Impaired search for orientation but not color in hemi-spatial neglect

Patients with hemi-spatial neglect have trouble finding targets defined by a conjunction of visual features. The problem is widely believed to stem from a high-level deficit in attentional deployment, which in turn has led to disagreement over whether the detection of basic features is also disrupte...

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Bibliographic Details
Published in:Cortex 2008, Vol.44 (1), p.68-78
Main Authors: Wilkinson, David, Ko, Philip, Milberg, William, McGlinchey, Regina
Format: Article
Language:English
Subjects:
Aged
Attention
Color Perception
Discrimination (Psychology)
Feature detection
Female
Humans
Male
Middle Aged
Orientation
Perception
Perceptual Disorders - diagnosis
Perceptual Disorders - physiopathology
Photic Stimulation
Reaction Time
Recognition (Psychology)
Space Perception
Unilateral neglect
Visual Fields
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Summary:Patients with hemi-spatial neglect have trouble finding targets defined by a conjunction of visual features. The problem is widely believed to stem from a high-level deficit in attentional deployment, which in turn has led to disagreement over whether the detection of basic features is also disrupted. If one assumes that the detection of salient visual features can be based on the output of spared ‘preattentive’ processes (Treisman and Gelade, 1980), then feature detection should remain intact. However, if one assumes that all forms of detection require at least a modicum of focused attention (Duncan and Humphreys, 1992), then all forms of search will be disrupted to some degree. Here we measured the detection of feature targets that were defined by either a unique color or orientation. Comparable detection rates were observed in non-neglected space, which indicated that both forms of search placed similar demands on attention. For either of the above accounts to be true, the two targets should therefore be detected with equal efficiency in the neglected field. We found that while the detection rate for color was normal in four of our five patients, all showed an increased reaction time and/or error rate for orientation. This result points to a selective deficit in orientation discrimination, and implies that neglect disrupts specific feature representations. That is, the effects of neglect on visual search are not only attentional but also perceptual.
ISSN:0010-9452
1973-8102
DOI:10.1016/j.cortex.2005.10.001