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Annals of the New York Academy of... Mar 2015This study aims to investigate whether attention and spatiotemporal integration deficits are dissociated in patients with bilateral posterior cortical atrophy (PCA), and... (Randomized Controlled Trial)
Randomized Controlled Trial
This study aims to investigate whether attention and spatiotemporal integration deficits are dissociated in patients with bilateral posterior cortical atrophy (PCA), and whether it is their combination that leads to a severe clinical handicap. We recorded performance and ocular behavior of four PCA patients and four age-matched controls in visual search and counting tasks. We measured the percentage of targets detected and the mean detection time in a "pop-out" search. We also compared counting ability when a set of dots is presented briefly (in healthy individuals, the automatic deployment of attention over space allows a fast estimation of quantity) or for unlimited duration (favoring sequential counting, hence spatiotemporal integration). All patients showed reduced deployment of attention over space (simultanagnosia), resulting in increased visual search times and underestimations of the number of briefly presented dots. Only two patients showed ocular revisiting behavior that caused frequent omissions in visual search and overestimations of the number of dots presented for unlimited duration. The impairment to deploy attention is considered here as a bilateral covert attention deficit. Disorganized ocular exploration appears to be independent and is hypothesized to result from processes maintaining a salience map over time (spatial working memory) and especially across saccades.
Topics: Aged; Atrophy; Attention; Cerebral Cortex; Eye Movements; Female; Humans; Male; Memory Disorders; Memory, Short-Term; Middle Aged; Photic Stimulation
PubMed: 25708555
DOI: 10.1111/nyas.12731 -
International Journal of... Apr 2009We report a psychophysiological study of "recognition without awareness" in patient 2354, who had severe but circumscribed atrophy in the occipitoparietal region...
We report a psychophysiological study of "recognition without awareness" in patient 2354, who had severe but circumscribed atrophy in the occipitoparietal region bilaterally (caused by visual-variant Alzheimer's disease, documented by structural and functional neuroimaging) and an accompanying Balint syndrome that prevented her from recognizing the emotional valence of many highly charged negative visual scenes (e.g., a burned body). Despite this lack of overt recognition, patient 2354 nonetheless generated large amplitude skin conductance responses to highly charged negative pictures, demonstrating the same kind of recognition without awareness that has been reported previously in patients with bilateral occipitotemporal dysfunction and prosopagnosia [e.g., Tranel, D., & Damasio, A. R. (1985). Knowledge without awareness: an autonomic index of facial recognition by prosopagnosics. Science, 228, 1453-1454.]. Our case complements both previous evidence of covert, nonconscious recognition in patients with prosopagnosia, and previous behavioral studies of patients with Balint syndrome that have shown evidence of "preattentive" visual processing. The findings add to the small but important set of empirical observations regarding nonconscious visual processing in neurological patients, and indicate that recognition without awareness can occur in the setting of dorsal visual stream dysfunction and Balint syndrome. The findings in our patient suggest that she has patent pathways from higher-order visual cortices to autonomic effectors in the amygdala or hypothalamus, even though the results of such information processing are not made available to conscious awareness.
Topics: Analysis of Variance; Awareness; Emotions; Female; Fluorodeoxyglucose F18; Galvanic Skin Response; Humans; Magnetic Resonance Imaging; Middle Aged; Neuropsychological Tests; Pattern Recognition, Visual; Photic Stimulation; Positron-Emission Tomography; Prosopagnosia; Recognition, Psychology; Vision, Ocular
PubMed: 18824046
DOI: 10.1016/j.ijpsycho.2008.02.012 -
Neurology May 2014A 54-year-old woman developed acute hypertensive encephalopathy associated with acetaminophen-induced liver failure. Examination showed blindness with absence of...
A 54-year-old woman developed acute hypertensive encephalopathy associated with acetaminophen-induced liver failure. Examination showed blindness with absence of horizontal and vertical volitional and reflex saccades (video on the ® Web site at Neurology.org, first segment). MRI showed biparieto-occipital signal abnormalities consistent with the posterior reversible encephalopathy syndrome (PRES) (figure). Within 24 hours, visual acuity and eye movements improved, but the patient developed ocular apraxia (increased saccadic latency), optic ataxia (impaired visual navigation), and simultanagnosia (inability to recognize more than a single object): the Balint syndrome (video, second segment). This illustrates that a severe expression of oculomotor apraxia can mimic complete ophthalmoplegia and that Balint syndrome may occur at the onset and during recovery from PRES.
Topics: Brain Diseases; Female; Humans; Magnetic Resonance Imaging; Middle Aged; Occipital Lobe; Ophthalmoplegia; Parietal Lobe; Syndrome
PubMed: 24843035
DOI: 10.1212/WNL.0000000000000441 -
Frontiers in Human Neuroscience 2013Partial or complete Balint's syndrome is a core feature of the clinico-radiological syndrome of posterior cortical atrophy (PCA), in which individuals experience a...
