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Frontiers in Psychology 2015In combination with whole report and partial report tasks, the theory of visual attention (TVA) can be used to estimate individual differences in five basic attentional... (Review)
Review
In combination with whole report and partial report tasks, the theory of visual attention (TVA) can be used to estimate individual differences in five basic attentional parameters: the visual processing speed, the storage capacity of visual short-term memory, the perceptual threshold, the efficiency of top-down selectivity, and the spatial bias of attentional weighting. TVA-based assessment has been used in about 30 studies to investigate attentional deficits in a range of neurological and psychiatric conditions: (a) neglect and simultanagnosia, (b) reading disturbances, (c) aging and neurodegenerative diseases, and most recently (d) neurodevelopmental disorders. The article introduces TVA based assessment, discusses its methodology and psychometric properties, and reviews the progress made in each of the four research fields. The empirical results demonstrate the general usefulness of TVA-based assessment for many types of clinical neuropsychological research. The method's most important qualities are cognitive specificity and theoretical grounding, but it is also characterized by good reliability and sensitivity to minor deficits. The review concludes by pointing to promising new areas for clinical TVA-based research.
PubMed: 25852607
DOI: 10.3389/fpsyg.2015.00290 -
Cerebral Cortex (New York, N.Y. : 1991) Mar 2016Simultanagnosia is a deficit in which patients are unable to perceive multiple objects simultaneously. To date, it remains disputed whether this deficit results from...
Simultanagnosia is a deficit in which patients are unable to perceive multiple objects simultaneously. To date, it remains disputed whether this deficit results from disrupted object or space perception. We asked both healthy participants as well as a patient with simultanagnosia to perform different visual search tasks of variable difficulty. We also modulated the number of objects (target and distracters) presented. For healthy participants, we found that each visual search task was performed with a specific "attentional field" depending on the difficulty of visual object processing but not on the number of objects falling within this "working space." This was demonstrated by measuring the cost in reaction times using different gaze-contingent visible window sizes. We found that bilateral damage to the superior parietal lobule impairs the spatial integration of separable features (within-object processing), shrinking the attentional field in which a target can be detected, but causing no deficit in processing multiple objects per se.
Topics: Adult; Attention; Brain Ischemia; Female; Humans; Parietal Lobe; Perceptual Disorders; Photic Stimulation; Psychological Tests; Reaction Time; Space Perception; Stroke; Visual Perception
PubMed: 25840422
DOI: 10.1093/cercor/bhv059 -
Journal of Cognitive Neuroscience Aug 2015The neuropsychological syndrome "simultanagnosia" is characterized by the inability to integrate local elements into a global entity. This deficit in Gestalt perception...
The neuropsychological syndrome "simultanagnosia" is characterized by the inability to integrate local elements into a global entity. This deficit in Gestalt perception is mainly apparent for novel global structures administered in clinical tests or unfamiliar visual scenes. Recognition of familiar complex objects or well-known visual scenes is often unaffected. Recent neuroimaging studies and reports from simultanagnosia patients suggest a crucial involvement of temporoparietal brain areas in processing of hierarchically organized visual material. In this study, we investigated the specific role of the TPJ in Gestalt perception. On the basis of perceptual characteristics known from simultanagnosia, we hypothesized that TPJ is dominantly involved in processing of novel object arrangements. To answer this question, we performed a learning study with hierarchical stimuli and tested behavioral and neuronal characteristics of Gestalt perception pre- and posttraining. The study included 16 psychophysical training sessions and two neuroimaging sessions. Participants improved their behavioral performance for trained global stimuli and showed limited transfer to untrained global material. We found significant training dependent neuronal signal modulations in anterior right hemispheric TPJ regions. These activation changes were specific to trained global stimuli, whereas no systematic neuronal response changes were observed for recognition of untrained global stimuli, local elements and regular objects that served as control stimuli. In line with perceptual characteristics in simultanagnosia, the results argue for an involvement of TPJ in processing of novel global structures. We discuss the signal modulations in the context of a more efficient or different neuronal strategy to process familiar global stimuli.
