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American Journal of Ophthalmology Dec 1998To alert ophthalmologists to the use of Ishihara color plates in the detection of simultanagnosia.
PURPOSE
To alert ophthalmologists to the use of Ishihara color plates in the detection of simultanagnosia.
METHODS
We examined seven patients referred for impaired vision. Evaluation included color plate testing with Ishihara color plates.
RESULTS
All seven patients had simultanagnosia, with marked difficulty in identifying the numbers in Ishihara color plates despite adequate visual acuity and the ability to name all of the colors in the plates correctly. One of these patients was referred with the diagnosis of a cone dystrophy because of her poor performance on the Ishihara test. All of the patients had bilateral occipitoparietal damage or atrophy on magnetic resonance imaging.
CONCLUSIONS
Ophthalmologists must be aware that a poor performance with Ishihara plates may not be attributable to an impairment of color vision but rather to occipitoparietal brain damage associated with simultanagnosia.
Topics: Agnosia; Brain Diseases; Color Perception; Color Perception Tests; Humans; Magnetic Resonance Imaging; Occipital Lobe; Parietal Lobe
PubMed: 9860021
DOI: 10.1016/s0002-9394(98)00187-1 -
Current Opinion in Neurology Feb 2011Both monkey and human neuroimaging studies show that visual processing beyond the striate cortex involves a highly complex network of regions with modular functions.... (Review)
Review
PURPOSE OF REVIEW
Both monkey and human neuroimaging studies show that visual processing beyond the striate cortex involves a highly complex network of regions with modular functions. Lesions within this network lead to specific clinical syndromes. In this review we discuss studies on blindsight, which is the ability of remaining regions to support vision in the absence of striate cortex or visual awareness, recent work on 'ventral stream' syndromes such as object agnosia, alexia, prosopagnosia, and topographagnosia, which follow damage to medial occipitotemporal structures, and simultanagnosia, the classic 'dorsal stream' deficit related to bilateral occipitoparietal lesions.
RECENT FINDINGS
We highlight work on the anatomic basis of blindsight, the recent description of the new disorder developmental topographic disorientation, and studies contrasting global and local perception in simultanagnosia.
SUMMARY
These studies advance our understanding of the mechanisms of complex visual processing and provide an important neuropsychological complement to our expanding knowledge about vision from functional neuroimaging.
Topics: Agnosia; Blindness; Cognition Disorders; Dyslexia; Humans; Prosopagnosia; Vision Disorders; Vision, Ocular; Visual Cortex; Visual Pathways; Visual Perception
PubMed: 21102334
DOI: 10.1097/WCO.0b013e328341a5c2 -
Bulletin of the Los Angeles... 1946
Topics: Agnosia; Aphasia; Delusions; Mental Disorders; Paranoid Disorders
PubMed: 20285704
DOI: No ID Found -
Cognitive Neuropsychology Mar 2004We examined object identification in two simultanagnosic patients, ES and GK. We show that the patients tended to identify animate objects more accurately than inanimate...
We examined object identification in two simultanagnosic patients, ES and GK. We show that the patients tended to identify animate objects more accurately than inanimate objects (Experiments 1 and 4). The patients also showed relatively good identification of objects that could be recognised from their global shape, but not objects whose recognition depended on their internal detail (Experiment 2). Indeed, the presence of local segmentation cues disrupted global identification (Experiment 3). Identification was aided, though, by the presence of surface colour and texture (Experiment 4). We suggest that the patients could derive global representations of objects that served to recognise animate items. In contrast, they were impaired at coding parts-based representations for the identification of inanimate objects.
PubMed: 21038214
DOI: 10.1080/02643290342000564 -
Journal of AAPOS : the Official... Oct 2007A 7-year-old boy with a history of low birth weight and perinatal hypoxia presented with symptoms of a spatial disorder of attention (simultanagnosia) and defective foot...