Partial or complete Balint's syndrome is a core feature of the clinico-radiological syndrome of posterior cortical atrophy (PCA), in which individuals experience a progressive deterioration of cortical vision. Although multi-object arrays are frequently used to detect simultanagnosia in the clinical assessment and diagnosis of PCA, to date there have been no group studies of scene perception in patients with the syndrome. The current study involved three linked experiments conducted in PCA patients and healthy controls. Experiment 1 evaluated the accuracy and latency of complex scene perception relative to individual faces and objects (color and grayscale) using a categorization paradigm. PCA patients were both less accurate (faces < scenes < objects) and slower (scenes < objects < faces) than controls on all categories, with performance strongly associated with their level of basic visual processing impairment; patients also showed a small advantage for color over grayscale stimuli. Experiment 2 involved free description of real world scenes. PCA patients generated fewer features and more misperceptions than controls, though perceptual errors were always consistent with the patient's global understanding of the scene (whether correct or not). Experiment 3 used eye tracking measures to compare patient and control eye movements over initial and subsequent fixations of scenes. Patients' fixation patterns were significantly different to those of young and age-matched controls, with comparable group differences for both initial and subsequent fixations. Overall, these findings describe the variability in everyday scene perception exhibited by individuals with PCA, and indicate the importance of exposure duration in the perception of complex scenes.
PubMed: 24106469
DOI: 10.3389/fnhum.2013.00621 -
Brain : a Journal of Neurology May 2012A fundamental aspect of visual cognition is our disposition to see the 'forest before the trees'. However, damage to the posterior parietal cortex, a critical brain... (Randomized Controlled Trial)
Randomized Controlled Trial
A fundamental aspect of visual cognition is our disposition to see the 'forest before the trees'. However, damage to the posterior parietal cortex, a critical brain region along the dorsal visual pathway, can produce a neurological disorder called simultanagnosia, characterized by a debilitating inability to perceive the 'forest' but not the 'trees' (i.e. impaired global processing despite intact local processing). This impairment in perceiving the global shape persists even though the ventral visual pathway, the primary recognition pathway, is intact in these patients. Here, we enabled global processing in patients with simultanagnosia using a psychophysical technique, which allowed us to bias stimuli such that they are processed predominantly by the intact ventral visual pathway. Our findings reveal that the impairment in global processing that characterizes simultanagnosia stems from a disruption in the processing of low-spatial frequencies through the dorsal pathway. These findings advance our understanding of the relationship between visuospatial attention and perception and reveal the neural mechanism mediating the disposition to see the 'forest before the trees'.
Topics: Adult; Aged; Agnosia; Bias; Brain Injuries; Brain Mapping; Contrast Sensitivity; Female; Fluorodeoxyglucose F18; Humans; Male; Parietal Lobe; Photic Stimulation; Positron-Emission Tomography; Psychophysics; Psychophysiologic Disorders; Visual Pathways; Young Adult
PubMed: 22418740
DOI: 10.1093/brain/aws066 -
Internal Medicine (Tokyo, Japan) Feb 2024A 73-year-old woman with posterior cortical atrophy (PCA) presented with progressive apperceptive visual agnosia, alexia, agraphia, ventral simultanagnosia,...
A 73-year-old woman with posterior cortical atrophy (PCA) presented with progressive apperceptive visual agnosia, alexia, agraphia, ventral simultanagnosia, prosopagnosia, and allocentric (stimulus-centered) left-sided hemispatial neglect. All of these symptoms were attributed to damage to the bilateral occipito-temporal cortices, consistent with ventral variant PCA. While the Pittsburgh compound B uptake was extensively distributed throughout the occipito-parietal (dorsal) and occipito-temporal (ventral) areas, the THK5351 (ligand binding to tau aggregates/astrocyte gliosis) accumulation was limited to the ventral area. These findings suggest that local accumulation of tau proteins and/or astrocyte gliosis over the occipito-temporal cortices can result in ventral variant PCA.
PubMed: 38369357
DOI: 10.2169/internalmedicine.2844-23 -
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 -
Investigative Ophthalmology & Visual... Sep 2020Posterior cortical atrophy (PCA) is a rare neurodegenerative syndrome manifesting with visuospatial processing impairment. We recently suggested that abnormal population...
PURPOSE
Posterior cortical atrophy (PCA) is a rare neurodegenerative syndrome manifesting with visuospatial processing impairment. We recently suggested that abnormal population receptive field properties are associated with the symptoms of PCA patients. Specifically, simultanagnosia, the inability to perceive multiple items simultaneously, can be explained by smaller peripheral population receptive fields, and foveal crowding, in which nearby distractors interfere with object perception, may result from larger foveal population receptive fields. These effects occurred predominantly in V1, even though atrophy mainly involves high-order areas. In this study, we used connective field modeling to better understand these inter-area interactions.
