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Journal of Cognitive Neuroscience Jan 2008Abstract Information regarding object identity ("what") and spatial location ("where/how to") is largely segregated in visual processing. Under most circumstances,...
Abstract Information regarding object identity ("what") and spatial location ("where/how to") is largely segregated in visual processing. Under most circumstances, however, object identity and location are linked. We report data from a simultanagnosic patient (K.E.) with bilateral posterior parietal infarcts who was unable to "see" more than one object in an array despite relatively preserved object processing and normal preattentive processing. K.E. also demonstrated a finding that has not, to our knowledge, been reported: He was unable to report more than one attribute of a single object. For example, he was unable to name the color of the ink in which words were written despite naming the word correctly. Several experiments demonstrated, however, that perceptual attributes that he was unable to report influenced his performance. We suggest that binding of object identity and location is a limited-capacity operation that is essential for conscious awareness for which the posterior parietal lobe is crucial.
Topics: Acoustic Stimulation; Agnosia; Auditory Perception; Cerebral Infarction; Color Perception; Form Perception; Functional Laterality; Humans; Male; Middle Aged; Neuropsychological Tests; Parietal Lobe; Pattern Recognition, Visual; Photic Stimulation; Recognition, Psychology; Space Perception; Visual Perception
PubMed: 17919075
DOI: 10.1162/jocn.2008.20002 -
Journal of Cognitive Neuroscience Dec 2014Patients suffering from simultanagnosia cannot perceive more than one object at a time. The underlying mechanism is incompletely understood. One hypothesis is that...
Patients suffering from simultanagnosia cannot perceive more than one object at a time. The underlying mechanism is incompletely understood. One hypothesis is that simultanagnosia reflects "tunnel vision," a constricted attention window around gaze, which precludes the grouping of individual objects. Although this idea has a long history in neuropsychology, the question whether the patients indeed have an abnormal attention gradient around the gaze has so far not been addressed. Here we tested this hypothesis in two simultanagnosia patients with bilateral parieto-occipital lesions and two control groups, with and without brain damage. We assessed the participants' ability to discriminate letters presented briefly at fixation with and without a peripheral distractor or in the visual periphery, with or without a foveal distractor. A constricted span of attention around gaze would predict an increased susceptibility to foveated versus peripheral distractors. Contrary to this prediction and unlike both control groups, the patients' ability to discriminate the target decreased more in the presence of peripheral compared with foveated distractors. Thus, the attentional spotlight in simultanagnosia does not fall on foveated objects as previously assumed, but rather abnormally highlights the periphery. Furthermore, we found the same center-periphery gradient in the patients' ability to recognize multiple objects. They detected multiple, but not single objects more accurately in the periphery than at fixation. These results suggest that an abnormal allocation of attention around the gaze can disrupt the grouping of individual objects into an integrated visual scene.
Topics: Aged; Analysis of Variance; Attention Deficit Disorder with Hyperactivity; Brain Injuries; Brain Mapping; Female; Functional Laterality; Humans; Male; Middle Aged; Neuropsychological Tests; Photic Stimulation; Recognition, Psychology; Space Perception; Visual Fields
PubMed: 24893736
DOI: 10.1162/jocn_a_00666 -
Cognitive Neuropsychiatry Jan 2018Bálint's syndrome involves bilateral damage to the parieto-occipital area. The extent of the effect of unilateral damage on the Bálint's triad (oculomotor apraxia,...
INTRODUCTION
Bálint's syndrome involves bilateral damage to the parieto-occipital area. The extent of the effect of unilateral damage on the Bálint's triad (oculomotor apraxia, optic ataxia, and simultanagnosia) remains unknown.
METHODS
We examined a 63-year-old, right-handed woman who developed right hemianopia, oculomotor apraxia, optic ataxia, simultanagnosia, and hemispatial neglect (HSN) for the right after a cerebral infarction, with detailed neuropsychological tests, magnetic resonance imaging, and single photon emission computed tomography (SPECT).
RESULTS
Neuropsychological examination showed that oculomotor apraxia, optic ataxia, and simultanagnosia were more pronounced in the right hemi-space, probably due to the limited eye movement in the right visual field, whereas HSN was restricted to the right hemi-space. Diffusion-weighted MR images revealed hyperintensity in the left parieto-temporo-occipital region, and several spotty areas of the bilateral frontal and parietal subcortical regions. SPECT revealed hypoperfusion in the left parieto-occipital region and frontal operculum and small areas of the right superior parietal lobule.
CONCLUSIONS
The case suggests that asymmetric (more pronounced in the right hemi-space) oculomotor apraxia, optic ataxia, and simultanagnosia occur in an extensive lesion of the left parieto-occipital cortices. Although HSN is not a prerequisite for simultanagnosia, the coexistence of HSN aggravates simultanagnosia in the hemi-space opposite the lesion.
