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Vertical gaze angle as a distance cue for programming reaching: insights from visual form agnosia II (of III)

Mon-Williams, M., McIntosh, R.D. and Milner, A.D. (2001) Vertical gaze angle as a distance cue for programming reaching: insights from visual form agnosia II (of III). Experimental Brain Research, 139 (2). pp. 137-142. ISSN 0014-4819

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Abstract

It has been shown that a patient with visual form agnosia (DF) relies predominantly on vergence information when gauging target distance in an open-loop pointing task. This finding suggested that the programming of prehension might be severely disrupted if DF viewed target objects through ophthalmic prisms. An initial experiment showed that this prediction was not upheld; DF was able to programme reasonably accurate movements to objects located on a tabletop despite large changes in vergence angle. A second experiment, however, showed that placing the target objects at eye height whilst manipulating vergence angle caused gross disruption to prehension, with DF mis-programming the reach component in a predictable manner. Notably, the evidence for DF's reliance on vergence distance information was obtained in a task where the targets were viewed at eye height. These experiments indicate that DF uses vertical gaze angle to gauge target distance in normal prehension and suggest that this extra-retinal cue may be a useful source of distance information for the human nervous system, especially where pictorial cues are impoverished.

Item Type: Article
Keywords: prehension; binocular; vergence; distance perception; human
Institution: The University of Leeds
Academic Units: The University of Leeds > Faculty of Medicine and Health (Leeds) > Institute of Psychological Sciences (Leeds) > Cognitive Psychology (Leeds)
Depositing User: Repository Officer
Date Deposited: 19 Jun 2009 11:11
Last Modified: 29 Sep 2010 14:24
Published Version: http://dx.doi.org/10.1007/s002210000658
Status: Published
Publisher: Springer Verlag
Identification Number: 10.1007/s002210000658
URI: http://eprints.whiterose.ac.uk/id/eprint/8678

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