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Cortex; a Journal Devoted To the Study... Nov 2022
Topics: Humans; Perceptual Disorders; Functional Laterality
PubMed: 36183572
DOI: 10.1016/j.cortex.2022.09.001 -
Current Neurology and Neuroscience... Sep 2021Historical and contemporary treatments of visual agnosia and neglect regard these disorders as largely unrelated. It is thought that damage to different neural processes... (Review)
Review
PURPOSE OF REVIEW
Historical and contemporary treatments of visual agnosia and neglect regard these disorders as largely unrelated. It is thought that damage to different neural processes leads directly to one or the other condition, yet apperceptive variants of agnosia and object-centered variants of neglect share remarkably similar deficits in the quality of conscious experience. Here we argue for a closer association between "apperceptive" variants of visual agnosia and "object-centered" variants of visual neglect. We introduce a theoretical framework for understanding these conditions based on "scale attention", which refers to selecting boundary and surface information at different levels of the structural hierarchy in the visual array.
RECENT FINDINGS
We review work on visual agnosia, the cortical structures and cortico-cortical pathways that underlie visual perception, visuospatial neglect and object-centered neglect, and attention to scale. We highlight direct and indirect pathways involved in these disorders and in attention to scale. The direct pathway involves the posterior vertical segments of the superior longitudinal fasciculus that are positioned to link the established dorsal and ventral attentional centers in the parietal cortex with structures in the inferior occipitotemporal cortex associated with visual apperceptive agnosia. The connections in the right hemisphere appear to be more important for visual conscious experience, whereas those in the left hemisphere appear to be more strongly associated with the planning and execution of visually guided grasps directed at multi-part objects such as tools. In the latter case, semantic and functional information must drive the selection of the appropriate hand posture and grasp points on the object. This view is supported by studies of grasping in patients with agnosia and in patients with neglect that show that the selection of grasp points when picking up a tool involves both scale attention and semantic contributions from inferotemporal cortex. The indirect pathways, which include the inferior fronto-occipital and horizontal components of the superior longitudinal fasciculi, involve the frontal lobe, working memory and the "multiple demands" network, which can shape the content of visual awareness through the maintenance of goal- and task-based abstractions and their influence on scale attention. Recent studies of human cortico-cortical pathways necessitate revisions to long-standing theoretical views on visual perception, visually guided action and their integrations. We highlight findings from a broad sample of seemingly disparate areas of research to support the proposal that attention to scale is necessary for typical conscious visual experience and for goal-directed actions that depend on functional and semantic information. Furthermore, we suggest that vertical pathways between the parietal and occipitotemporal cortex, along with indirect pathways that involve the premotor and prefrontal cortex, facilitate the operations of scale attention.
Topics: Agnosia; Humans; Perceptual Disorders; Visual Pathways; Visual Perception
PubMed: 34586544
DOI: 10.1007/s11910-021-01139-6 -
JPMA. the Journal of the Pakistan... Apr 2022Hemi-spatial neglect (HSN) is a debilitating post stroke cognitive deficit resulting in reduced attention to stimuli presented in the contra-lateral hemi-visual field....
Hemi-spatial neglect (HSN) is a debilitating post stroke cognitive deficit resulting in reduced attention to stimuli presented in the contra-lateral hemi-visual field. It adversely impacts patient's medical recovery, activities of daily living and quality of life. Early referral to Rehabilitation Medicine specialist for thorough evaluation, prompt recognition of functional impairments and formulation of a comprehensive rehabilitation plan unique to patient is important. It is part of the comprehensive and holistic management of stroke patients with HSN. We summarize the current management strategies used for post-stroke HSN rehabilitation with the options including non-invasive brain stimulation, visuomotor feedback training, robotic rehabilitation and trans-dermal nicotine patch.
Topics: Activities of Daily Living; Humans; Perceptual Disorders; Quality of Life; Stroke; Stroke Rehabilitation
PubMed: 35614624
DOI: 10.47391/JPMA.22-32 -
Clinics in Geriatric Medicine Feb 2020Psychotic and compulsive symptoms in Parkinson disease are highly prevalent and associated with poor outcomes and greater caregiver burden. When acute, delirium should... (Review)
Review
Psychotic and compulsive symptoms in Parkinson disease are highly prevalent and associated with poor outcomes and greater caregiver burden. When acute, delirium should be ruled out or treated accordingly. When chronic, comorbid systemic illnesses, dementia, and psychiatric disorders should be considered. Reduction and discontinuation of anticholinergics, amantadine, dopamine agonists, and levodopa as tolerated, as well as adjunctive clozapine or quetiapine are frequently effective to manage Parkinson disease psychosis. Pimavanserin appears effective but is not widely available, and more experience is needed. Dopamine agonist discontinuation is usually successful for impulse control disorders, but requires frequent monitoring, documentation, and caregiver involvement.
Topics: Aged; Diagnosis, Differential; Disruptive, Impulse Control, and Conduct Disorders; Humans; Parkinson Disease; Patient Care Management; Perceptual Disorders; Psychotic Disorders
PubMed: 31733691
DOI: 10.1016/j.cger.2019.09.004 -
Acta Psychiatrica Scandinavica Oct 2019Subthreshold perceptual abnormalities are commonly used to identify individuals at clinical high risk (CHR) for developing a psychotic disorder. Predictive validity for...
