Neglect of Awareness

doi:10.1006/ccog.1998.0362

Consciousness and Cognition

Volume 7, Issue 3, September 1998, Pages 356-380

https://doi.org/10.1006/ccog.1998.0362 Get rights and content

Abstract

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.

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The active construction of the visual world
2017, Neuropsychologia
Citation Excerpt :
These mechanisms can fail in the damaged brain, and a common syndrome resulting from this failure is spatial hemineglect. Patients suffering from this fail to attend to one side (typically the left) of visual space (Halligan and Marshall, 1998). One manifestation of this attentional deficit is a decreased frequency of saccadic sampling in the neglected half of space relative to the other (Karnath and Rorden, 2012).
What we see is fundamentally dependent on where we look. Despite this seemingly obvious statement, many accounts of the neurobiology underpinning visual perception fail to consider the active nature of how we sample our sensory world. This review offers an overview of the neurobiology of visual perception, which begins with the control of saccadic eye movements. Starting from here, we can follow the anatomy backwards, to try to understand the functional architecture of neuronal networks that support the interrogation of a visual scene. Many of the principles encountered in this exercise are equally applicable to other perceptual modalities. For example, the somatosensory system, like the visual system, requires the sampling of data through mobile receptive epithelia. Analysis of a somatosensory scene depends on what is palpated, in much the same way that visual analysis relies on what is foveated. The discussion here is structured around the anatomical systems involved in active vision and visual scene construction, but will use these systems to introduce some general theoretical considerations. We will additionally highlight points of contact between the biology and the pathophysiology that has been proposed to cause a clinical disorder of scene construction – spatial hemineglect.
Neural correlates of visuospatial consciousness in 3D default space: Insights from contralateral neglect syndrome
2014, Consciousness and Cognition
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The most common damage leading to hemispatial neglect is a legion in the right parietal lobe leading to visual neglect of the left side of the visual field (Kerkhoff, 2001). These patients will bump into objects or obstacles on their left side (Unsworth, 2007), if asked to draw an object they will draw only the right side (Kerkhoff, 2001), they may read only the right pages of books (Halligan & Marshall, 1998), or they may neglect the left side of their body (Kerkhoff, 2001). Some researchers propose that the right superior temporal gyrus is associated with hemineglect but this has been challenged (Mort et al., 2003) and remains controversial.
One of the most compelling questions still unanswered in neuroscience is how consciousness arises. In this article, we examine visual processing, the parietal lobe, and contralateral neglect syndrome as a window into consciousness and how the brain functions as the mind and we introduce a mechanism for the processing of visual information and its role in consciousness. We propose that consciousness arises from integration of information from throughout the body and brain by the thalamus and that the thalamus reimages visual and other sensory information from throughout the cortex in a default three-dimensional space in the mind. We further suggest that the thalamus generates a dynamic default three-dimensional space by integrating processed information from corticothalamic feedback loops, creating an infrastructure that may form the basis of our consciousness. Further experimental evidence is needed to examine and support this hypothesis, the role of the thalamus, and to further elucidate the mechanism of consciousness.
Visual Neglect
2012, Encyclopedia of Human Behavior: Second Edition
Visual neglect is a debilitating medical condition has attracted the interest of clinicians and neuroscientists given its frequency (25–30% of right hemisphere strokes), significant impact on health and rehabilitation services, and providing neuropsychological insights for human visual perception, visuo-motor control, and spatial attention. Viewed as a deficit in attention, intention, global–local processing, spatial memory, and mental representation, neglect has been shown to result from the interplay of damage to several different neurocognitive systems (particularly posterior parietal cortex) involved in conscious awareness, many of which share little in common other than a contralesional gradient of increasing impairment, with comparatively well-preserved performance on the ipsilesional side of space.
Shifting attention in viewer- and object-based reference frames after unilateral brain injury
2011, Neuropsychologia
Citation Excerpt :
A common problem following unilateral brain injury is an inability to orient or attend to items appearing on the contralesional side of space (Driver & Vuilleumier, 2001; Halligan & Marshall, 1998; Heilman & Valenstein, 1979; Rafal, 1994).
The aims of the present study were to investigate the respective roles that object- and viewer-based reference frames play in reorienting visual attention, and to assess their influence after unilateral brain injury. To do so, we studied 16 right hemisphere injured (RHI) and 13 left hemisphere injured (LHI) patients. We used a cueing design that manipulates the location of cues and targets relative to a display comprised of two rectangles (i.e., objects). Unlike previous studies with patients, we presented all cues at midline rather than in the left or right visual fields. Thus, in the critical conditions in which targets were presented laterally, reorienting of attention was always from a midline cue. Performance was measured for lateralized target detection as a function of viewer-based (contra- and ipsilesional sides) and object-based (requiring reorienting within or between objects) reference frames. As expected, contralesional detection was slower than ipsilesional detection for the patients. More importantly, objects influenced target detection differently in the contralesional and ipsilesional fields. Contralesionally, reorienting to a target within the cued object took longer than reorienting to a target in the same location but in the uncued object. This finding is consistent with object-based neglect. Ipsilesionally, the means were in the opposite direction. Furthermore, no significant difference was found in object-based influences between the patient groups (RHI vs. LHI). These findings are discussed in the context of reference frames used in reorienting attention for target detection.
Disruption of spatial memory in visual search in the left visual field in patients with hemispatial neglect
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Spatial working memory during an ongoing visual search trial was tested in both visual fields for right-brain damaged patients with contralesional spatial neglect, as well as age-matched control patients with right-hemisphere lesions but no neglect. We examined within-trial spatial memory by using a relocation search paradigm introduced by Kristjansson (2000) (modified from Horowitz & Wolfe, 1998), in which the display items traded places every 110 ms so that the target was never to be found in the same location from one moment to the next (the relocation condition), as compared with a static condition where the display items remained in place for the whole trial duration. To equate appearance between the two conditions, all items changed orientation every 110 ms in both conditions, and were masked after each of the briefly presented visual arrays. The results showed that search was disrupted by item relocation for both patients and controls, but importantly this disruption was only seen in the right visual field for the patients, not the left, indicating that their spatial working memory in left visual space is already severely disrupted, and to a greater degree than for their right visual space, in contrast to what has been previously argued.
The left hemisphere does not miss the right hemisphere
2009, The Neurology of Consciousness