Topics: Agnosia; Apraxias; Ataxia; Cogan Syndrome; Fatal Outcome; Female; Humans; Magnetic Resonance Imaging; Middle Aged; Neuropsychological Tests; Occipital Lobe; Parietal Lobe; Perceptual Disorders
PubMed: 29199507
DOI: 10.1080/13546805.2017.1407304 -
Journal of Neuro-ophthalmology : the... Sep 2018There are many disorders of higher visual processing that result from damage to specific areas of the cerebral cortex that have a specific role in processing certain... (Review)
Review
BACKGROUND
There are many disorders of higher visual processing that result from damage to specific areas of the cerebral cortex that have a specific role in processing certain aspects (modalities) of vision. These can be grouped into those that affect the ventral, or "what?", pathway (e.g., object agnosia, cerebral achromatopsia, prosopagnosia, topographagnosia, and pure alexia), and those that affect the dorsal, or "where?", pathway (e.g., akinetopsia, simultanagnosia, and optic ataxia).
EVIDENCE ACQUISITION
This article reviews pertinent literature, concentrating on recent developments in basic science research and studies of individual patients.
RESULTS
An overview of the current understanding of higher cerebral visual processing is followed by a discussion of the various disorders listed above.
CONCLUSIONS
There has been considerable progress in the understanding of how the extrastriate visual cortex is organized, specifically in relation to functionally specialized visual areas. This permits a better understanding of the individual visual agnosias resulting from damage to these areas.
Topics: Agnosia; Humans; Visual Cortex; Visual Perception
PubMed: 28945627
DOI: 10.1097/WNO.0000000000000556 -
Experimental Brain Research Aug 2010Patients with parieto-occipital brain damage may show simultanagnosia, a selective impairment in the simultaneous perception and integration of multiple objects (global...
Patients with parieto-occipital brain damage may show simultanagnosia, a selective impairment in the simultaneous perception and integration of multiple objects (global perception) with normal recognition of individual objects. Recent findings in patients with simultanagnosia indicate improved global perception at smaller spatial distances between local elements of hierarchical organized complex visual arrays. Global perception thus does not appear to be an all-or-nothing phenomenon but can be modified by the spatial relationship between local elements. The present study aimed to define characteristics of a general principle that accounts for improved global perception of hierarchically organized complex visual arrays in patients with simultanagnosia with respect to the spatial properties of local elements. In detail, we investigated the role of the number and size of the local elements as well as their relationship with each other for the global perception. The findings indicate that global perception increases independently of the size of the global object and depends on the spatial relationship between the local elements and the global object. The results further argue against the possibility of a restriction in the attended or perceived area in simultanagnosia, in the sense that the integration of local elements into a global scene is impaired if a certain spatial "field of view" is exceeded. A possible explanation for these observations might be a shift from global to local saliency in simultanagnosia.
Topics: Aged; Agnosia; Attention; Brain Damage, Chronic; Brain Mapping; Case-Control Studies; Female; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Parietal Lobe; Pattern Recognition, Visual; Photic Stimulation; Reading; Space Perception; Visual Cortex; Visual Pathways
PubMed: 20593278
DOI: 10.1007/s00221-010-2328-x -
Applied Neuropsychology. Adult 2022There is broad consensus on the utility of complex pictures in the assessment of simultanagnosia in patients with acquired brain injury (ABI). To overcome various...
There is broad consensus on the utility of complex pictures in the assessment of simultanagnosia in patients with acquired brain injury (ABI). To overcome various shortcomings of current instruments, we have developed the Birthday Party Test (BPT); a picture description test that contains a neutral scene, a balanced representation of events, and provides clear instructions and a scoring-aid. We have applied the BPT in a large group of patients with ABI ( = 502) and in an age-matched healthy control group ( = 194). Our results show that performance on the BPT was associated with a range of descriptive, neuropsychological and clinical characteristics and that poor test performance appeared to be more common in patients with etiologies that have an increased risk of bilateral damage. Furthermore, we assume a high correspondence between test performance on the BPT and the assessor's clinical judgment of likely having simultanagnosia in preliminary analyses. This study shows the potential usefulness of the BPT to support diagnostic decision making in simultanagnosia. The BPT is made freely available to facilitate its broad application in the clinical assessment of patients with visual impairment and to enable a further evaluation of its utility and validity in future studies.
Topics: Brain Injuries; Humans
PubMed: 32476466
DOI: 10.1080/23279095.2020.1763998 -
Handbook of Clinical Neurology 2018In 1909 Rezsö Bálint published an extraordinary case study of a man with complex visuospatial deficits resulting from bilateral parietal lesions. Despite some...
