Visual agnosia

The most frequent of the primary degenerative dementias is Alzheimer's disease (AD). The gradual loss of memory and attention in patients suffering from this illness are accompanied by aphasia, apraxia, agnosia, and alterations in visual-spatial perception. This group of symptoms is completed by emotional alterations, psychic instability, and changes in personality that appear in advanced phases of the illness. Different histopathological alterations have been described, like marked atrophy of the cerebral cortex with loss of cortical and subcortical neurons...

Prosopagnosia (PA) or face blindness is characterized by a deficiency in identifying familiar faces. Almost all reports are single cases or collections of unrelated patients who acquired prosopagnosia after brain injuries, strokes or atrophy of at least the right occipito-temporal cortex. Until 2001, the inborn form - in the absence of any brain lesions - was described in fewer than 20 probands exclusively of Caucasian origin. We recently found that in the German Caucasian population, congenital prosopagnosia has a very high prevalence of at least 2...

Topographical disorientation refers to individuals who are unable to find their way around large-scale environments in a normal manner. Childhood topographical disorientation is rarely investigated or reported. Treatment of topographical disorientation is also rare with only one reported treatment study in an adult (Davis & Coltheart, 1999) and no known description of treatment in a child. This paper reports a detailed case analysis of CA, a 6-year-old child with topographical disorientation, and a description of a treatment programme focused on training orientation in the school environment...

We examined the ability of a previously well-studied patient with visual agnosia to compute the average orientation of elements in visual displays. In a structural MRI study, we show that the lesion is likely to involve a variety of ventral extra-striate areas, including V2, V3 and V4; however, the lesion does not extend dorsally. Subsequently we show that some ability to compute average orientation is spared, though there are limitations on the ability to scale the averaging process as a function of the numbers of elements...

A 72-year-old woman developed difficulty reading, driving, and playing dominoes. Ophthalmologic examination revealed a homonymous hemianopia, but brain MRI showed no abnormality to explain the visual field defect. Neuropsychiatric testing demonstrated severely impaired visual processing (simultagnosia, visual agnosia, visuospatial difficulty). Positron emission tomography revealed hypometabolism of both parietal and occipital lobes consistent with posterior cortical atrophy or the visual variant of Alzheimer disease...

Susac's syndrome is a vasospastic disease resulting from bilateral microangiopathy of the brain, cochlea and retina. It is characterized by encephalopathy, bilateral sensorineural fluctuating hearing loss and visual loss. It is very uncommon and usually affects women during young adulthood. Since all three symptoms of the triad may not be present, the clinical diagnosis is difficult. Therefore, neuroimaging, particularly magnetic resonance imaging, has an important role in establishing the diagnosis. In this case report, we present a young woman who had all the symptoms of Susac's syndrome...

PURPOSE OF REVIEW: The traditional focus of neurorehabilitaion has been on the patients' attention on their deficit, such that they should become aware of their problems and gain intentional control of compensatory strategies (descending approach). We review prism adaptation as one of the approaches that emphasize ascending rather than descending strategies to the rehabilitation of visuo-spatial disorders. The clinical outcome of prism adaptation highlights the need for a theoretical reconsideration of some previous stances to neurological rehabilitation...

OBJECTIVE: The perception of visual verticality is often perturbed after stroke and might be an underlying component of imbalance. The aim of this study was to describe the evolution of visual vertical (VV) perturbation and to investigate the factors affecting it. METHODS: Thirty patients with hemiplegia after a single hemispheric stroke (17 left lesioned [LL] and 13 right lesioned [RL]) were studied. Visual verticality was tested within 45 days of stroke, and then at 3 and 6 months...

Posterior cortical atrophy is a striking clinical syndrome in which a dementing illness begins with visual symptoms. Initially, the problem may seem to be loss of elementary vision, but over time the patient develops features of visual agnosia, topographical difficulty, optic ataxia, simultanagnosia, ocular apraxia (Balint's syndrome), alexia, acalculia, right-left confusion, and agraphia (Gerstmann's syndrome), and later a more generalized dementia. Occasional patients have visual hallucinations and signs of Parkinson's disease or Lewy body dementia...

Susac syndrome is a rare vasculopathy characterized by visual, hearing, and cognitive dysfunction. Optimal treatment is unknown, but many patients require chemotherapy to control disease activity. We describe two patients with Susac syndrome and their response to intravenous immune globulin (IVIg) and corticosteroids. Both patients improved following acute treatment with IVIg and intravenous methylprednisolone (IVMP), and no further relapses were observed. One patient showed significant improvement in hearing and MRI lesions shortly following acute treatment...

