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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 -
Practical Neurology Jun 2016The dorsal visual stream, often referred to as the 'where' stream, represents the pathway taken by visual information from the primary visual cortex to the posterior... (Review)
Review
The dorsal visual stream, often referred to as the 'where' stream, represents the pathway taken by visual information from the primary visual cortex to the posterior parietal lobe and onwards. It partners the ventral or 'what' stream, the subject of a previous review and largely a temporal-based system. Here, we consider the dorsal stream disorders of perception (simultanagnosia, akinetopsia) along with their consequences on action (eg, optic ataxia and oculomotor apraxia, along with Balint's syndrome). The role of the dorsal stream in blindsight and hemispatial neglect is also considered.
Topics: Apraxias; Humans; Parietal Lobe; Perceptual Disorders; Vision, Ocular; Visual Cortex; Visual Pathways; Visual Perception
PubMed: 26786007
DOI: 10.1136/practneurol-2015-001168 -
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 -
American Journal of Physical Medicine &... Mar 2016A 66-yr-old man with a history of atrial fibrillation and a pacemaker developed sudden onset confusion, disorientation, and visual disturbance without motor weakness....
A 66-yr-old man with a history of atrial fibrillation and a pacemaker developed sudden onset confusion, disorientation, and visual disturbance without motor weakness. Clinically, significant deficits were found in reading (alexia) and simultaneous multiobject perception (simultanagnosia), both of which the patient denied limitation in, and in vision-right hemianopsia-which he readily acknowledged. Visual acuity in the left visual field was normal. The patient also demonstrated a symptom of optic ataxia-a lack of coordination between visual inputs and hand movements-a deficit he also acknowledged. Work-up with computed topography revealed a left posterior cerebral artery infarct affecting the occipital lobe and extending to involve the parietal lobe and the splenium of the corpus callosum. The authors describe and discuss this fascinating case-the first case to their knowledge of a double disassociation of anosognosia for alexia and simultanagnosia but full, indeed quantitative, awareness of hemianopsia and optic ataxia. This case may be informative on the mechanism of anosognosia in general and supports intentional feed-forward and exemplar reafference models. With regard to the rehabilitation process, appreciation that a patient has anosognosia for various deficits is crucial in recovery and health maintenance.
Topics: Aged; Agnosia; Ataxia; Cerebral Infarction; Dyslexia; Hemianopsia; Humans; Male; Ocular Motility Disorders
PubMed: 26368835
DOI: 10.1097/PHM.0000000000000380 -
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 -
Neurocase 2016We report a patient with ventral simultanagnosia, prosopagnosia for "unfamiliar faces" (dorsal prosopagnosia), spatial agraphia, and constructional disorder,...
We report a patient with ventral simultanagnosia, prosopagnosia for "unfamiliar faces" (dorsal prosopagnosia), spatial agraphia, and constructional disorder, particularly on the left spatial side, due to a lesion in the right posterior superior and middle temporal gyri and angular gyrus. The patient showed impairment of fundamental visual and visuospatial recognition, such as in object size, configuration, and horizontal point location, which probably underlay the mechanism of simultanagnosia and prosopagnosia. This case also suggests that the coexistence of simultanagnosia and prosopagnosia results from a right hemispheric insult, and damage to the temporoparietal area interrupts the incorporation of spatial information into object recognition. This disconnection of information flow, together with impaired object recognition per se, may impair the parallel processing of multiple objects, leading to object-by-object or part-by-part recognition.
Topics: Aged; Agnosia; Brain Injuries; Face; Female; Humans; Neuropsychological Tests; Parietal Lobe; Prosopagnosia; Temporal Lobe
PubMed: 26207875
DOI: 10.1080/13554794.2015.1066827 -
Brain Imaging and Behavior Sep 2016Visuospatial abilities are sensitive to age-related decline, although the neural basis for this decline (and its everyday behavioral correlates) is as yet poorly...
