[Posterior cortical atrophy].

R Alberca

PubMed · 11562831

[Posterior cortical atrophy].

Abstract

INTRODUCTION: Posterior cortical atrophy (PCA) is a dementing syndrome characterized by an early alteration of higher visual functions. Patients usually develop a perceptive visual agnosia related to Balint syndrome. DEVELOPMENT: Verification showed Alzheimer s disease (AD) in most PCA observations (13/14 cases), and it can be concluded that there is a posterior variant of AD with prominent visual symptomatology. However, most PCA cases have not been verified and the nature of the disorder remains unknown in these observations. An early and severe unilateral occipital horn dilatation was found in one out of every six cases with non verified PCA. To the best of our knowledge, this image has not been described in AD and these observations could be of different nature. On the other hand, some non verified PCA cases have occasionally manifested as an associative visual agnosia. The nature of this type of associative disorder is unknown, but it could be similar to the nature of semantic dementia, a non Alzheimer s syndrome related to unspecific lesions of temporal lobes.

Explore related subjects

Agnosia Alzheimer Disease Atrophy Cerebral Cortex Dementia Frontal Lobe Humans Temporal Lobe English Abstract Journal Article

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

R Alberca. [Posterior cortical atrophy].. https://pubmed.ncbi.nlm.nih.gov/11562831/

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2007

Asymmetrical alien hands in corticobasal degeneration.

There are several forms of alien limb, but alien limb in corticobasal degeneration (CBD) is not well understood. We studied a patient with CBD who demonstrated two different types of alien limb. With his right hand he demonstrated a tactile avoidance response with levitation. With his left hand, he demonstrated continuous tactile pursuit of the examiner's hand ("tactile mitgehen"). Mitgehen is often associated with frontal dysfunction, but avoidance response and levitation are often associated with parietal dysfunction.

Agnosia↗

PubMed2007

"Sequence Agnosia" in Bálint's syndrome: defects in visuotemporal processing after bilateral parietal damage.

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. Further studies showed that this deficit was not due to impairments in sustained attention or in distributing attention over time, but to impaired processing of temporal sequences. The deficit was also present with auditory stimuli, indicating a multimodal failure of temporal sequencing. These findings show that bilateral parietal lesions affect not only the spatial but also the temporal organization of perception.

Agnosia↗

PubMed2007

[Parallel processing of motion vision].

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. She could not perceive the movement of objects, although she could walk without colliding with obstacles and could catch incoming objects. It has also been reported that patients with a bilateral parietal lesion had well-preserved primary motion vision, but had problems walking and catching a ball (Vaina, 1998). Therefore, motion for vision and motion for action might have independent mechanisms. Such dissociation has also been noted in patients with Bálint syndrome. Some patients behave like a blind person but can walk and catch a ball, while other patients bump into obstacles while walking. These results indicate that the neural bases of motion vision are distinct from those of form vision and that there are subdivisions of motion vision.

Agnosia↗