Simulating unilateral neglect in normals using prism adaptation: implications for theory

Neuropsychologia. 2003;41(1):25-39. doi: 10.1016/s0028-3932(02)00135-5.

Abstract

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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptation, Physiological*
  • Adolescent
  • Adult
  • Analysis of Variance
  • Female
  • Functional Laterality / physiology
  • Humans
  • Lenses
  • Male
  • Middle Aged
  • Neuropsychological Tests
  • Perceptual Disorders / diagnosis
  • Perceptual Disorders / physiopathology
  • Perceptual Disorders / rehabilitation*
  • Photic Stimulation
  • Psychomotor Performance / physiology*
  • Space Perception / physiology
  • Vision, Ocular / physiology
  • Visual Fields