastname: Falchook
authors.forename: Frank M
authors.initials: FM
authors.lastname: Skidmore
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Heilman
mesh_terms: D000368:Aged; D001288:Attention; D003071:Cognition / Q000502:physiology*; D004215:Distance Perception / Q000502:physiology*; D005260:Female; D006801:Humans; D007858:Learning; D008297:Male; D008875:Middle Aged; D010468:Perceptual Disorders / Q000503:physiopathology*; D012649:Self Concept; D013028:Space Perception / Q000502:physiology