In 1909 Rezsö Bálint published an extraordinary case study of a man with complex visuospatial deficits resulting from bilateral parietal lesions. Despite some controversies over the nature of reported symptoms, in 1954 Hecaen and Ajuriaguerra conceived the term "Bálint syndrome," not only to honor Bálint's influential work but to firmly conceptualize this striking neurologic disorder. Nowadays it is largely agreed that, while Bálint syndrome may result from multiple etiologies, it is principally diagnosed based on the presence of three symptoms: simultanagnosia, optic ataxia, and ocular apraxia. One of the most striking characteristics of Bálint syndrome, perfectly capturing the nature of this remarkable disorder, is that affected patients cannot perceive more than one object at a time or comprehend multiobject visual scenes due to a lack of ability to detect several objects concurrently and to grasp the spatial relationships between them. This chapter gives an overview of the cognitive mechanisms and neuroanatomy underlying Bálint syndrome, which provides key insights into our understanding of the role of parietal cortex in human attention, visual perception, and visuomotor control. This chapter also pays homage to Glyn Humphreys (1954-2016), who pioneered contributions to the knowledge about complexity of visual and spatial deficits associated with Bálint syndrome.
Topics: History, 20th Century; History, 21st Century; Humans; Perceptual Disorders; Vision Disorders
PubMed: 29519461
DOI: 10.1016/B978-0-444-63622-5.00012-7 -
Cortex; a Journal Devoted To the Study... Jul 2006When presented with two objects patients with simultanagnosia show a marked impairment at naming both items. This has led many authors to conclude that the second item...
When presented with two objects patients with simultanagnosia show a marked impairment at naming both items. This has led many authors to conclude that the second item is not being processed (e.g., Robinson, 2003). However, this deficit may instead reflect a deficit with explicit, or conscious report. We investigated this issue using a semantic priming paradigm that allowed us to assess implicit processing of the second "unseen" item. We presented a patient, with bilateral parietal damage, with pairs of pictures that were either from the same or a different semantic category. The patient was asked to either classify one of the pictures or to name both pictures. When the items were from different categories the patient's classification performance was significantly poorer than when they were from the same category, even though he could rarely explicitly report both items. These findings are consistent with the notion that the meaning of the "unseen" item influenced the reporting of the "seen" item. Consequently, the deficit seen in this patient does not seem to reflect an inability to process more than one item simultaneously but rather a deficit in explicitly identifying multiple items.
Topics: Aged; Awareness; Cerebral Hemorrhage; Data Interpretation, Statistical; Humans; Magnetic Resonance Imaging; Male; Perceptual Disorders; Photic Stimulation; Psychomotor Performance; Reaction Time; Semantics; Syndrome; Visual Perception
PubMed: 16909634
DOI: 10.1016/s0010-9452(08)70412-x -
Revista Clinica Espanola Mar 2016Visual agnosia is defined as an impairment of object recognition, in the absence of visual acuity or cognitive dysfunction that would explain this impairment. This...
Visual agnosia is defined as an impairment of object recognition, in the absence of visual acuity or cognitive dysfunction that would explain this impairment. This condition is caused by lesions in the visual association cortex, sparing primary visual cortex. There are 2 main pathways that process visual information: the ventral stream, tasked with object recognition, and the dorsal stream, in charge of locating objects in space. Visual agnosia can therefore be divided into 2 major groups depending on which of the two streams is damaged. The aim of this article is to conduct a narrative review of the various visual agnosia syndromes, including recent developments in a number of these syndromes.
PubMed: 26358494
DOI: 10.1016/j.rce.2015.07.009 -
Brain Research Jan 2011Simultanagnosia is a disorder of visual attention, defined as an inability to see more than one object at once. It has been conceived as being due to a constriction of...
Simultanagnosia is a disorder of visual attention, defined as an inability to see more than one object at once. It has been conceived as being due to a constriction of the visual "window" of attention, a metaphor that we examine in the present article. A simultanagnosic patient (SL) and two non-simultanagnosic control patients (KC and ES) described social scenes while their eye movements were monitored. These data were compared to a group of healthy subjects who described the same scenes under the same conditions as the patients, or through an aperture that restricted their vision to a small portion of the scene. Experiment 1 demonstrated that SL showed unusually low proportions of fixations to the eyes in social scenes, which contrasted with all other participants who demonstrated the standard preferential bias toward eyes. Experiments 2 and 3 revealed that when healthy participants viewed scenes through a window that was contingent on where they looked (Experiment 2) or where they moved a computer mouse (Experiment 3), their behavior closely mirrored that of patient SL. These findings suggest that a constricted window of visual processing has important consequences for how simultanagnosic patients explore their world. Our paradigm's capacity to mimic simultanagnosic behaviors while viewing complex scenes implies that it may be a valid way of modeling simultanagnosia in healthy individuals, providing a useful tool for future research. More broadly, our results support the thesis that people fixate the eyes in social scenes because they are informative to the meaning of the scene.
Topics: Adolescent; Adult; Agnosia; Analysis of Variance; Attention; Case-Control Studies; Female; Fixation, Ocular; Humans; Male; Middle Aged; Neuropsychological Tests; Perceptual Disorders; Photic Stimulation; Social Perception; Visual Perception; Young Adult
PubMed: 20950591
DOI: 10.1016/j.brainres.2010.10.022