title: Is "left" always where the thumb is right?: stimulus-response compatibilities as a function of posture and location of the responding hand.
abstract: OBJECTIVE
  To determine hand-centered coordinate systems for left-right discriminations in representational space, including scenes imagined behind one's head ("backspace").
  
  
  METHODS
  Thirty-two healthy men responded with the index or ring finger of their right (dominant) hand to numbers presented in the center of a screen. These indicated hours on the right or left half of a clock face. A decision "earlier or later than six o'clock?" was required. There were 4 response conditions: (1) pronated and (2) supinated hand in frontspace and (3) pronated and (4) supinated hand in backspace.
  
  
  RESULTS
  "Left" and "right" were reliably and differentially associated with the 2 different fingers for all conditions except the pronated hand in backspace (conflict between body-centered and hand-centered reference frames). When backspace trials were analyzed as a function of individual strategies of the localization of the imaginary clockface (ie, around the stimulus number in frontspace versus around the response hand in backspace), it was found that the 2 strategies were associated with opposite right/left assignments.
  
  
  CONCLUSIONS
  Together, these results indicate relatively universal left/right assignments to the fingers of a hand held in canonical postures and interindividually variable (but intraindividually consistent) assignments for less canonical postures. The task appears suitable for the quantification of representational neglect, especially in backspace.
authors.affiliation: Department of Neuropsychology Unit, University Hospital Zurich, CH-8091 Zurich, Switzerland.
authors.forename: Jürg
authors.initials: J
authors.lastname: Leuthard
authors.forename: Daniel
authors.initials: D
authors.lastname: Bächtold
authors.forename: Peter
authors.initials: P
authors.lastname: Brugger
mesh_terms: D000328:Adult; D005385:Fingers / Q000502:physiology; D007839:Functional Laterality / Q000502:physiology*; D006225:Hand / Q000502:physiology*; D006801:Humans; D007092:Imagination / Q000502:physiology; D008297:Male; D011187:Posture / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology; D013028:Space Perception / Q000502:physiology; D013933:Thumb / Q000502:physiology*