title: Effect of terminal accuracy requirements on temporal gaze-hand coordination during fast discrete and reciprocal pointings.
abstract: BACKGROUND
  Rapid discrete goal-directed movements are characterized by a well known coordination pattern between the gaze and the hand displacements. The gaze always starts prior to the hand movement and reaches the target before hand velocity peak. Surprisingly, the effect of the target size on the temporal gaze-hand coordination has not been directly investigated. Moreover, goal-directed movements are often produced in a reciprocal rather than in a discrete manner. The objectives of this work were to assess the effect of the target size on temporal gaze-hand coordination during fast 1) discrete and 2) reciprocal pointings.
  
  
  METHODS
  Subjects performed fast discrete (experiment 1) and reciprocal (experiment 2) pointings with an amplitude of 50 cm and four target diameters (7.6, 3.8, 1.9 and 0.95 cm) leading to indexes of difficulty (ID = log2[2A/D]) of 3.7, 4.7, 5.7 and 6.7 bits. Gaze and hand displacements were synchronously recorded. Temporal gaze-hand coordination parameters were compared between experiments (discrete and reciprocal pointings) and IDs using analyses of variance (ANOVAs).
  
  
  RESULTS
  Data showed that the magnitude of the gaze-hand lead pattern was much higher for discrete than for reciprocal pointings. Moreover, while it was constant for discrete pointings, it decreased systematically with an increasing ID for reciprocal pointings because of the longer duration of gaze anchoring on target.
  
  
  CONCLUSIONS
  Overall, the temporal gaze-hand coordination analysis revealed that even for high IDs, fast reciprocal pointings could not be considered as a concatenation of discrete units. Moreover, our data clearly illustrate the smooth adaptation of temporal gaze-hand coordination to terminal accuracy requirements during fast reciprocal pointings. It will be interesting for further researches to investigate if the methodology used in the experiment 2 allows assessing the effect of sensori-motor deficits on gaze-hand coordination.
authors.affiliation: Laboratoire de Physiologie de l'Exercice (E.A. 4338), Département STAPS, UFR CISM, Université de Savoie, 73376 Le Bourget du lac cedex, France. romain.terrier@univ-savoie.fr
authors.forename: Romain
authors.initials: R
authors.lastname: Terrier
authors.forename: Nicolas
authors.initials: N
authors.lastname: Forestier
authors.forename: Félix
authors.initials: F
authors.lastname: Berrigan
authors.forename: Mathieu
authors.initials: M
authors.lastname: Germain-Robitaille
authors.forename: Martin
authors.initials: M
authors.lastname: Lavallière
authors.forename: Normand
authors.initials: N
authors.lastname: Teasdale
mesh_terms: D000328:Adult; D000465:Algorithms; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D002138:Calibration; D003627:Data Interpretation, Statistical; D005133:Eye Movements / Q000502:physiology; D005403:Fixation, Ocular / Q000502:physiology*; D006225:Hand / Q000502:physiology*; D019416:Head Movements / Q000502:physiology; D006801:Humans; D008297:Male; D009068:Movement / Q000502:physiology*; D010775:Photic Stimulation; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time