This report concerns the fragmented visual percepts in a woman, TR, following a right entorhinal-perirhinal infarct. In a previous report, Weddell [Weddell, R. A. (2005). A visual disorder producing highly selective deletion of recurring letters. Cortex, 41, 471-485] linked TR's highly selective tendency to delete recurrent letters with her fragmented percepts. The conflation of same-identity form elements was attributed to anterior extrastriate damage, which reduced the amount of information sustainable in fully resolved visual percepts, and the present experimental investigation of her subjective account of segment formation and resolution completes the story...

INTRODUCTION: The cortex of medial temporal lobe is a group of different allocortical fields which included the hippocampal formation (dentate gyrus, hippocampus proper, and subicular complex) and extrahippocampal cortices (entorhinal, perirhinal, and parahippocampal). It is widely accepted that both of them play an important role in memory process. In humans, several reports indicates that damage to the hippocampus alone would lead to a clinically significant amnesia; when the injuries are more extensive others cognitive disorders, as those related to visual sphere, make worse the clinic picture, and some of these cases were reported as associative visual agnosias...

It is now well established that the visual brain is divided into two visual streams, the ventral and the dorsal stream. Milner and Goodale have suggested that the ventral stream is dedicated for processing vision for perception and the dorsal stream vision for action [A.D. Milner & M.A. Goodale (1995) The Visual Brain in Action, Oxford University Press, Oxford]. However, it is possible that ongoing processes in the visuomotor stream will nevertheless have an effect on perceptual processes. This possibility was examined in the present study...

Patients with simultanagnosia often demonstrate 'local capture', meaning that they identify only the local elements of stimuli that contain a hierarchy of both local and global structures. Recent studies, however, have found that these patients may implicitly process the global form. We examined the general applicability of the concept of local capture, and specifically whether the global level of stimuli can be explicitly reported by patients with simultanagnosia. We tested a patient with simultanagnosia with globally biased stimuli such as hierarchical Arcimboldo faces and small, dense Navon letters...

OBJECTIVES: The study investigated if patient and informant reported Quality of Life (QoL) differed in early Alzheimer's disease (AD). In addition, we examined whether anosognosia had an impact on the agreement between patient and informant ratings of QoL and whether anosognosia, dementia severity, depression and behavioural symptoms were significantly correlated to QoL in early AD. METHODS: From a prospective research program including newly referred patients (age >60 years and MMSE > or = 20), 48 patients with very early AD were included...

Studies of neurological patients with category-specific agnosia have provided important contributions to our understanding of object recognition, although the meaning of such disorders is still hotly debated. One crucial line of research for our understanding of category effects, is through the examination of category biases in healthy normal subjects. This approach has, however, led to contradictory findings with advantages both for natural kinds and for man-made things being documented in healthy subjects...

PURPOSE OF REVIEW: To discuss whether recent functional neuroimaging results can account for clinical phenomenology in visual associative agnosias. RECENT FINDINGS: Functional neuroimaging studies in healthy human subjects have identified only two regions of ventral occipitotemporal cortex that invariantly respond to individual faces and visual words, respectively. The signature of face identity coding in the fusiform neural response was shown to be missing in a patient with prosopagnosia...

OBJECTIVE: To clinically characterize performance on the Hooper Visual Organization Test (HVOT) among participants with mild cognitive impairment (MCI) and to identify naming and executive functioning correlates associated with HVOT performance among MCI participants and normal controls (NC). BACKGROUND: The HVOT is a common neuropsychological instrument that measures visuospatial skills and agnosia. It has, however, been criticized for its multifactorial nature, as several studies have reported executive or language correlates of HVOT performance...

One major function of parietal cortex is to direct our attention towards salient stimuli. The present data suggest that it also plays an important role in visual gestalt perception. Patients with simultanagnosia following lesions in this area are not able to extract the meaning of a visual scene whereas being perfectly able to recognise individual objects of this scene. We tested two patients with simultanagnosia with hierarchical Navon figures combined with eye movements recordings. The patients' performance allowed us to compare directly the scan paths in trials in which the global letter shape was recognised with trials in which the global letter shape was not recognised...

OBJECTIVE: In posterior cortical atrophy (PCA), visual hallucinations are rare symptoms and mirror sign has not been described. METHOD: Single case report. RESULTS: We reported a 60-year-old woman with PCA who reported complex visual hallucinations, such as a man walking in her room, and mirror sign, which was the perception of a stranger staring at her when she looked into a mirror. She could not recognize images of herself in the mirror correctly, although she could recognize that a person standing next to her and the images of that person reflected in the mirror were the same person...