Head Movement Control in Visually Guided Tasks: Postural Goal and Optimality
K. Han Kim, R. Brent Gillespie and Bernard J. Martin
Submitted July 2005, Computers in Biology and Medicine
Abstract—This work investigates the control of horizontal head movements in the context of
unconstrained visually guided head and arm/finger aiming tasks. In a first experiment, the
head was free to move while gaze was directed at randomly presented eccentric targets
distributed horizontally (0 to 120°) at eye level. In a second experiment, the horizontal head
orientation was constrained to predetermined positions (0, 15, 30, 45 or 60° rightward)
while the right index finger aimed at targets with the arm fully extended. Kinematics of
head movements in gaze displacements exhibits an initial component weakly correlated
with target position, followed by multiple corrections. Since the eyes are assumed to
already be aimed at the target when the corrections occur, it is suggested that one goal of
head movement control is to achieve a desired final orientation (posture). This hypothesis is
supported by results from the second experiment that reveal an association between
eye/head orientation angles and errors exhibited in the visuo-spatial representation of the
environment. The minimization of error then underlies the control of head movement as a
postural response optimized for a given target and task condition.