Delay abolishes the obstacle avoidance deficit in unilateral optic ataxia

N. J. Rice, Martin G. Edwards, I. Schindler, T. D. Punt, R. D. McIntosh, G. W. Humphreys, V. Lestou, A. D. Milner

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

Optic ataxic patients have deficits in the visual control of manual reaching and grasping. It has been established previously that these deficits in target-directed behaviour improve following a delay in response. Recently it has been demonstrated that optic ataxic patients also have deficits in taking potential obstacles into account during reaching. The present study was therefore designed to test whether delay would bring an improvement in this behaviour as well. We present experimental data from a patient with unilateral optic ataxia (M.H.). First we document M.H.'s pointing errors, which show a reliable pattern of impairment when pointing to targets in his right visual field, particularly when using his right hand. We then show that a similar pattern of deficits is observable in his ability to negotiate between non-targets: that is, M.H. selectively fails to take account of obstacles in his right visual field, but only while reaching with his right hand. Finally we demonstrate that this obstacle avoidance deficit disappears following a 5 s delay in response: under these conditions M.H. now takes account of both non-target objects with either hand. The results are interpreted within the 'two visual streams' model of cortical visual processing. (C) 2008 Elsevier Ltd. All rights reserved.
Original languageEnglish
Pages (from-to)1549-1557
Number of pages9
JournalNeuropsychologia
Volume46
Issue number5
DOIs
Publication statusPublished - 2008

Keywords / Materials (for Non-textual outputs)

  • visuomotor behaviour
  • Optic ataxia
  • Reaching
  • Dorsal stream
  • Two visual systems

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