Controlling reaching movements during self-motion: Body-fixed versus earth-fixed targets

Etienne Guillaud, Martin Simoneau, Gabriel Gauthier, Jean Blouin
Motor Control. 2006-10-01; 10(4): 330-347
DOI: 10.1123/mcj.10.4.330

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1. Motor Control. 2006 Oct;10(4):330-47.

Controlling reaching movements during self-motion: body-fixed versus Earth-fixed

Guillaud E(1), Simoneau M, Gauthier G, Blouin J.

Author information:
(1)UMR Mouvement & Perception, CNRS et Universite de la Mediterranee, Marseille,

The control of goal-directed arm movements performed during whole-body
displacements is far from being understood. Recent studies suggested that the
compensatory arm movements that allow individuals to preserve hand-in-space
trajectory during unexpected body motion are controlled by sensorimotor,
automatic- like processes. We tested this hypothesis comparing both the accuracy
of movements directed towards body-fixed or Earth-fixed target during body
rotations and the amount of interference of the reaching tasks on a concurrent
cognitive task. Participants reached for a memorized 55 cm distant straight-ahead
target in darkness which was about 20 cm lower than the initial finger position.
The target was either body-fixed or Earth-fixed. At reaching onset, participants
could be rotated in yaw. The concurrent task consisted of a verbal reaction time
(RT) to an auditory stimulus. RTs increased when participants reached for the
target while they were rotated. However, this increase was not significantly
different for body-fixed and Earth-fixed targets. Reaching accuracy was greater
for body-fixed than for Earth-fixed targets. A control experiment suggested that
the errors in the Earth-fixed target condition arose from a difficulty in the
organization of movements which necessitate both the production of active forces
at the shoulder joint (to compensate for body rotation) and a concomitant
decrease of muscular activation to lower the arm during reaching movements. These
findings suggest that reaching for Earth-fixed or body-fixed targets during body
rotation cannot be considered as being purely automatic tasks.

DOI: 10.1123/mcj.10.4.330
PMID: 17293616 [Indexed for MEDLINE]

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