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^☆: Reprint requests should be addressed to Dr. Peter W. Halligan, Rivermead Rehabilitation Centre, Abingdon Road, Oxford OX1 4XD, UK. This work was supported by the British Medical Research Council, the Stroke Association, and the McDonnell-Pew Foundation.

^☆☆: A. D. MilnerM. D. Rugg

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Regular ArticleNeglect of Awareness☆,☆☆

Abstract

Perceptual and conceptual processes in a case of left sided spatial inattention

Perceptual and Motor Skills

Visual processing without awareness: Evidence from unilateral neglect

Journal of Cognitive Neuroscience

Understanding consciousness: Clues from unilateral neglect and related disorders

The neuropsychology of consciousness

Unilateral neglect of representational space

Cortex

Breakdown of perceptual awareness in unilateral neglect

Cortex

Line bisection and cognitive plasticity of unilateral neglect of space

Brain and Cognition

Consciousness and neuroscience

Cerebral Cortex

Disorders of space exploration and cognition

The breakdown and rehabilitation of visuospatial dysfunction in brain-injured patients

International Rehabilitation Medicine

The behavioural management of neglect

A further study of visual agnosia

Brain

Where in the brain does visual attention select the forest and the trees?

Nature

Qualitative analysis of unilateral spatial neglect in relation to laterality of cerebral lesions

Journal of Neurology, Neurosurgery & Psychiatry

When is a cue not a cue? On the intractability of visuospatial neglect

Neuropsychological Rehabilitation

Homing in on neglect: A case study of visual search

Cortex

When two is one: A case study of spatial parsing in visual neglect

Perception

Spatial neglect: Position papers on theory and practice

Toward a principled explanation of unilateral neglect

Cognitive Neuropsychology

Right sided cueing can ameliorate left neglect

Neuropsychological Rehabilitation

Neglect and related disorders

Neurophysiological and neuropsychological aspects of spatial neglect

Regular Article
Neglect of Awareness☆,☆☆