OBJECTIVE
Subthreshold perceptual abnormalities are commonly used to identify individuals at clinical high risk (CHR) for developing a psychotic disorder. Predictive validity for modality-specific perceptual abnormality severity on psychosis risk is unknown.
METHODS
We examined prospectively collected data from 164 individuals age 12-35 meeting criteria for CHR followed for 6-24 months or until conversion to psychosis. Using intake interview notes, baseline perceptual abnormality scores were split into auditory, visual, somatic/tactile, and olfactory/gustatory components, and auditory scores were further split into those for verbal vs non-verbal content. Relationships between perceptual abnormality characteristics and conversion were assessed with Cox proportional hazards regression and logistic regression.
RESULTS
Unusual thought content and paranoia were predictive of conversion, but no modality-specific perceptual abnormality score predicted conversion status or days to conversion. However, when auditory perceptual abnormalities were further categorized as verbal vs non-verbal, the severity of verbal experiences was predictive of conversion to psychosis (P = 0.007).
CONCLUSIONS
Perceptual abnormality scores failed to meaningfully predict conversion to psychosis in either direction in this CHR sample. However, verbal auditory experiences may identify a group of CHR individuals at elevated risk of conversion. Further exploration of the relationship between phenomenological aspects of perceptual abnormalities and conversion risk is warranted.
Topics: Adolescent; Case-Control Studies; Child; Female; Hallucinations; Humans; Male; Paranoid Disorders; Perception; Perceptual Disorders; Predictive Value of Tests; Prodromal Symptoms; Psychotic Disorders; Retrospective Studies; Risk Factors; Severity of Illness Index; Young Adult
PubMed: 31355420
DOI: 10.1111/acps.13078 -
Handbook of Clinical Neurology 2021While there is a long history of rehabilitation for motor deficits following cerebral lesions, less is known about our ability to improve visual deficits. Vision...
While there is a long history of rehabilitation for motor deficits following cerebral lesions, less is known about our ability to improve visual deficits. Vision therapy, prisms, occluders, and filters have been advocated for patients with mild traumatic brain injury, on the premise that some of their symptoms may reflect abnormal visual or ocular motor function, but the evidence for their efficacy is modest. For hemianopia, attempts to restore vision have had unimpressive results, though it appears possible to generate blindsight through training. Strategic approaches that train more efficient use of visual search in hemianopia have shown consistent benefit in visual function, while prism aids may help some patients. There are many varieties of alexia. Strategic adaptation of saccades can improve hemianopic alexia, but there has been less work and mixed results for pure alexia, neglect dyslexia, attentional dyslexia, and the central dyslexias. A number of approaches have been tried in prosopagnosia, with recent studies of small groups suggesting that face perception of prosopagnosic subjects can be enhanced through perceptual learning.
Topics: Adaptation, Physiological; Dyslexia; Hemianopsia; Humans; Perceptual Disorders; Vision Disorders; Visual Perception
PubMed: 33832686
DOI: 10.1016/B978-0-12-821377-3.00015-5 -
Developmental Medicine and Child... Apr 2021To assess the prevalence of elementary visuospatial perception (EVSP) deficit in children with neurodevelopmental disorders.
AIM
To assess the prevalence of elementary visuospatial perception (EVSP) deficit in children with neurodevelopmental disorders.
METHOD
Using a screening test designed and validated to measure dorsal EVSP ability, 168 children (122 males, 46 females; mean age 10y [SD 1y 10mo], range 4y 8mo-16y 4mo) diagnosed with developmental coordination disorder (DCD), specific learning disorder (SLD), attention-deficit/hyperactivity disorder (ADHD), and/or oral language disorder were compared with a group of 184 typically developing children. We also tested 14 children with binocular vision dysfunction and no neurodevelopmental disorder.
RESULTS
Children with SLD scored below the interquartile range of typically developing children as frequently (59%) as children with DCD, but only 5% were severely impaired (i.e. scored as outliers). Children with DCD were the most severely impaired (22% of outliers), even more so when they exhibited a co-occuring disorder. Children with language disorder and those with binocular vision dysfunction scored similarly to the group of typically developing children.
INTERPRETATION
These results confirm the importance of assessing EVSP in the clinical evaluation of children with neurodevelopmental disorders, in particular those presenting with DCD or SLD. What this paper adds More than half of children with developmental coordination disorder (DCD) scored below the normal interquartile range on the elementary visuospatial perception (EVSP) test. More than half of children with specific learning disorder (SLD) scored below the normal interquartile range on the EVSP test. Twenty-two percent of children with DCD performed as outliers on the EVSP test. Children with language disorder and those with binocular vision dysfunction scored similarly to typically developing children.
