-
Cognitive Neuropsychology 2017Simultanagnosic patients have difficulty in perceiving multiple objects when presented simultaneously. In this review article, I discuss how neuropsychological research... (Review)
Review
Simultanagnosic patients have difficulty in perceiving multiple objects when presented simultaneously. In this review article, I discuss how neuropsychological research on simultanagnosia has been inspirational for two interconnected lines of research related to the core mechanisms by which the visual system processes cluttered scenes. First, I review previous studies on enumeration tasks indicating that, despite their inability to identify multiple objects, simultanagnosic patients can enumerate up to 2-3 elements as efficiently as healthy individuals (the so-called "subitizing" phenomenon). This intriguing observation is one of the first results to support the existence of an "object individuation" mechanism that can spatially tag a limited set of objects simultaneously, and resonates with recent research on the brain dynamics of enumeration in healthy individuals. Second, I further develop the implications of the dissociation between object identification and object enumeration in simultanagnosia specifically for the distinction between object identification and individuation. The latter distinction has been the subject of recent neuroimaging research that has provided fine-grained information on the spatial as well as temporal aspects of object individuation and recognition. The lessons learned from neuropsychological research on exact enumeration in simultanagnosia can be generalized to the normal functioning of the human mind, and have provided insightful clues for cognitive neuroscience.
Topics: Agnosia; Brain; Female; Humans; Individuation; Male; Pattern Recognition, Visual
PubMed: 28632043
DOI: 10.1080/02643294.2017.1331212 -
European Neurology 2011
Topics: Aged; Agnosia; Diffusion Magnetic Resonance Imaging; Humans; Male; Occipital Lobe; Visual Perception
PubMed: 21646784
DOI: 10.1159/000328022 -
Proceedings (Baylor University. Medical... Jan 2020Simultanagnosia is a well-known neurologic symptom characterized by the inability to conceptualize the whole picture despite being able to see individual elements within...
Simultanagnosia is a well-known neurologic symptom characterized by the inability to conceptualize the whole picture despite being able to see individual elements within a visual scene. The pathophysiology involves a lesion to the bilateral parieto-occipital lobe. We report two unusual cases of simultanagnosia and juxtaposed homonymous visual field loss involving aqueductal stenosis-related obstructive hydrocephalus and cardiac arrest due to Brugada syndrome. Clinicians should be aware that simultanagnosia can be the presenting symptom of neuro-ophthalmic disease.
PubMed: 32063790
DOI: 10.1080/08998280.2019.1656013 -
Mayo Clinic Proceedings Oct 1993In a study of 10 patients with degenerative brain disease that manifested as simultanagnosia, our aims were (1) to elucidate their clinical, neuropsychologic, and... (Review)
Review
In a study of 10 patients with degenerative brain disease that manifested as simultanagnosia, our aims were (1) to elucidate their clinical, neuropsychologic, and radiologic findings to determine whether these patients might represent a group distinguishable from those with typical Alzheimer's disease and (2) to help clinicians recognize this entity. All patients were initially examined by ophthalmologists because of visual difficulties, and the simultanagnosia remained undiagnosed until nonophthalmologic complaints developed. Optic ataxia developed in six patients, and all patients had mildly impaired eye movements. All 10 patients could identify colors appropriately. Nine patients had language deficits (anomia, decreased auditory comprehension, alexia, and agraphia) but were fluent and had relative preservation of sentence repetition, and four performed in the normal range on a test of associative fluency. Two patients scored in the normal range on memory tests, all had preserved insight, and nine had no family history of degenerative dementia. The mean age at onset of the disorder was 60 years (range, 50 to 69). Neuroimaging disclosed prominent bilateral occipitoparietal atrophy in nine patients and generalized atrophy in one. With this unusual but consistent clinical, neuropsychologic, and anatomic profile, these patients are clinically distinguishable from those with typical Alzheimer's disease, but until a specific cause has been found, we cannot be certain that they constitute a specific biologic entity. Clinicians should consider this diagnosis in relatively young patients who have slowly progressive nonocular visual complaints.
Topics: Aged; Dementia; Female; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Nystagmus, Pathologic; Occipital Lobe; Parietal Lobe; Temporal Lobe; Tomography, X-Ray Computed; Vision Tests; Visual Acuity; Visual Fields; Visual Perception
PubMed: 8412361
DOI: 10.1016/s0025-6196(12)62267-8 -
Neuropsychologia May 2017Simultanagnosia is a neuropsychological deficit of higher visual processes caused by temporo-parietal brain damage. It is characterized by a specific failure of...
