Visual agnosia

The psychic tonus model (Braun and colleagues, 1999, 2002, 2003, 2006) states that the left hemisphere is a "booster" of internal experience and behavior in general, and that the right hemisphere is a "dampener". Twenty-five patients with a "positive" extreme disturbance of body schema (somatoparaphrenia) and 37 patients with a "negative" disturbance of body schema (autotopagnosia or Gerstmann's syndrome), all following a unilateral parietal lesion, were found in the literature and were analyzed to test predictions from Braun's "psychic tonus" model...

BACKGROUND: A wealth of data has documented impairments in face processing in individuals with autism spectrum disorders (ASD). Recently, the suggestion has been made that these impairments may arise from abnormal development of a subcortical system involved in face processing that originates in the magnocellular pathway of the primate visual system. METHODS: To test this developmental hypothesis, we obtained visual perceptual data from 6-month-old infants who were at risk for ASD because they had an older sibling diagnosed with the disorder ("high-risk infants")...

TNFalpha plays an important role as an inflammatory mediator in both several autoimmune diseases and multiple sclerosis. Anti-TNFalpha antibody has been widely used to treat rheumatoid arthritis and Crohn's disease. On the. other hand, anti-TNFalpha antibody treatment increased recurrence rate in clinical trials for multiple sclerosis. We report a patient with rheumatoid arthritis without past history of any neurological disorders, who developed diplopia, ataxia, and visual agnosia specific to line drawing in the course of anti-TNFalpha antibody treatment...

The Klüver-Bucy syndrome (KBS) was first described in 1937 as an experimental neurobehavorial syndrome in monkeys with bitemporal brain lesions. The syndrome in man was subsequently observed to be transient or permanent in a variety of neurodegenerative disorders and after traumatic, nontraumatic, and infectious brain injury. Its most common manifestations are hyperorality with changes in dietary habits, hypersexuality, and visual agnosia. Seizures are another frequent symptom. Here we describe KBS in a female inpatient aged 30 in whom KBS and psychotic symptoms occurred together...

Kluver-Bucy syndrome is a rare neurobehavioral condition characterized by visual agnosia, excessive oral tendency, hypermetamorphosis, placidity, altered sexual behaviors, and changes in dietary habits. The authors report a case of Kluver-Bucy syndrome in a 10-year-old boy with non-Hodgkin lymphoma after intratechal methotrexate administration. He was treated by risperidone without any sequels.

Several neuropsychological studies have reported dissociation between motion vision and object vision. One patient with motion blindness had a bilateral MT/V5 lesion and could see objects, but could not see the motion of the objects (Zihl et al, 1983). By contrast, some blindsight patients with primary visual cortex lesions cannot see objects but can see their movement (e.g. Riddoch, 1917). These results imply that movement vision and form vision rely on independent mechanisms. However one patient with motion blindness had controversial symptoms concerning motion vision...

We reported double-dissociation between the visual processing of the edges and the surfaces of objects. Patients with lateral occipital damage showed selective impairment in the perception of edges whereas those with medial ventral occipital damage showed selective impairment in the perception of the 3D structure of the surface. Patients with medial ventral occipital damage also exhibited impaired perception of color, which is also a surface property. Those results were consistent with those from neuroimaging studies...

Visual experience depends critically on visual attention, which selects a particular aspect of a visual display. Recent clinical, neuroimaging, and animal studies revealed that visual attention was divided into active and passive or top-down and bottom-up attention. Although these dichotomies are clear-cut in definition, visual attention could be modulated by many factors. Detailed observation of brain-injured patients provides with evidence for dynamic and fine control of visual attention. We observed patients with dorsal simultanagnosia and that with callosal disconnection syndrome...

INTRODUCTION: Selective attention to threat-related information has been associated with clinical delusions in schizophrenia and nonclinical delusional ideation in healthy individuals. However, it is unclear whether biased attention for threat reflects early engagement effects on selective attention, or later difficulties in disengaging attention from perceived threat. The present study examined which of these processes operate in nonclinical delusion-prone individuals. METHODS: A total of 100 psychologically healthy participants completed the Peters et al...

We present a case (SE) with integrative visual agnosia following ischemic stroke affecting the right dorsal and the left ventral pathways of the visual system. Despite his inability to identify global hierarchical letters [Navon, D. (1977). Forest before trees: The precedence of global features in visual perception. Cognitive Psychology, 9, 353-383], and his dense object agnosia, SE showed normal global-to-local interference when responding to local letters in Navon hierarchical stimuli and significant picture-word identity priming in a semantic decision task for words...

