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Role of eye, head, and shoulder geometry in the planning of accurate arm movements (2002)
| Venue: | Journal of Neurophysiology |
| Citations: | 8 - 1 self |
BibTeX
@ARTICLE{Henriques02roleof,
author = {D. Y. P. Henriques and J. D. Crawford},
title = {Role of eye, head, and shoulder geometry in the planning of accurate arm movements},
journal = {Journal of Neurophysiology},
year = {2002},
pages = {1677--1685}
}
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Abstract
shoulder geometry in the planning of accurate arm movements. J Neurophysiol 87: 1677–1685, 2002; 10.1152/jn.00509.2001. Eye-hand coordination requires the brain to integrate visual information with the continuous changes in eye, head, and arm positions. This is a geometrically complex process because the eyes, head, and shoulder have different centers of rotation. As a result, head rotation causes the eye to translate with respect to the shoulder. The present study examines the consequences of this geometry for planning accurate arm movements in a pointing task with the head at different orienta-tions. When asked to point at an object, subjects oriented their arm to position the fingertip on the line running from the target to the viewing eye. But this eye-target line shifts when the eyes translate with each new head orientation, thereby requiring a new arm pointing direction. We confirmed that subjects do realign their fingertip with the eye-target line during closed-loop pointing across various horizontal head orientations when gaze is on target. More importantly, subjects also showed this head-position–dependent pattern of pointing responses for the same paradigm performed in complete darkness. However, when gaze was not on target, compensation for these translations in the rotational centers partially broke down. As a result, subjects tended to overshoot the target direction relative to current gaze; perhaps explaining previously reported errors in aiming the arm to retinally peripheral targets. These results suggest that knowledge of head position signals and the resulting relative displacements in the centers of rotation of the eye and shoulder are incorporated using open-loop mechanisms for eye-hand coordination, but these transla-tions are best calibrated for foveated, gaze-on-target movements.
Keyphrases
accurate arm movement shoulder geometry head rotation complete darkness peripheral target open-loop mechanism arm position head-position dependent pattern different orienta-tions various horizontal head orientation relative displacement visual information current gaze continuous change eye-target line gaze-on-target movement target direction rotational center different center present study new head orientation pointing task head position signal eye-target line shift new arm pointing direction eye-hand coordination complex process