METHODS
We used functional magnetic resonance imaging to scan six PCA patients and eight controls while they viewed drifting bar stimuli. Resting-state data were also collected. Connective field modeling was applied for both conditions: once when the source was V1 and the targets were extrastriate areas and once for the opposite direction. The difference between the two was defined as convergence magnitude.
RESULTS
With stimulus, the convergence magnitude of the controls increased along the visual pathway, suggesting that spatial integration from V1 becomes larger up the visual hierarchy. No such slope was found in the PCA patients. The difference between the groups originated mainly from the dorsal pathway. Without stimulus, the convergence magnitude was negative, slightly more so for the PCA patients, with no slope, suggesting constant divergence along the visual hierarchy.
CONCLUSIONS
Atrophy in one part of the visual system can affect other areas within the network through complex intervisual area interactions, resulting in modulation of population receptive field properties and an ensemble of visuocognitive function impairments.
Topics: Atrophy; Brain Mapping; Female; Gray Matter; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Neurodegenerative Diseases; Visual Cortex; Visual Pathways
PubMed: 32897377
DOI: 10.1167/iovs.61.11.8 -
American Journal of Alzheimer's Disease... Sep 2013Alzheimer's disease (AD) is characterized by amnesia, though non-memory-cognitive domains like visual are also affected. We planned to study frequency of visual...
INTRODUCTION
Alzheimer's disease (AD) is characterized by amnesia, though non-memory-cognitive domains like visual are also affected. We planned to study frequency of visual dysfunctions in AD and their relationship with dementia severity.
MATERIALS AND METHODS
This study was conducted in the Cognitive clinic of Department of Neurology, Bangur Institute of Neurosciences, Kolkata, between January 2007 and December 2010. 55 patients of AD were evaluated by neurological and neuropsychological assessments and by special tests for visual dysfunctions.
RESULTS
Common visual dysfunctions were visuo-constructional (87.3%), visuo-perceptual (63.6%), object agnosia(47.3%), prosopagnosia (45.5%), visual hallucination (27.3%) and simultanagnosia (12.7%). Symptoms of ventral visual pathway dysfunction were more common than that of dorsal pathway. MMSE score and number of visual manifestations had a good correlation.
CONCLUSIONS
Visual dysfunctions are common in AD, elicitation of which helps us to understand the cause of disability so that appropriate steps can be taken.
Topics: Aged; Aged, 80 and over; Agnosia; Alzheimer Disease; Ambulatory Care Facilities; Cross-Sectional Studies; Disability Evaluation; Female; Hallucinations; Humans; India; Male; Middle Aged; Neuropsychological Tests; Prosopagnosia; Visual Pathways; Visual Perception
PubMed: 23823144
DOI: 10.1177/1533317513494448 -
Frontiers in Neuroscience 2024Posterior Cortical Atrophy (PCA) is a syndrome characterized by a progressive decline in higher-order visuospatial processing, leading to symptoms such as space...
INTRODUCTION
Posterior Cortical Atrophy (PCA) is a syndrome characterized by a progressive decline in higher-order visuospatial processing, leading to symptoms such as space perception deficit, simultanagnosia, and object perception impairment. While PCA is primarily known for its impact on visuospatial abilities, recent studies have documented language abnormalities in PCA patients. This study aims to delineate the nature and origin of language impairments in PCA, hypothesizing that language deficits reflect the visuospatial processing impairments of the disease.
METHODS
We compared the language samples of 25 patients with PCA with age-matched cognitively normal (CN) individuals across two distinct tasks: a visually-dependent picture description and a visually-independent job description task. We extracted word frequency, word utterance latency, and spatial relational words for this comparison. We then conducted an in-depth analysis of the language used in the picture description task to identify specific linguistic indicators that reflect the visuospatial processing deficits of PCA.
RESULTS
Patients with PCA showed significant language deficits in the visually-dependent task, characterized by higher word frequency, prolonged utterance latency, and fewer spatial relational words, but not in the visually-independent task. An in-depth analysis of the picture description task further showed that PCA patients struggled to identify certain visual elements as well as the overall theme of the picture. A predictive model based on these language features distinguished PCA patients from CN individuals with high classification accuracy.
DISCUSSION
The findings indicate that language is a sensitive behavioral construct to detect visuospatial processing abnormalities of PCA. These insights offer theoretical and clinical avenues for understanding and managing PCA, underscoring language as a crucial marker for the visuospatial deficits of this atypical variant of Alzheimer's disease.
PubMed: 38379764
DOI: 10.3389/fnins.2024.1342909