Updating target location at the end of an orienting saccade affects the characteristics of simple point-to-point movements.
Six results are reported. (a) Reaching accuracy increases when visual capture of the target is allowed (e.g., target on vs. target off at saccade onset). (b) Whatever the visual condition, trajectories diverge only after peak acceleration, suggesting that accuracy is improved through feedback mechanisms. (c) Feedback corrections are smoothly implemented, causing the corrected and uncorrected velocity profiles to exhibit similar shapes. (d) Initial kinematics poorly predict final accuracy whatever the condition, indicating that target capture is not the only critical input for feedback control. (e) Hand and eye final variability are unrelated, suggesting that gaze direction is not a target signal for arm control. (f) Extent errors are corrected without modification of movement straightness; direction errors cause path curvature to increase. Together these data show that movements with straight paths and bell-shaped velocity profiles are not necessarily ballistic.
Desmurget
Michel
M
Institut National de la Santé et de la Recherche Médicale (INSERM), Bron, France. desmurget@lyon.inserm.fr
Turner
Robert S
RS
Prablanc
Claude
C
Russo
Gary S
GS
Alexander
Garret E
GE
Grafton
Scott T
ST
D000328:Adult; D005246:Feedback; D005260:Female; D006225:Hand; D006801:Humans; D008297:Male; D008875:Middle Aged; D009068:Movement; D011597:Psychomotor Performance; D012438:Saccades; D014796:Visual Perception