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Brain : a Journal of Neurology Oct 2021
Review
Topics: Agnosia; Humans; Imagination; Pattern Recognition, Visual; Visual Cortex; Visual Perception
PubMed: 33856025
DOI: 10.1093/brain/awab159 -
Current Neurology and Neuroscience... Nov 2003The visual agnosias are an intriguing class of clinical phenomena that have important implications for current theories of high-level vision. Visual agnosia is defined... (Review)
Review
The visual agnosias are an intriguing class of clinical phenomena that have important implications for current theories of high-level vision. Visual agnosia is defined as impaired object recognition that cannot be attributed to visual loss, language impairment, or a general mental decline. At least in some instances, agnostic patients generate an adequate internal representation of the stimulus but fail to recognize it. In this review, we begin by describing the classic works related to the visual agnosias, followed by a description of the major clinical variants and their occurrence in degenerative disorders. In keeping with the theme of this issue, we then discuss recent contributions to this domain. Finally, we present evidence from functional imaging studies to support the clinical distinction between the various types of visual agnosias.
Topics: Agnosia; Humans; Neurodegenerative Diseases; Prosopagnosia
PubMed: 14565906
DOI: 10.1007/s11910-003-0055-4 -
Revue Neurologique 2017Visual agnosia encompasses all disorders of visual recognition within a selective visual modality not due to an impairment of elementary visual processing or other... (Review)
Review
Visual agnosia encompasses all disorders of visual recognition within a selective visual modality not due to an impairment of elementary visual processing or other cognitive deficit. Based on a sequential dichotomy between the perceptual and memory systems, two different categories of visual object agnosia are usually considered: 'apperceptive agnosia' and 'associative agnosia'. Impaired visual recognition within a single category of stimuli is also reported in: (i) visual object agnosia of the ventral pathway, such as prosopagnosia (for faces), pure alexia (for words), or topographagnosia (for landmarks); (ii) visual spatial agnosia of the dorsal pathway, such as cerebral akinetopsia (for movement), or orientation agnosia (for the placement of objects in space). Focal brain injuries provide a unique opportunity to better understand regional brain function, particularly with the use of effective statistical approaches such as voxel-based lesion-symptom mapping (VLSM). The aim of the present work was twofold: (i) to review the various agnosia categories according to the traditional visual dual-pathway model; and (ii) to better assess the anatomical network underlying visual recognition through lesion-mapping studies correlating neuroanatomical and clinical outcomes.
Topics: Agnosia; Brain Injuries; Brain Mapping; Cognition Disorders; Humans; Nerve Net; Neuroimaging; Neuropsychological Tests; Visual Pathways; Visual Perception
PubMed: 28843416
DOI: 10.1016/j.neurol.2017.07.009 -
Neurologic Clinics May 2003As was originally proposed by Lissauer, visual recognition may break down either at an apperceptive or at an associative level. At an apperceptive level, finer grain... (Review)
Review
As was originally proposed by Lissauer, visual recognition may break down either at an apperceptive or at an associative level. At an apperceptive level, finer grain distinctions may be made; the authors distinguished here between disorders of shape recognition and perceptual integration. It is not the case, however, that all patients with visual recognition deficits have impaired perception: poor recognition and naming may also result from damage to stored perceptual knowledge (e.g., structural descriptions), from problems in accessing semantic knowledge, from perceptual knowledge, or from impairments to semantic knowledge itself. These represent different types of associative deficit. In some cases, mild damage to stored perceptual knowledge also generates problems that are more severe on naming than on recognition and more severe for some categories of objects than others.
