Article

A fundamental principle that has emerged from studies of natural gaze behavior is
that goal-directed arm movements are typically guided by a saccade to the target.
In this study, we evaluated a hypothesis that this principle does not apply to
rapid reach-to-grasp movements evoked by sudden unexpected balance perturbations.
These perturbations involved forward translation of a large
(2 x 6 m) motion
platform configured to simulate a "real-life" environment. Subjects performed a
common "daily-life" visuo-cognitive task (find a telephone and make a call) that
required walking to the end of the platform, which was triggered to move as they
approached a handrail mounted alongside the travel path. A deception was used to
ensure that the perturbation was truly unexpected. Eleven of 18 healthy
young-adult subjects (age 22-30) reached to grasp or touch the rail in response
to the balance perturbation. In support of the hypothesis, none of these arm
reactions was guided by concurrent visual fixation of the handrail. Seven of the
11 looked at the rail upon first entering the environment, and hence may have
used "stored" central-field information about the handrail location to guide the
subsequent arm reaction. However, the other four subjects never looked directly
at the rail, indicating a complete reliance on peripheral vision. These findings
add to previous evidence of distinctions in the CNS control of volitional and
perturbation-evoked arm movements. Future studies will determine whether similar
visuo-motor behavior occurs when the available handhold is smaller or when
subjects are not engaged in a concurrent visuo-cognitive task.
CI - Copyright (c) 2010 Elsevier B.V. All rights reserved.

Langue : ANGLAIS