Simultanagnosia is a neuropsychological deficit of higher visual processes caused by temporo-parietal brain damage. It is characterized by a specific failure of recognition of a global visual Gestalt, like a visual scene or complex objects, consisting of local elements. In this study we investigated to what extend this deficit should be understood as a deficit related to specifically the visual domain or whether it should be seen as defective Gestalt processing per se. To examine if simultanagnosia occurs across sensory domains, we designed several auditory experiments sharing typical characteristics of visual tasks that are known to be particularly demanding for patients suffering from simultanagnosia. We also included control tasks for auditory working memory deficits and for auditory extinction. We tested four simultanagnosia patients who suffered from severe symptoms in the visual domain. Two of them indeed showed significant impairments in recognition of simultaneously presented sounds. However, the same two patients also suffered from severe auditory working memory deficits and from symptoms comparable to auditory extinction, both sufficiently explaining the impairments in simultaneous auditory perception. We thus conclude that deficits in auditory Gestalt perception do not appear to be characteristic for simultanagnosia and that the human brain obviously uses independent mechanisms for visual and for auditory Gestalt perception.
Topics: Agnosia; Atrophy; Auditory Perception; Female; Hearing Tests; Humans; Male; Memory, Short-Term; Middle Aged; Neuropsychological Tests; Parietal Lobe; Pattern Recognition, Physiological; Temporal Lobe; Visual Perception
PubMed: 28343958
DOI: 10.1016/j.neuropsychologia.2017.03.026 -
Neurocase Jun 2016We investigated the nature of covertly processed visual elements in a patient with simultanagnosia, a disorder characterized by the inability to perceive multiple...
We investigated the nature of covertly processed visual elements in a patient with simultanagnosia, a disorder characterized by the inability to perceive multiple aspects of a visual scene all at once. Using the first letter of the color words red, green, or blue, we created a novel testing paradigm that combined Navon global-local stimuli with a single-letter Stroop task. The letters R, G, or B were arranged in the overall configuration of a large R, G, or B. The patient never could report seeing the larger letter, and always could name the smaller letters. But, when asked to name ink color only, and ignore letter identity, the large letter covertly affected responding. That is, when the large letter was the same as the first letter of the ink color, the patient named ink color more quickly and accurately than when the large letter was incongruent with the correct response. Moreover, when the covert global and overt local visual processing conflicted, the global letter always dominated over the local letters, despite the patient's inability to perceive it consciously. These data show that the covert processing of global visual information in simultanagnosia can dominate overt local information, even across different streams of information processing.
Topics: Aged; Agnosia; Female; Humans; Pattern Recognition, Visual; Visual Perception
PubMed: 26878160
DOI: 10.1080/13554794.2015.1137949 -
Brain Imaging and Behavior Jun 2022Simultanagnosia is a common symptom of posterior cortical atrophy, and its association with brain structural and functional changes remains unclear. In our study, 18...
Simultanagnosia is a common symptom of posterior cortical atrophy, and its association with brain structural and functional changes remains unclear. In our study, 18 posterior cortical atrophy patients with simultanagnosia, 29 patients with Alzheimer's disease and 20 cognitively normal controls were recruited and subjected to full neuropsychological evaluation, including simultanagnosia tests, and structural and resting-state functional MRI. The gray matter volume was assessed by voxel-based morphometry, while the intrinsic functional connectivity was evaluated using the reduced gray matter volume regions of interest as the seed. In contrast to the patients with Alzheimer's disease, those with posterior cortical atrophy showed the following: (1) markedly lower simultanagnosia test scores, (2) an altered regional gray matter volume of the left middle occipital gyrus and ventral occipital areas, and (3) lowered intrinsic functional connectivity with the left middle occipital gyrus, left lingual gyrus and right middle occipital gyrus separately. Additionally, the gray matter volume of the left middle occipital gyrus and left inferior occipital gyrus were each correlated with simultanagnosia in posterior cortical atrophy patients. The intrinsic functional connectivity of the left middle occipital gyrus with the right superior occipital gyrus and that of the right middle occipital gyrus with the left superior parietal gyrus were also correlated with simultanagnosia in posterior cortical atrophy patients. In summary, this study indicated that simultanagnosia is associated with gray matter reductions and decreased functional connectivity in the left middle occipital gyrus and the left inferior occipital gyrus in patients with posterior cortical atrophy.
