A paradoxical improvement of misreaching in optic ataxia: new evidence for two separate neural systems for visual localization

A D Milner, Y Paulignan, H C Dijkerman, F Michel, M Jeannerod

Research output: Contribution to journalArticlepeer-review

173 Citations (Scopus)

Abstract

We tested a patient (A. T) with bilateral brain damage to the parietal lobes, whose resulting 'optic ataxia' causes her to make large pointing errors when asked to locate single light emitting diodes presented in her visual field. We report here that, unlike normal individuals, A. T's pointing accuracy improved when she was required to wait for 5s before responding. This counter-intuitive result is interpreted as reflecting the very brief time-scale on which visuomotor control systems in the superior parietal lobe operate. When an immediate response was required, A. T's damaged visuomotor system caused her to make large errors; but when a delay was required, a different, more flexible, visuospatial coding system-presumably relatively intact in her brain-came into play, resulting in much more accurate responses. The data are consistent with a dual processing theory whereby motor responses made directly to visual stimuli are guided by a dedicated system in the superior parietal and premotor cortices, while responses to remembered stimuli depend on perceptual processing and may thus crucially involve processing within the temporal neocortex.

Original languageEnglish
Pages (from-to)2225-2229
Number of pages5
JournalProceedings of the Royal Society of London Series B: Biological Sciences
Volume266
Publication statusPublished - 7 Nov 1999

Keywords

  • optic ataxia
  • parietal lobe
  • visuomotor control
  • spatial localization
  • POSTERIOR PARIETAL CORTEX
  • MOTOR REPRESENTATIONS
  • GRASPING MOVEMENTS
  • FORM AGNOSIA
  • SPACE
  • INFORMATION
  • PERCEPTION
  • PATIENT
  • VISION
  • HAND

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