Topics: Adult; Agnosia; Form Perception; Humans; Magnetic Resonance Imaging; Male; Occipital Lobe; Sinus Thrombosis, Intracranial; Temporal Lobe
PubMed: 12916489
DOI: 10.1016/s0733-8619(02)00095-6 -
Brain and Nerve = Shinkei Kenkyu No... Oct 2011Progressive visual agnosia was discovered in the 20th century following the discovery of classical non-progressive visual agnosia. In contrast to the classical type,... (Review)
Review
Progressive visual agnosia was discovered in the 20th century following the discovery of classical non-progressive visual agnosia. In contrast to the classical type, which is caused by cerebral vascular disease or traumatic injury, progressive visual agnosia is a symptom of neurological degeneration. The condition of progressive visual loss, including visual agnosia, and posterior cerebral atrophy was named posterior cortical atrophy (PCA) by Benson et al. (1988). Progressive visual agnosia is also observed in semantic dementia (SD) and other degenerative diseases, but there is a difference in the subtype of visual agnosia associated with these diseases. Lissauer (1890) classified visual agnosia into apperceptive and associative types, and it in most cases, PCA is associated with the apperceptive type. However, SD patients exhibit symptoms of associative visual agnosia before changing to those of semantic memory disorder. Insights into progressive visual agnosia have helped us understand the visual system and discover how we "perceive" the outer world neuronally, with regard to consciousness. Although PCA is a type of atypical dementia, its diagnosis is important to enable patients to live better lives with appropriate functional support.
Topics: Agnosia; Disease Progression; Humans
PubMed: 21987565
DOI: No ID Found -
Transactions of the Ophthalmological... 1972
Review
Topics: Agnosia; Blindness; Dyslexia; Female; Humans; Memory; Visual Perception
PubMed: 4577659
DOI: No ID Found -
Neuropsychological Rehabilitation Dec 2019Visual agnosia and Balint's syndrome are complex neurological disorders of the higher visual system that can have a remarkable impact on individuals' lives.... (Review)
Review
Visual agnosia and Balint's syndrome are complex neurological disorders of the higher visual system that can have a remarkable impact on individuals' lives. Rehabilitation of these individuals is important to enable participation in everyday activities despite the impairment. However, the literature about the rehabilitation of these disorders is virtually silent. Therefore, the aim of this systematic review is to give an overview of available literature describing treatment approaches and their effectiveness with regard to these disorders. The search engines Psychinfo, Amed, and Medline were used, resulting in 22 articles meeting the criteria for inclusion. Only articles describing acquired disorders were considered. These articles revealed that there is some information available on the major subtypes of visual agnosia as well as on Balint's syndrome which practising clinicians can consult for guidance. With regard to the type of rehabilitation, compensatory strategies have proven to be beneficial in most of the cases. Restorative training on the other hand has produced mixed results. Concluding, although still scarce, a scientific foundation about the rehabilitation of visual agnosia and Balint's syndrome is evolving. The available approaches give valuable information that can be built upon in the future.
Topics: Agnosia; Humans; Prosopagnosia; Treatment Outcome; Vision Disorders; Visual Perception
PubMed: 29366371
DOI: 10.1080/09602011.2017.1422272 -
Handbook of Clinical Neurology 2021The term visual agnosia is used to refer to recognition disorders that are confined to the visual modality, that are not due to an impairment in sensory functions, and...
The term visual agnosia is used to refer to recognition disorders that are confined to the visual modality, that are not due to an impairment in sensory functions, and that cannot be explained by other cognitive deficits or by general reduction in intellectual ability. Here, we describe the different types of visual agnosia that have been reported (form agnosia, integrative agnosia, associative agnosia, transformational and orientation agnosia as well as category-specific impairments such as pure alexia and prosopagnosia) and how they relate to the current understanding of visual object recognition. Together with related disorders such as simultanagnosia, texture agnosia, aphantasia, and optic aphasia, these visual perceptual impairments can have severe consequences for those affected. We suggest how in-depth assessment can be carried out to determine the type and the extent of these impairments. In the context of clinical assessment, a step-by-step approach reflecting a posterior to anterior gradient in visual object recognition, from more perceptual to more memory-related processes, is suggested. Individually tailored interventions targeting the identified impairments can be initiated based on the results of the assessment.
Topics: Agnosia; Cognition Disorders; Humans; Neuropsychological Tests; Orientation; Visual Perception
PubMed: 33832675
DOI: 10.1016/B978-0-12-821377-3.00008-8 -
BMJ (Clinical Research Ed.) Nov 2012
Topics: Agnosia; Humans
PubMed: 23144207
DOI: 10.1136/bmj.e7342 -
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