Topics: Adult; Brain; Brain Mapping; Eye Movement Measurements; Female; Humans; Learning; Magnetic Resonance Imaging; Male; Neuropsychological Tests; Photic Stimulation; Visual Perception
PubMed: 25811709
DOI: 10.1162/jocn_a_00809 -
Der Nervenarzt Jul 2015The syndrome of posterior cortical atrophy (PCA) is a rare clinical manifestation of several neurodegenerative diseases which affect the parieto-occipital cortex. The...
The syndrome of posterior cortical atrophy (PCA) is a rare clinical manifestation of several neurodegenerative diseases which affect the parieto-occipital cortex. The most frequent underlying pathology is Alzheimer's disease but some cases are caused by Lewy body disease, progressive subcortical gliosis, corticobasal degeneration or prion diseases. The most prominent clinical feature of PCA is complex visual disturbances including object agnosia, simultanagnosia, optical ataxia and oculomotor apraxia while basic visual functions remain intact. These deficits lead to multiple impairments in activities of daily living that require visual control. On progression of the disease amnestic, apraxic and dysexecutive symptoms occur so that a global dementia gradually emerges. At the core of the diagnostic work-up are a detailed patient history, accurate analysis of behavior and neuropsychological testing. Structural and functional brain imaging are suitable to demonstrate the localization of the disease process. Measurement of cerebrospinal fluid proteins (e.g. beta amyloid, tau, phospho-tau and 14-3-3) serves to confirm or exclude Alzheimer's disease or prion diseases. The mainstay of treatment are non-pharmacological interventions to support activities of daily living and personal independence. These treatments include cognitive training and compensatory strategies which can be prescribed as neuropsychological treatment or occupational therapy. If Alzheimer's disease or Lewy body disease is the likely cause, a treatment with cholinesterase inhibitor may be tried. Caregiver education and support are another essential part of the treatment regimen as with all forms of dementia.
Topics: Atrophy; Brain; Cholinesterase Inhibitors; Cognitive Behavioral Therapy; Combined Modality Therapy; Humans; Neurodegenerative Diseases; Occupational Therapy; Vision Disorders
PubMed: 25791802
DOI: 10.1007/s00115-015-4265-1 -
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 -
Neuropsychologia Mar 2015The complete loss of binocular depth perception ("flat vision") was first thoroughly described by Holmes and Horrax (1919), and has been occasionally reported thereafter...
The complete loss of binocular depth perception ("flat vision") was first thoroughly described by Holmes and Horrax (1919), and has been occasionally reported thereafter in patients with bilateral posterior-parietal lesions. Though partial spontaneous recovery occurred in some cases, the precise cause(s) of this condition remained obscure for almost a century. Here, we describe a unique patient (EH) with a large right-sided occipito-parietal hemorrhage showing a complete loss of visual depth perception for several months post-stroke. EH could well simultaneously describe multiple visual objects - hence did not show simultanagnosia - but at the same time was completely unable to estimate their distance from him. In every 3-D visual scene objects appeared equidistant to him, thus experiencing a total loss of depth perception ("flat vision"). Neurovisual assessments revealed normal functions of the eyes. EH showed bilateral lower field loss and a severely impaired binocular convergent fusion, but preserved stereopsis. Perceptual re-training of binocular fusion resulted in a progressive and finally complete recovery of objective binocular fusion values and subjective binocular depth perception in a far-to-near-space, gradient-like manner. In parallel, visual depth estimation of relative distances improved, whereas stereopsis remained unchanged. Our results show that a complete loss of 3-D depth perception can result from an isolated impairment in binocular fusion. On a neuroanatomical level, this connection could be explained by a selective lesion of area V6/V6A in the medial occipito-parietal cortex that has been associated with the integration of visual space coordinates and sustained eye-positions into a cyclopean visual 3-D percept.
