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- Peter W. Halligan & John C. Marshall (1998). Neglect of Awareness. Consciousness and Cognition 7 (3):356-380.We describe some of the signs and symptoms of left visuo-spatial neglect. This common, severe and often long-lasting impairment is the most striking consequence of right hemisphere brain damage. Patients seem to (over-)attend to the right with subsequent inability to respond to stimuli in contralesional space. We draw particular attention to how patients themselves experience neglect. Furthermore, we show that the neglect patient's loss of awareness of left space is crucial to an understanding of the condition. Even after left space has been brought into the patient's consciousness (either by local cueing on the left or by an emphasis on global properties of the scene as a whole), this awareness of left space rapidly declines. We suggest that much of the symptomology of left neglect can be interpreted as a disconnection between brain mechanisms that are relatively specialized for local (detail) visual processing and global (panoramic) processing. This failure of communication between functional (subpersonal) mechanisms then has consequences for how perceptual and representational content enters into awareness. Failure of the local contents of left space to be consciously accessed is, in turn, an important aspect of why left neglect is so difficult to remediate. Patients can ''know'' that they have neglect but are cut off from the perceptual awareness that would enable them to overcome their attentional bias to the right.In my reading list | Discuss this article | Edit | Categorize |My bibliography
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Ninety-one right brain-damaged patients with left neglect and 43 right brain-damaged patients without neglect were asked to extend horizontal segments, either left- or rightward, starting from their right or left endpoints, respectively. Earlier experiments based on similar tasks had shown, in left neglect patients, a tendency to overextend segments toward the left side. This seemingly paradoxical phenomenon was held to undermine current explanations of unilateral neglect. The results of the present extensive research demonstrate that contralesional overextension is also evident in (...)
Patients may show a more-or-less complete deviation of the head and eyes towards the right (ipsilesional) side [that is, to the same side of egocentric space as the brain lesion responsible for their disorder]. If addressed by the examiner from the left (contralesional) side [the opposite side to their lesion], patients with severe extrapersonal neglect may fail to respond or may look for the speaker in the right side of the room, turning head and eyes more and more to the (...)
Right brain-damaged patients with unilateral neglect, who ignore left-sided visual events, may also omit left-sided details when describing known places from memory. Modulating the orienting of visual attention may ameliorate imaginal neglect. A first step toward explaining these phenomena might be to postulate that space-related imagery is a cognitive activity involving attentional and intentional aspects.
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When left-neglect patients are required to extend horizontal segments to double their original length, relative left overextension is frequently observed. Less frequently, relative left underextension may also be found. It was hypothesized that this contrast could depend on the degree of horizontal anisometry of the medium for the representation of spatial properties. The present paper reports an experiment conducted in order to test that hypothesis, on the basis of which left overextension should be larger with shorter than with longer segments (...)
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| Discuss this article | Edit | Categorize | My bibliography | Export citation | Other links: labnic.unige.ch psychology.nottingham.ac.uk icn.ucl.ac.uk ncbi.nlm.nih.gov ingentaconnect.com | Scholar | More..
| | Other links: labnic.unige.ch psychology.nottingham.ac.uk icn.ucl.ac.uk ncbi.nlm.nih.gov ingentaconnect.com | Scholar | More.. In my reading list
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| | Other links: ncbi.nlm.nih.gov linkinghub.elsevier.com | Scholar | More.. Unilateral neglect stems from a relatively selective impairment of exogenous, or stimulus-related, orienting of attention. This neuropsychological evidence parallels “change blindness” experiments, in which normal individuals lack awareness of salient details in the visual scene as a consequence of their attention being exogenously attracted by a competing event, suggesting that visual consciousness requires the integrity of exogenous orienting of attention.
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