The syndrome of unilateral spatial neglect is one of the most disabling neuropsychological deficits caused by brain damage, most frequently in the right cerebral hemisphere. Neglect affects over 60% of right-brain-damaged patients, particularly in the acute phase after stroke. The manifestations of neglect are manifold, and may occur independent of each other, but all of them share a divide, which distinguishes the neglected (namely, not explored, where events are undetected) from the non-neglected side of space. Clinical manifestations include not only “deficits” (such as impaired search and report of events), but also gratuitous (not required by the environmental set) productions, as perseveration behaviour of varying complexity. Different sectors of space may be selectively affected: one main distinction concerns extra-personal vs. personal, bodily space. Patients may neglect the side of the body contralateral to the lesion, hence, after right-brain damage, the left side. Neglect for the left side of the body includes simple “defective” impairments (personal hemi-neglect, hemi-asomatognosia), and more “complex” productive delusional beliefs (somatoparaphrenia) concerning left body parts (most frequently, though not exclusively, the left hand). These delusions may be variably florid, ranging from the mere disownership of the left hand, to the misattribution of its ownership to another person, with a variety of arguments. These patients may be also unaware of left-sided sensori-motor deficits (anosognosia for hemiplegia, hemianesthesia, hemianopia), and this unawareness may occur independent of hemi-asomatognosia and somatoparaphrenia. Notwithstanding the prima facie higher-level (cognitive) features of these disorders of body knowledge, the relevant neuro-functional representation of the body is mostly, though not exclusively, based on the continuous integration and updating of multisensory signals, as revealed by the effects of direction-specific sensory stimulations (e.g., vestibular caloric) on these bodily manifestations of the neglect syndrome. Also, conditions, in which a conflict between senses (i.e., somatic sensation and vision, as in the Rubber Hand Illusion) is artificially created, may modulate the disownership symptom of somatoparaphrenia in brain-damaged patients, as well as shedding light into the neurofunctional mechanisms supporting the sense of ownership of body parts, and, more generally, of the bodily self, in unimpaired individuals. The view that putatively lower-level processes, as multisensory integration, play a most important role in different aspects of the representation of the body, and of its parts, is in line with the increasing evidence that some basic homeostatic variables are modulated by cerebral cortical activity, and by sensorimotor information known to affect spatial and bodily representations.
Vallar, G. (2015). Spatial neglect. Intervento presentato a: BNPA The British Neuropsychiatry Association 28th AGM - Joint meeting with the British Psychological Society’s Division of Neuropsychology, the UK Functional Symptoms Research Group & in collaboration with the Association of British Neurologists Cognitive Special Interest Group 4, 5 and 6 February 2015, The Royal College of Surgeons, Lincoln’s Inn Fields, London, UK [10.1136/jnnp-2015-311750.12].
Spatial neglect
VALLAR, GIUSEPPE
Primo
2015
Abstract
The syndrome of unilateral spatial neglect is one of the most disabling neuropsychological deficits caused by brain damage, most frequently in the right cerebral hemisphere. Neglect affects over 60% of right-brain-damaged patients, particularly in the acute phase after stroke. The manifestations of neglect are manifold, and may occur independent of each other, but all of them share a divide, which distinguishes the neglected (namely, not explored, where events are undetected) from the non-neglected side of space. Clinical manifestations include not only “deficits” (such as impaired search and report of events), but also gratuitous (not required by the environmental set) productions, as perseveration behaviour of varying complexity. Different sectors of space may be selectively affected: one main distinction concerns extra-personal vs. personal, bodily space. Patients may neglect the side of the body contralateral to the lesion, hence, after right-brain damage, the left side. Neglect for the left side of the body includes simple “defective” impairments (personal hemi-neglect, hemi-asomatognosia), and more “complex” productive delusional beliefs (somatoparaphrenia) concerning left body parts (most frequently, though not exclusively, the left hand). These delusions may be variably florid, ranging from the mere disownership of the left hand, to the misattribution of its ownership to another person, with a variety of arguments. These patients may be also unaware of left-sided sensori-motor deficits (anosognosia for hemiplegia, hemianesthesia, hemianopia), and this unawareness may occur independent of hemi-asomatognosia and somatoparaphrenia. Notwithstanding the prima facie higher-level (cognitive) features of these disorders of body knowledge, the relevant neuro-functional representation of the body is mostly, though not exclusively, based on the continuous integration and updating of multisensory signals, as revealed by the effects of direction-specific sensory stimulations (e.g., vestibular caloric) on these bodily manifestations of the neglect syndrome. Also, conditions, in which a conflict between senses (i.e., somatic sensation and vision, as in the Rubber Hand Illusion) is artificially created, may modulate the disownership symptom of somatoparaphrenia in brain-damaged patients, as well as shedding light into the neurofunctional mechanisms supporting the sense of ownership of body parts, and, more generally, of the bodily self, in unimpaired individuals. The view that putatively lower-level processes, as multisensory integration, play a most important role in different aspects of the representation of the body, and of its parts, is in line with the increasing evidence that some basic homeostatic variables are modulated by cerebral cortical activity, and by sensorimotor information known to affect spatial and bodily representations.
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