Topics: Child; Female; Humans; Male; Neurodevelopmental Disorders; Perceptual Disorders; Space Perception; Visual Perception
PubMed: 33314050
DOI: 10.1111/dmcn.14743 -
Revue Neurologique Nov 2021Visuospatial neglect is a frequent and disabling consequence of injuries to the right hemisphere. Patients with neglect show signs of impaired attention for left-sided... (Review)
Review
Visuospatial neglect is a frequent and disabling consequence of injuries to the right hemisphere. Patients with neglect show signs of impaired attention for left-sided events, which depends on dysfunction of fronto-parietal networks. After unilateral injury, such as stroke, these networks and their contralateral homologs can reorganize following multiple potential trajectories, which can be either adaptive or maladaptive. This article presents possible factors influencing the profile of evolution of neglect towards recovery or chronicity, and highlights potential mechanisms that may constrain these processes in time and space. The integrity of white matter pathways within and between the hemisphere appears to pose crucial connectivity constraints for compensatory brain plasticity from remote brain regions. Specifically, the availability of a sufficient degree of inter-hemispheric connectivity might be critical to shift the role of the undamaged left hemisphere in spatial neglect, from exerting maladaptive effects, to promoting compensatory activity.
Topics: Attention; Brain; Brain Mapping; Functional Laterality; Humans; Perceptual Disorders; Space Perception; Stroke; White Matter
PubMed: 34561121
DOI: 10.1016/j.neurol.2021.07.015 -
Neuropsychologia Jun 2022Synesthesia represents an atypical merging of percepts, in which a given sensory experience (e.g., words, letters, music) triggers sensations in a different perceptual...
Synesthesia represents an atypical merging of percepts, in which a given sensory experience (e.g., words, letters, music) triggers sensations in a different perceptual domain (e.g., color). According to recent estimates, the vast majority of the reported cases of synesthesia involve a visual experience. Purely non-visual synesthesia is extremely rare and to date there is no reported case of a congenitally blind synesthete. Moreover, it has been suggested that congenital blindness impairs the emergence of synesthesia-related phenomena such as multisensory integration and cross-modal correspondences between non-visual senses (e.g., sound-touch). Is visual experience necessary to develop synesthesia? Here we describe the case of a congenital blind man (CB) reporting a complex synesthetic experience, involving numbers, letters, months and days of the week. Each item is associated with a precise position in mental space and with a precise tactile texture. In one experiment we empirically verified the presence of number-texture and letter-texture synesthesia in CB, compared to non-synesthete controls, probing the consistency of item-texture associations across time and demonstrating that synesthesia can develop without vision. Our data fill an important void in the current knowledge on synesthesia and shed light on the mechanisms behind sensory crosstalk in the human mind.
Topics: Blindness; Color Perception; Humans; Male; Music; Perceptual Disorders; Synesthesia; Touch; Touch Perception
PubMed: 35358538
DOI: 10.1016/j.neuropsychologia.2022.108226 -
Headache Oct 2021The aim of this narrative review is to explore the relationship between visual snow syndrome (VSS), migraine, and a group of other perceptual disorders. (Review)
Review
OBJECTIVE
The aim of this narrative review is to explore the relationship between visual snow syndrome (VSS), migraine, and a group of other perceptual disorders.
BACKGROUND
VSS is characterized by visual snow and additional visual and nonvisual disturbances. The clinical picture suggests a hypersensitivity to internal and external stimuli. Imaging and electrophysiological findings indicate a hyperexcitability of the primary and secondary visual areas of the brain possibly due to an impairment of inhibitory feedback mechanisms. Migraine is the most frequent comorbidity. Epidemiological and clinical studies indicate that other perceptual disorders, such as tinnitus, fibromyalgia, and dizziness, are associated with VSS. Clinical overlaps and parallels in pathophysiology might exist in relation to migraine.
METHODS
We performed a PubMed and Google Scholar search with the following terms: visual snow syndrome, entoptic phenomenon, fibromyalgia, tinnitus, migraine, dizziness, persistent postural-perceptual dizziness (PPPD), comorbidities, symptoms, pathophysiology, thalamus, thalamocortical dysrhythmia, and salience network.
RESULTS
VSS, fibromyalgia, tinnitus, and PPPD share evidence of a central disturbance in the processing of different stimuli (visual, somatosensory/pain, acoustic, and vestibular) that might lead to hypersensitivity. Imaging and electrophysiological findings hint toward network disorders involving the sensory networks and other large-scale networks involved in the management of attention and emotional processing. There are clinical and epidemiological overlaps between these disorders. Similarly, migraine exhibits a multisensory hypersensitivity even in the interictal state with fluctuation during the migraine cycle. All the described perceptual disorders are associated with migraine suggesting that having migraine, that is, a disorder of sensory processing, is a common link.
CONCLUSION
VSS, PPPD, fibromyalgia, and chronic tinnitus might lie on a spectrum of perceptual disorders with similar pathophysiological mechanisms and the common risk factor migraine. Understanding the underlying network disturbances might give insights into how to improve these currently very difficult to treat conditions.
Topics: Comorbidity; Dizziness; Fibromyalgia; Humans; Migraine Disorders; Perceptual Disorders; Tinnitus; Vision Disorders
PubMed: 34570907
DOI: 10.1111/head.14213