Simulating unilateral neglect in normals using prism adaptation: implications for theory.
Rightward deviation on line bisection is considered one of the most classic clinical signs of unilateral visual neglect--a cognitive disorder of spatial processing that commonly follows right brain damage. Recently, short-term adaptation to wedge prisms has been shown to significantly reduce neglect on this and other conventional diagnostic tasks. Our previous study has shown that visuomotor adaptation in normals produces a similar pattern of directional bias on a line bisection task. Based on the good working knowledge of how neglect patients perform on different versions of the standard diagnostic task, we showed here that using leftward-deviating prisms in normals, it is possible to produce: (1) a reliable bias on line bisection, (2) a rightward specific deviation, (3) a modulation of rightward deviation, which depends on the relative spatial location of the target lines and (4) a line length effect. A final experiment confirmed that these after-effects are specific to prism adaptation rather than passive prism exposure. Collectively, these findings confirm that adaptation to left-deviating prisms in normals produces a reliable right-sided bias and as shown by a previous visuospatial judgement task, these findings cannot be adequately explained by the symmetric sensori-motor effects of prism adaptation. Taken together with the improvement of spatial neglect shown by right-deviating prisms only, the present study suggests that low level sensori-motor adaptations play a greater role in right hemisphere organisation for spatial cognition than previously thought.
Michel
Carine
C
Espace et Action, Institut National de la Santé et de la Recherche Médicale, Unité 534, Bron, France.
Pisella
Laure
L
Halligan
Peter W
PW
Luauté
Jacques
J
Rode
Gilles
G
Boisson
Dominique
D
Rossetti
Yves
Y
D000222:Adaptation, Physiological; D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D007909:Lenses; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D010468:Perceptual Disorders / Q000175:diagnosis / Q000503:physiopathology / Q000534:rehabilitation*; D010775:Photic Stimulation; D011597:Psychomotor Performance / Q000502:physiology*; D013028:Space Perception / Q000502:physiology; D014785:Vision, Ocular / Q000502:physiology; D014794:Visual Fields