Topics: Cerebral Hemorrhage; Depth Perception; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Neuropsychological Tests; Occipital Lobe; Parietal Lobe; Perceptual Disorders; Recovery of Function; Stroke; Stroke Rehabilitation; Vision Disorders; Vision Tests; Vision, Binocular
PubMed: 25619849
DOI: 10.1016/j.neuropsychologia.2015.01.029 -
Practical Neurology Feb 2015Posterior cortical atrophy (PCA) is a neurodegenerative syndrome dominated by deterioration of higher visual function (particularly visuospatial and visuoperceptual... (Review)
Review
Posterior cortical atrophy (PCA) is a neurodegenerative syndrome dominated by deterioration of higher visual function (particularly visuospatial and visuoperceptual abilities). It is most commonly due to Alzheimer's disease pathology, but may also be caused by dementia with Lewy bodies, corticobasal degeneration or Creutzfeldt-Jakob disease. Patients often present to optometrists, ophthalmologists and/or neurologists with non-specific visual complaints, and unless clinicians seek the specific symptoms and signs of PCA (beyond that of the 'standard' neurological examination), this infrequent disorder is easily missed, delaying its diagnosis and treatment. We review the clinical features of PCA, focusing on its visual manifestations, to help neurologists recognise this important syndrome.
Topics: Alzheimer Disease; Atrophy; Brain Diseases; Cerebral Cortex; Delayed Diagnosis; Female; Humans; Middle Aged
PubMed: 25216669
DOI: 10.1136/practneurol-2014-000883 -
Continuum (Minneapolis, Minn.) Aug 2014This article reviews the various types of visual dysfunction that can result from lesions of the cerebral regions beyond the striate cortex.
PURPOSE OF REVIEW
This article reviews the various types of visual dysfunction that can result from lesions of the cerebral regions beyond the striate cortex.
RECENT FINDINGS
Patients with dyschromatopsia can exhibit problems with color constancy. The apperceptive form of prosopagnosia is associated with damage to posterior occipital and fusiform gyri, and an associative/amnestic form is linked to damage to more anterior temporal regions. Pure alexia can be accompanied by a surface dysgraphia. New word-length effect criteria distinguish pure alexia from hemianopic dyslexia. Subtler problems with perception of numbers and faces can be seen in patients with pure alexia as well. Also, a developmental form of topographic disorientation, which is due to problems with forming cognitive maps of the environment, has been discovered. In Balint syndrome, added features of decreased flexibility of attention in simultanagnosia include local and global capture. Balint syndrome can affect not just localization in space, but also in time, as manifest in sequence agnosia.
SUMMARY
Lesions at intermediate levels of a processing hierarchy can cause difficulty with color perception or motion perception. At a higher level, ventral lesions of the occipitotemporal lobes can lead to a variety of problems with object recognition. Dorsal lesions of the occipitoparietal lobes can cause difficulty with spatial localization and guidance.
Topics: Adult; Aged; Female; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Perceptual Disorders; Vision Disorders; Visual Cortex; Visual Pathways; Visual Perception
PubMed: 25099101
DOI: 10.1212/01.CON.0000453311.29519.67 -
Tremor and Other Hyperkinetic Movements... 2014Posterior cortical atrophy is a clinical syndrome that is characterized by the progressive loss of visuospatial integration and is associated with neurodegenerative...
BACKGROUND
Posterior cortical atrophy is a clinical syndrome that is characterized by the progressive loss of visuospatial integration and is associated with neurodegenerative conditions.
CASE REPORT
We describe a 60-year-old female with simultanagnosia, oculomotor apraxia, and optic ataxia for which she received an initial clinical diagnosis of posterior cortical atrophy. Three years later, she developed Balint's syndrome, Gerstmann's syndrome, left alien hand syndrome, smooth asymmetric (left) rigidity, cortical sensory loss, and spontaneous myoclonic jerks of the left arm, which suggested a final diagnosis of corticobasal syndrome.
DISCUSSION
This case report indicates that corticobasal syndrome may present with visuospatial deficits.
PubMed: 25009764
DOI: 10.7916/D81G0JCQ -
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