title: Vertical line quadrisection: "what" it represents and who gets the upper hand.
abstract: BACKGROUND
  Normal adults demonstrate a slight upward bias (vertical pseudoneglect) when attempting vertical line bisection. The mechanism for this bias is unknown. Activation of the allocentric (object-centered) ventral visual system during attempted bisection may induce this bias. This object-centered ventral stream may also mediate focal attention. As compared to bisection, when normal participants perform a vertical line quadrisection task that requires more focal attention, they may have a greater upward bias.
  
  
  METHODS
  Sixteen participants bisected and quadrisected vertical lines.
  
  
  RESULTS
  The mean upward bias (deviation error) for the quadrisection tasks was significantly higher than the mean error for the line bisections.
  
  
  CONCLUSIONS
  These results are consistent with the hypothesis that activation of the ventral stream by a task that requires focal allocentric attention can induce an upward vertical bias that is greater than the upward bias observed with allocentric line bisection, a task that requires more global attention.
authors.affiliation: Department of Neurology and Center for Neuropsychological Studies, University of Florida, Gainesville, FL, United States; Malcom Randall Veterans Affairs Medical Center, Gainesville, FL, United States. Electronic address: Adam.Falchook@neurology.ufl.edu.
authors.forename: Adam D
authors.initials: AD
authors.lastname: Falchook
authors.forename: Mayur D
authors.initials: MD
authors.lastname: Mody
authors.forename: A Benjamin
authors.initials: AB
authors.lastname: Srivastava
authors.forename: John B
authors.initials: JB
authors.lastname: Williamson
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Heilman
mesh_terms: D000328:Adult; D001288:Attention / Q000502:physiology*; D001921:Brain / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D013028:Space Perception / Q000502:physiology*; D055815:Young Adult