Prosopagnosia is one of the many forms of visual associative agnosia, in which familiar faces lose their distinctive association. In the case of prosopagnosia, the ability to recognize familiar faces is lost, due to lesions in the medial occipitotemporal region. In "associative" prosopagnosia, the perceptual system seems adequate to allow for recognition, yet recognition cannot take place. Our hypothesis is that a possible cause of associative prosopagnosia might be the occurrence of Dynamic attractors in the brain's auto-associative circuits...

In associative agnosia early perceptual processing of faces or objects are considered to be intact, while the ability to access stored semantic information about the individual face or object is impaired. Recent claims, however, have asserted that associative agnosia is also characterized by deficits at the perceptual level, which are too subtle to be detected by current neuropsychological tests. Thus, the impaired identification of famous faces or common objects in associative agnosia stems from difficulties in extracting the minute perceptual details required to identify a face or an object...

Alzheimer's disease is associated with progressively dysfunctional gene expression in the limbic system of the brain. The thalamus and primary visual cortex are thought to be initially spared of Alzheimer-type changes that ravage the association neocortex. In this study, using DNA arrays and Western immunoassay, gene expression patterns were examined in the thalamus and primary visual cortex of moderate-stage and late-stage Alzheimer's disease and age-matched controls using a set of proinflammatory genes known to be upregulated in the temporal lobe neocortex and hippocampus of moderate-stage Alzheimer's disease...

The Gollin test (measuring recognition thresholds for fragmented line drawings of everyday objects and animals) has traditionally been regarded as a test of incomplete figure perception or 'closure', though there is a debate about how such closure is achieved. Here, figural incompleteness is considered to be the result of masking, such that absence of contour elements of a fragmented figure is the result of the influence of an 'invisible' mask. It is as though the figure is partly obscured by a mask having parameters identical to those of the background...

Existing neuropsychological tests are often complex and time-consuming. We designed a modified Mini Mental Test (MMT) battery for clinical assessment of the global and regional higher cortical functions of the brain. We tested its applicability in healthy subjects with different ethnic, cultural and educational backgrounds. The usefulness of our MMT as a tool for the clinical evaluation of patients with various forms of vascular dementia was determined. The MMT comprises five subtests, including clinical evaluations of: (A) orientation (6 points); (B) attention, right-left discrimination, speech, and calculation (20); (C) immediate recall, and recent and remote memory retrieval (10); (D) praxis (10); and (E) visuospatial orientation, agnosia, hemianopsia, and visual hemineglect (14)...

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Several neuropsychological studies have reported dissociation between motion vision and object vision. One patient with motion blindness had a bilateral MT/V5 lesion and could see objects, but could not see the motion of the objects (Zihl et al, 1983). By contrast, some blindsight patients with primary visual cortex lesions cannot see objects but can see their movement (e.g. Riddoch, 1917). These results imply that movement vision and form vision rely on independent mechanisms. However one patient with motion blindness had controversial symptoms concerning motion vision...

We reported double-dissociation between the visual processing of the edges and the surfaces of objects. Patients with lateral occipital damage showed selective impairment in the perception of edges whereas those with medial ventral occipital damage showed selective impairment in the perception of the 3D structure of the surface. Patients with medial ventral occipital damage also exhibited impaired perception of color, which is also a surface property. Those results were consistent with those from neuroimaging studies...

Visual experience depends critically on visual attention, which selects a particular aspect of a visual display. Recent clinical, neuroimaging, and animal studies revealed that visual attention was divided into active and passive or top-down and bottom-up attention. Although these dichotomies are clear-cut in definition, visual attention could be modulated by many factors. Detailed observation of brain-injured patients provides with evidence for dynamic and fine control of visual attention. We observed patients with dorsal simultanagnosia and that with callosal disconnection syndrome...

Bálint's syndrome is characterized by visuospatial dysfunction, with failure to attend to multiple objects in space and poor spatial localization manifested as impaired reaching and saccadic targeting. Less investigated in this disorder is perceptual processing along the dimension of time. We studied the performance of a patient with Bálint's syndrome on two oddity paradigms in which she had to indicate which of three objects was different in color, shape, or structure. Her initial difficulty with processing multiple objects present simultaneously in different locations recovered, but she had persistent difficulty processing objects seen sequentially at the same location...