Supra-spinal circuits shape inhibitory postural adjustments anticipating voluntary index-finger flexion |
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Authors: | Bourrelly Aurore Bringoux Lionel Vercher Jean-Louis |
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Institution: | (1) Institute of Movement Sciences “Etienne-Jules Marey”, UMR 6233 CNRS and Université de la Méditerranée, 163, avenue de Luminy CP 910, 13288 Marseille Cedex 9, France |
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Abstract: | We investigated the influence of gaze elevation on judging the possibility of passing under high obstacles during pitch body
tilts, while stationary, in absence of allocentric cues. Specifically, we aimed at studying the influence of egocentric references
upon geocentric judgements. Seated subjects, orientated at various body orientations, were asked to perceptually estimate
the possibility of passing under a projected horizontal line while keeping their gaze on a fixation target and imagining a
horizontal body displacement. The results showed a global overestimation of the possibility of passing under the line, and
confirmed the influence of body orientation reported by Bringoux et al. (Exp Brain Res 185(4):673–680, 2008). More strikingly, a linear influence of gaze elevation was found on perceptual estimates. Precisely, downward eye elevation
yielded increased overestimations, and conversely upward gaze elevation yielded decreased overestimations. Furthermore, body
and gaze orientation effects were independent and combined additively to yield a global egocentric influence with a weight
of 45 and 54%, respectively. Overall, our data suggest that multiple egocentric references can jointly affect the estimated
possibility of passing under high obstacles. These results are discussed in terms of “interpenetrability” between geocentric
and egocentric reference frames and clearly demonstrate that gaze elevation is involved, as body orientation, in geocentric
spatial localization. |
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Keywords: | Spatial localization Reference frames Gaze elevation Body orientation Egocentric Geocentric |
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