Article

While the mechanisms of short-term adaptation to prism-altered apparent visual
direction have been widely investigated, the processes underlying adaptation to
prism-altered perceived distance are less well known. This study used a
hand-pointing paradigm and exposure with base-out prisms to evaluate the relative
contributions of sensory (visual and proprioceptive) and motor components of
adaptation to perceived-distance alteration. A main experiment was designed to
elicit adaptation at the sensory and motor levels, by giving subjects altered
visual feedback. A control experiment without visual feedback allowed the effects
of eye muscle potentiation (EMP) induced by sustained fixation through the prisms
to be uncovered. In the main experiment, the aftereffects were partitioned into
two-thirds visual and one-third motor, with no significant proprioceptive
component. These results differ from the classical pattern of short-term
adaptation to prism-altered apparent visual direction, which includes mainly
proprioceptive/motor adaptive components, with a smaller visual component. This
difference can be attributed to differences in accuracy between proprioception
and vision for localization in depth or in lateral directions. In addition, a
comparison of the visual aftereffects in the main and control experiments
revealed two sub-components with equal contributions: a recalibration of the
mapping between the vergence signal and perceived distance, and an EMP-related
aftereffect. These findings indicate that "visual" adaptation actually involves a
multiplicity of processes.
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Langue : ANGLAIS