Grasping Spatial Relationships: Failure to Demonstrate Allocentric Visual Coding in a Patient with Visual Form Agnosia

doi:10.1006/ccog.1998.0365

Consciousness and Cognition

Volume 7, Issue 3, September 1998, Pages 424-437

https://doi.org/10.1006/ccog.1998.0365 Get rights and content

The cortical visual mechanisms involved in processing spatial relationships remain subject to debate. According to one current view, the “dorsal stream” of visual areas, emanating from primary visual cortex and culminating in the posterior parietal cortex, mediates this aspect of visual processing. More recently, others have argued that while the dorsal stream provides egocentric coding of visual location for motor control, the separate “ventral” stream is needed for allocentric spatial coding. We have assessed the visual form agnosic patient DF, whose lesion mainly affects the ventral stream, on a prehension task requiring allocentric spatial coding. She was presented with transparent circular disks. Each disk had circular holes cut in it. DF was asked to reach out and grasp the disk by placing her fingers through the holes. The disks either had three holes (for forefinger, middle finger, and thumb) or two holes (for forefinger and thumb). The distance between the forefinger and thumb holes, and the orientation of the line formed by them, were independently varied. DF was quite unable to adjust her grip aperture or her hand orientation in the three-hole task. Although she was able to orient her hand appropriately for the two-hole disks, she still remained unable to adjust her grip aperture to the distance between the holes. These findings are consistent with the idea that allocentric processing of spatial information requires a functioning ventral stream, even when the information is being used to guide a motor response.

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: Address correspondence and reprint requests to: Dr. Chris Dijkerman, School of Psychology, University of St. Andrews, Fife, KY16 9JU, Scotland, UK. Fax: 01334-463042. E-mail:[email protected].

: M. A. Goodale

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Regular ArticleGrasping Spatial Relationships: Failure to Demonstrate Allocentric Visual Coding in a Patient with Visual Form Agnosia

Neuropsychologia

Trends in Neuroscience

Neuropsychologia

Neuropsychologia

Cortex

Cortical control of saccades and fixation in man. A PET study

Brain

Pathways for motion analysis: Cortical connections of the medial superior temporal and fundus of the superior temporal visual areas in the Macaque

The Journal of Comparative Neurology

Size illusion influences how we lift but not how we grasp an object

Experimental Brain Research

Object and spatial visual working memory activate separate neural systems in human cortex

Cerebral Cortex

The perception and prehension of objects oriented in the depth plane. I. Effects of visual form agnosia

Experimental Brain Research

Distributed hierarchical processing in the primate cerebral cortex

Cerebral Cortex

A neurological dissociation between perceiving objects and grasping them

Nature

The nature and limits of orientation and pattern processing supporting visuomotor control in a visual form agnosic

Journal of Cognitive Neuroscience

Age-related changes in cortical blood-flow activation during visual processing of faces and location

The Journal of Neuroscience

Functional anatomy of pointing and grasping in humans

Cerebral Cortex

Regular Article
Grasping Spatial Relationships: Failure to Demonstrate Allocentric Visual Coding in a Patient with Visual Form Agnosia