A 7-year-old boy with a history of low birth weight and perinatal hypoxia presented with symptoms of a spatial disorder of attention (simultanagnosia) and defective foot movements under visual control (optic ataxia), similar to a complex known as Balint's syndrome. Imaging revealed mature areas of ischemic damage in the posterior parietal and superior occipital lobes consistent with the diagnosis. Balint's syndrome in children is rarely reported and is important to recognize to allow adequate rehabilitation and environmental adaptation.
Topics: Agnosia; Ataxia; Attention Deficit Disorder with Hyperactivity; Child; Diagnosis, Differential; Humans; Hypoxia, Brain; Magnetic Resonance Imaging; Male; Occipital Lobe; Parietal Lobe; Syndrome; Vision, Low; Visual Perception
PubMed: 17933675
DOI: 10.1016/j.jaapos.2007.03.007 -
Neuropsychologia Aug 2016Simultanagnosia caused by posterior temporo-parietal brain damage is characterized through an inability to recognize a global Gestalt from an arrangement of single...
Simultanagnosia caused by posterior temporo-parietal brain damage is characterized through an inability to recognize a global Gestalt from an arrangement of single objects while perception of single objects appears widely intact. We asked whether recognition of single objects in simultanagnosia is still intact if objects are really large, i.e. if they exceed the size of a usual computer screen. Single objects were presented in three different sizes: 'regular', 'medium', and 'large'. Simultanagnosia patients demonstrated a decrease of recognition performance with increasing object size; recognition of 'large' objects was significantly impaired while perception of 'regular' sized objects was unaffected. The results argue against the traditional view of preserved recognition of single objects in simultanagnosia. They provide evidence for a more general perceptual impairment that emerges irrespective of presenting single or multiple objects, but whenever the visual system has to assemble information over larger spatial distances or other demanding viewing conditions. It appears that perception of large single objects requires intact abilities of dorsal Gestalt processing, in addition to regular functions of ventral object recognition.
Topics: Aged; Agnosia; Cerebral Cortex; Female; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Neuroimaging; Pattern Recognition, Visual; Photic Stimulation; Principal Component Analysis; Psychophysics; Recognition, Psychology; Size Perception; Statistics, Nonparametric
PubMed: 27267104
DOI: 10.1016/j.neuropsychologia.2016.06.002 -
Neuropsychologia Mar 2009The integration of visual elements into global perception seems to be implemented separately to single object perception. This assumption is supported by the existence...
The integration of visual elements into global perception seems to be implemented separately to single object perception. This assumption is supported by the existence of patients with simultanagnosia who can identify single objects but are incapable of integrating multiple visual items. We investigated a case of simultanagnosia due to posterior cortical atrophy without structural brain damage who demonstrated an incomplete simultanagnosia. The patient successfully recognized a global stimulus in one trial but failed to do so just a few seconds later. Using event-related fMRI, we contrasted post hoc selected trials of successful global perception with trials of global recognition failure. We found circumscribed clusters of activity at the right and left primary intermediate sulci and a bilateral cluster at the ventral precuneus. The integration of multiple visual elements resulting in a conscious perception of their gestalt seems to rely on these bilateral structures in the human lateral and medial inferior parietal cortex.
