Article

Among the many dissociations describing the visual system, the dual theory of two
visual systems, respectively dedicated to perception and action, has yielded a
lot of support. There are psychophysical, anatomical and neuropsychological
arguments in favor of this theory. Several behavioral studies that used sensory
and motor psychophysical parameters observed differences between perceptive and
motor responses. The anatomical network of the visual system in the non-human
primate was very readily organized according to two major pathways, dorsal and
ventral. Neuropsychological studies, exploring optic ataxia and visual agnosia as
characteristic deficits of these two pathways, led to the proposal of a
functional double dissociation between visuomotor and visual perceptual
functions. After a major wave of popularity that promoted great advances,
particularly in knowledge of visuomotor functions, the guiding theory is now
being reconsidered. Firstly, the idea of a double dissociation between optic
ataxia and visual form agnosia, as cleanly separating visuomotor from visual
perceptual functions, is no longer tenable; optic ataxia does not support a
dissociation between perception and action and might be more accurately viewed as
a negative image of action blindsight. Secondly, dissociations between perceptive
and motor responses highlighted in the framework of this theory concern a very
elementary level of action, even automatically guided action routines. Thirdly,
the very rich interconnected network of the visual brain yields few arguments in
favor of a strict perception/action dissociation.
Overall, the dissociation
between motor function and perceptive function explored by these behavioral and
neuropsychological studies can help define an automatic level of action
organization deficient in optic ataxia and preserved in action blindsight, and
underlines the renewed need to consider the perception-action circle as a
functional ensemble.
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Langue : ANGLAIS