Topics: Alzheimer Disease; Atrophy; Brain; Brain Mapping; Gray Matter; Humans; Magnetic Resonance Imaging
PubMed: 34787788
DOI: 10.1007/s11682-021-00568-8 -
Rinsho Shinkeigaku = Clinical Neurology Oct 2023A 76-year-old male patient was admitted to our hospital for the treatment of acute cerebral infarction in the right temporal stem, right lateral thalamus, and right...
A 76-year-old male patient was admitted to our hospital for the treatment of acute cerebral infarction in the right temporal stem, right lateral thalamus, and right pulvinar regions. Although his overall cognitive function was almost normal, he exhibited reduced visual sensitivity in the homonymous lower left quadrant of the visual field, left unilateral spatial neglect (USN), and simultanagnosia. Left USN improved 4 months after the onset of infarction; however, simultanagnosia persisted. To the best of our knowledge, this is the first case of simultanagnosia caused by cerebral infarction in the right temporal stem, right lateral thalamus, and right pulvinar regions.
Topics: Male; Humans; Aged; Pulvinar; Thalamus; Cerebral Infarction; Agnosia; Perceptual Disorders
PubMed: 37779025
DOI: 10.5692/clinicalneurol.cn-001846 -
Indian Journal of Ophthalmology Jan 2020Simultanagnosia resulting from dorsal stream dysfunction is an under recognized condition. In this case report we describe the case of a young woman who developed...
Simultanagnosia resulting from dorsal stream dysfunction is an under recognized condition. In this case report we describe the case of a young woman who developed posterior reversible encephalopathy syndrome (PRES), and who recovered visual acuities of 20/20 in each eye, along with normal visual fields and contrast sensitivities, yet experienced persistent symptoms of perceptual dysfunction. Detailed and systematic history taking revealed consistent visual difficulties typical of dorsal stream dysfunction. After a detailed explanation of her symptomatology and training in a range of strategies to cope, the patient experienced a great improvement in her day-to-day functioning.
Topics: Adult; Agnosia; Brain; Female; Humans; Magnetic Resonance Imaging; Posterior Leukoencephalopathy Syndrome; Vision Disorders; Visual Acuity
PubMed: 31856545
DOI: 10.4103/ijo.IJO_807_19 -
Archives of Clinical Neuropsychology :... May 2022Simultanagnosia is a rare neuropsychological symptom characterized by difficulty recognizing global structures while preserving perception of local detail. The condition...
OBJECTIVE
Simultanagnosia is a rare neuropsychological symptom characterized by difficulty recognizing global structures while preserving perception of local detail. The condition is classified into ventral and dorsal types. Clinical presentation of ventral simultanagnosia includes a reduced ability to recognize multiple visual stimuli rapidly, that is, part-by-part recognition. Here, we report a case of ventral simultanagnosia with a unique presentation; when short-duration visual stimuli were presented, the patient could perform global recognition by improving his part-by-part approach. To investigate the relationship between local and global perception bias and the duration of the present stimulus, we conducted a visual perception test using hierarchically organized Navon figures.
METHODS/RESULTS
The patient was a 62-year-old right-handed man who suffered from cerebral infarction in the right occipitotemporal lobe. He had no language dysfunction but exhibited left unilateral neglect, prosopagnosia, and ventral-type simultanagnosia. We conducted a visual perception test using the Navon figures and control figures as a visual stimulus. We randomly presented the figures for intervals of 0.2 or 20 s and let the patient report all the letters (global and/or local element) that he recognized. Global elements of the Navon letter were recognized a rate of 0% and 78.3% at intervals of 20 and 0.2 s, respectively, indicating that shorter presentation made the part-by-part approach less likely to manifest.
CONCLUSIONS
We assumed that the simultanagnosia in this case was caused by failure to maintain the initially perceived global information for a long period of time during visual presentation, due to right occipitotemporal damage.
Topics: Agnosia; Humans; Male; Middle Aged; Neuropsychological Tests; Recognition, Psychology
PubMed: 34664637
DOI: 10.1093/arclin/acab088