Preserved prism adaptation in bilateral optic ataxia: strategic versus adaptive reaction to prisms.

L. Pisella, C. Michel, H. Gr�a, C. Tilikete, A. Vighetto, Y. Rossetti
Experimental Brain Research. 2004-06-01; 156(4): 399-408
DOI: 10.1007/s00221-003-1746-4

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https://www.bordeaux-neurocampus.fr/12294

1. Exp Brain Res. 2004 Jun;156(4):399-408. doi: 10.1007/s00221-003-1746-4. Epub
2004 May 5.

Preserved prism adaptation in bilateral optic ataxia: strategic versus adaptive
reaction to prisms.

Pisella L(1), Michel C, Gréa H, Tilikete C, Vighetto A, Rossetti Y.

Author information:
(1)Espace et Action, Institut National de la Santé et de la Recherche Médicale,
Unité 534, 16 avenue Lépine, Case 13, 69676 Bron, France.

To date the anatomical substrate(s) of prism adaptation remain(s) particularly
debated, with two main candidates emerging from the literature: the posterior
parietal cortex (PPC) and the cerebellum. The functional processes involved in
the acquisition of the adaptive aftereffects also remain largely unknown. The
main result shown here is that a patient with a bilateral optic ataxia can adapt
to an optical deviation, which allows us to make a step forward on these two
issues. First, it demonstrates that the corresponding part of the PPC is not a
necessary substrate for prism adaptation. Second, since this patient exhibits
deficit for fast visuo-motor guidance, it provides direct evidence for a
dissociation between on-line visuo-motor control and visuo-motor plasticity.
Since the intermanual transfer rate of adaptation is larger in this patient than
in control subjects, the PPC may still have an influence on adaptation under
normal conditions. We propose a model of the relative contribution of the PPC
and the cerebellum during prism exposure, associating these two structures with
the two interacting behavioural components of prism adaptation described by
previous psychophysical experiments: the strategic component would be linked to
the PPC and the adaptive component to the cerebellum. In this model, the
strategic component enters in conflict with the development and the
generalisation of the adaptive aftereffects. This idea is compatible with the
fact that a lesion of the PPC increases the transfer rate and the generalisation
of the adaptation, as is also observed in unilateral neglect.