Topics: Agnosia; Brain Mapping; Cerebral Cortex; Chi-Square Distribution; Female; Fluorodeoxyglucose F18; Functional Laterality; Humans; Image Processing, Computer-Assisted; Magnetic Resonance Imaging; Middle Aged; Oxygen; Pattern Recognition, Visual; Photic Stimulation; Positron-Emission Tomography; Psychophysics
PubMed: 19038276
DOI: 10.1016/j.neuropsychologia.2008.10.025 -
Neuropsychologia 2006One major function of parietal cortex is to direct our attention towards salient stimuli. The present data suggest that it also plays an important role in visual gestalt... (Comparative Study)
Comparative Study
One major function of parietal cortex is to direct our attention towards salient stimuli. The present data suggest that it also plays an important role in visual gestalt perception. Patients with simultanagnosia following lesions in this area are not able to extract the meaning of a visual scene whereas being perfectly able to recognise individual objects of this scene. We tested two patients with simultanagnosia with hierarchical Navon figures combined with eye movements recordings. The patients' performance allowed us to compare directly the scan paths in trials in which the global letter shape was recognised with trials in which the global letter shape was not recognised. We did not find any obvious differences in the eye movement pattern related to the two perceptual situations. The two patients did not show a significant problem in shifting their eyes (and thus possibly also their attentional focus) to all aspects of the complex visual stimulus when attempting to bind together the different elements of spatially distributed information. The results demonstrate that restricted ocular exploration cannot be the reason for the patients' inability to recognise the global shape of stimuli. Our data rather suggest a role of parietal cortex in visual gestalt perception that is beyond its role of directing attention towards relevant objects.
Topics: Agnosia; Attention; Brain Mapping; Cerebral Cortex; Electromyography; Eye Movements; Female; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Neuropsychological Tests; Pattern Recognition, Visual; Photic Stimulation; Positron-Emission Tomography; Time Factors
PubMed: 16806318
DOI: 10.1016/j.neuropsychologia.2006.05.012 -
Neuropsychologia May 2010Patients with simultanagnosia following bilateral parieto-temporo-occipital brain damage show a characteristic impairment of global gestalt perception, while their...
Patients with simultanagnosia following bilateral parieto-temporo-occipital brain damage show a characteristic impairment of global gestalt perception, while their perception of individual objects or elements remains intact. For instance, when shown 'hierarchical' stimuli comprising a larger global object (e.g. a large letter) made up from smaller components (e.g. multiple small letters), they typically report seeing one of the smaller components but not the global figure. Recent work on simultanagnosia revealed that global perception can be improved if local element spacing is reduced. However, it is still unclear whether the retinal separation or the physical (post-size-constancy) spatial separation is critical. Here, we presented various hierarchical global/local letter stimuli at different viewing distances and sizes to separate the impacts of retinal versus physical size. Our findings indicate a key role for visual angle in determining simultanagnosic perception. We observed that not only retinal spacing (in terms of visual angle) between local elements had a major impact on global perception in simultanagnosia, but also the physical size of the separation between local elements, provided that binocular cues to viewing distance were available. The results indicate both pre-size-constancy retinal influences and binocular-post-constancy influences upon conscious perception in simultanagnosia.
Topics: Aged; Agnosia; Brain Mapping; Discrimination Learning; Female; Fluorodeoxyglucose F18; Humans; Magnetic Resonance Imaging; Pattern Recognition, Visual; Photic Stimulation; Positron-Emission Tomography; Psychophysics; Retina; Size Perception; Visual Pathways
PubMed: 20170667
DOI: 10.1016/j.neuropsychologia.2010.02.013 -
Rinsho Shinkeigaku = Clinical Neurology 2015A 68-year-old man was admitted to our hospital for rehabilitation of topographical disorientation. Brain magnetic resonance imaging revealed infarction in the right...
A 68-year-old man was admitted to our hospital for rehabilitation of topographical disorientation. Brain magnetic resonance imaging revealed infarction in the right medial side of the occipital lobe. On neuropsychological testing, he scored low for the visual information-processing task; however, his overall cognitive function was retained. He could identify parts of the picture while describing the context picture of the Visual Perception Test for Agnosia but could not explain the contents of the entire picture, representing so-called simultanagnosia. Further, he could morphologically perceive both familiar and new scenes, but could not identify them, representing so-called scene agnosia. We report this case because simultanagnosia associated with a right occipital lobe lesion is rare.
Topics: Aged; Agnosia; Humans; Infarction, Posterior Cerebral Artery; Magnetic Resonance Angiography; Magnetic Resonance Imaging; Male
PubMed: 26369377
DOI: 10.5692/clinicalneurol.cn-000731