Visuospatial abilities are sensitive to age-related decline, although the neural basis for this decline (and its everyday behavioral correlates) is as yet poorly understood. fMRI was employed to examine age-related differences in patterns of functional activation that underlie changes in visuospatial processing. All participants completed a brief neuropsychological battery and also a figure ground task (FGT) assessing visuospatial processing while fMRI was recorded. Participants included 16 healthy older adults (OA; aged 69-82 years) and 16 healthy younger adults (YA; aged 20-35 years). We examined age-related differences in behavioral performance on the FGT in relation to patterns of fMRI activation. OA demonstrated reduced performance on the FGT task and showed increased activation of supramarginal parietal cortex as well as increased activation of frontal and temporal regions compared to their younger counterparts. Performance on the FGT related to increased supramarginal gyrus activity and increased medial prefrontal activity in OAs, but not YAs. Our results are consistent with an anterior-posterior compensation model. Successful FGT performance requires the perception and integration of multiple stimuli and thus it is plausible that healthy aging may be accompanied by changes in visuospatial processing that mimic a subtle form of dorsal simultanagnosia. Overall, decreased visuospatial processing in OA relates to an altered frontoparietal neurobiological signature that may contribute to the general phenomenon of increasingly fragmented execution of behavior associated with normal aging.
Topics: Adult; Aged; Aged, 80 and over; Aging; Attention; Brain Mapping; Cerebrovascular Circulation; Humans; Magnetic Resonance Imaging; Male; Neuropsychological Tests; Oxygen; Parietal Lobe; Prefrontal Cortex; Reaction Time; Space Perception; Temporal Lobe; Young Adult
PubMed: 26195153
DOI: 10.1007/s11682-015-9428-y -
BMC Ophthalmology Jun 2015Prominent visual symptoms can present in the visual variant of Alzheimer's disease (VVAD). Ophthalmologists have a significant role to play in the early diagnosis of...
BACKGROUND
Prominent visual symptoms can present in the visual variant of Alzheimer's disease (VVAD). Ophthalmologists have a significant role to play in the early diagnosis of VVAD.
METHODS
We retrospectively reviewed the files of ten consecutive patients diagnosed with VVAD. All patients had a full neuro-ophthalmologic examination, a formal neurological and neuro-psychological testing, and cerebral MRI to confirm diagnosis. In addition, functional neuroimaging was obtained in seven patients.
RESULTS
The common primary symptom at presentation with all patients was difficulty with near vision (reading difficulty n = 8, "visual blur" in near vision n = 2), and difficulty writing (n = 3). Following assessment, impaired reading and writing skills were evident in 9/10 and 8/10 patients respectively. Median distance visual acuity was 20/25 and at near the median visual acuity was J6. Partial homonymous visual field defect was detected in 80 % (8/10) of the patients. Color vision was impaired in all patients when tested with Ishihara pseudoisochromatic plates, but simple color naming was normal in 8/9 tested patients. Simultanagnosia was present in 8/10 patients. Vision dysfunction corresponded with cerebral MRI findings where parieto-occipital cortical atrophy was observed in all patients. PET scan (5 patients) or SPECT (2 patients) revealed parieto-occipital dysfunction (hypometabolism or hypoperfusion) in all 7 tested patients
CONCLUSIONS
Visual difficulties are prominent in VVAD. Dyslexia, incomplete homonymous hemianopia, preserved color identification with abnormal color vision on Ishihara, and simultanagnosia were all symptoms observed frequently in this patient series. Ophthalmologists should be aware of the possibility of neurodegenerative disorders such as VVAD in patients with unexplained visual complaints, in particular reading difficulties.
Topics: Aged; Aged, 80 and over; Alzheimer Disease; Atrophy; Color Vision Defects; Early Diagnosis; Female; Hemianopsia; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Occipital Lobe; Parietal Lobe; Retrospective Studies; Visual Acuity; Visual Field Tests; Visual Fields
PubMed: 26122482
DOI: 10.1186/s12886-015-0060-9 -
Cortex; a Journal Devoted To the Study... Aug 2015Although it has been proposed that visuospatial working memory may be impaired in Bálint syndrome patients, neither a systematic study concerning this proposal nor a...
Although it has been proposed that visuospatial working memory may be impaired in Bálint syndrome patients, neither a systematic study concerning this proposal nor a comparison with patients having right-parietal damage has been made. Visuospatial working memory was assessed for six Bálint syndrome patients and members of two control groups-one composed of individuals with right-parietal damage (n = 15) and a second of age- and gender-matched healthy individuals (n = 26). We placed special emphasis on patients with a mild form of Bálint syndrome who can judge positional relationships between two objects. First, the participants were subjected to delayed visuospatial matching tasks. Next, their visuospatial-temporal integration abilities were assessed using a shape-from-moving-dots task. Visuospatial working memory was impaired for Bálint syndrome patients compared with controls according to the results of the tests. The differences between the Bálint syndrome and control subjects remained when only data for patients with the mild form of Bálint syndrome were included. We conclude that visuospatial working memory may be severely impaired in Bálint syndrome patients and, therefore, might influence their inability to properly execute movements and behaviours associated with daily living.
Topics: Aged; Brain Diseases; Female; Humans; Male; Memory Disorders; Memory, Short-Term; Middle Aged; Parietal Lobe; Pattern Recognition, Visual; Space Perception; Syndrome; Visual Perception
PubMed: 26117797
DOI: 10.1016/j.cortex.2015.05.023 -
Journal of Neurology Jun 2015The purpose of this study was to identify the clinical, [(18)F]-fluorodeoxyglucose positron emission tomography (FDG-PET) and amyloid-PET findings in a large cohort of...
The purpose of this study was to identify the clinical, [(18)F]-fluorodeoxyglucose positron emission tomography (FDG-PET) and amyloid-PET findings in a large cohort of posterior cortical atrophy (PCA) patients, to examine the neural correlates of the classic features of PCA, and to better understand the features associated with early PCA. We prospectively recruited 25 patients who presented to the Mayo Clinic between March 2013 and August 2014 and met diagnostic criteria for PCA. All patients underwent a standardized set of tests and amyloid imaging with [(11)C] Pittsburg compound B (PiB). Seventeen (68 %) underwent FDG-PET scanning. We divided the cohort at the median disease duration of 4 years in order to assess clinical and FDG-PET correlates of early PCA (n = 13). The most common clinical features were simultanagnosia (92 %), dysgraphia (68 %), poly-mini-myoclonus (64 %) and oculomotor apraxia (56.5 %). On FDG-PET, hypometabolism was observed bilaterally in the lateral and medial parietal and occipital lobes. Simultanagnosia was associated with hypometabolism in the right occipital lobe and posterior cingulum, optic ataxia with hypometabolism in left occipital lobe, and oculomotor apraxia with hypometabolism in the left parietal lobe and posterior cingulate gyrus. All 25 PCA patients were amyloid positive. Simultanagnosia was the only feature present in 85 % of early PCA patients. The syndrome of PCA is associated with posterior hemisphere hypometabolism and with amyloid deposition. Many of the classic features of PCA show associated focal, but not widespread, areas of involvement of these posterior hemispheric regions. Simultanagnosia appears to be the most common and hence sensitive feature of early PCA.
Topics: Aged; Amyloid; Aniline Compounds; Atrophy; Brain; Brain Mapping; Carbon Isotopes; Cohort Studies; Female; Fluorodeoxyglucose F18; Humans; Male; Middle Aged; Neurologic Examination; Positron-Emission Tomography; Thiazoles; Tomography, X-Ray Computed
PubMed: 25862483
DOI: 10.1007/s00415-015-7732-5