Book Description
Brain damage may sometimes cause specific impairments in human behaviour. One rare impairment is the failure to recognize everyday objects by sight, a problem which is termed "visual agnosia". In this book, the authors discuss the case of a patient, John, who suffered from visual agnosia. ... Read more

Book Description
The cognitive neuroscience of human vision draws on two kinds of evidence: functional imaging of normal subjects and the study of neurological patients with visual disorders. Martha Farah's landmark 1990 book Visual Agnosia presented the first comprehensive analysis of disorders of visual recognition within the framework of cognitive neuroscience, and remains the authoritative work on the subject. This long-awaited second edition provides a reorganized and updated review of the visual agnosias, incorporating the latest research on patients with insights from the functional neuroimaging literature. Visual agnosia refers to a multitude of different disorders and syndromes, fascinating in their own right and valuable for what they can tell us about normal human vision. Some patients cannot recognize faces but can still recognize other objects, while others retain only face recognition. Some see only one object at a time; others can see multiple objects but recognize only one at a time. Some do not consciously perceive the orientation of an object but nevertheless reach for it with perfected oriented grasp; others do not consciously recognize a face as familiar but nevertheless respond to it autonomically. Each disorder is illustrated with a clinical vignette, followed by a thorough review of the case report literature and a discussion of the theoretical implications of the disorder for cognitive neuroscience.

The second edition extends the range of disorders covered to include disorders of topographic recognition, and both general and selective disorders of semantic memory, as well as expanded coverage of face recognition impairments. Also included are a discussion of the complementary roles of imaging and patient-based research in cognitive neuroscience, and a final integrative chapter presenting the "big picture" of object recognition as illuminated by agnosia research. ... Read more

Book Description
This digital document is a journal article from Neuropsychologia, published by Elsevier in 2006. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

Description:
The current dominant view of the visual system is marked by the functional and anatomical dissociation between a ventral stream specialised for perception and a dorsal stream specialised for action. The ''double-dissociation'' between visual agnosia (VA), a deficit of visual recognition, and optic ataxia (OA), a deficit of visuo-manual guidance, considered as consecutive to ventral and dorsal damage, respectively, has provided the main argument for this dichotomic view. In the first part of this paper, we show that the currently available empirical data do not suffice to support a double-dissociation between OA and VA. In the second part, we review evidence coming from human neuropsychology and monkey data, which cast further doubts on the validity of a simple double-dissociation between perception and action because they argue for a far more complex organisation with multiple parallel visual-to-motor connections:1.A dorso-dorsal pathway (involving the most dorsal part of the parietal and pre-motor cortices): for immediate visuo-motor control-with OA as typical disturbance. The latest research about OA is reviewed, showing how these patients exhibit deficits restricted to the most direct and fast visuo-motor transformations. We also propose that mild mirror ataxia, consisting of misreaching errors when the controlesional hand is guided to a visual goal though a mirror, could correspond to OA with an isolated ''hand effect''. 2.A ventral stream-prefrontal pathway (connections from the ventral visual stream to pre-frontal areas, by-passing the parietal areas): for ''mediate'' control (involving spatial or temporal transpositions [Rossetti, Y., & Pisella, L. (2003). Mediate responses as direct evidence for intention: Neuropsychology of Not to-, Not now- and Not there-tasks. In S. Johnson (Ed.), Cognitive Neuroscience perspectives on the problem of intentional action (pp. 67-105). MIT Press.])-with VA as typical disturbance. Preserved visuo-manual guidance in patients with VA is restricted to immediate goal-directed guidance, they exhibit deficits for delayed or pantomimed actions. 3.A ventro-dorsal pathway (involving the more ventral part of the parietal lobe and the pre-motor and pre-frontal areas): for complex planning and programming relying on high representational levels with a more bilateral organisation or an hemispheric lateralisation-with mirror apraxia, limb apraxia and spatial neglect as representatives. Mirror apraxia is a deficit that affects both hands after unilateral inferior parietal lesion with the patients reaching systematically and repeatedly toward the virtual image in the mirror. Limb apraxia is localized on a more advanced conceptual level of object-related actions and results from deficient integrative, computational and ''working memory'' capacities of the left inferior parietal lobule. A component of spatial working memory has recently been revealed also in spatial neglect consecutive to lesion involving the network of the right inferior parietal lobule and the right frontal areas. We conclude by pointing to the differential temporal constraints and integrative capabilities of these parallel visuo-motor pathways as keys to interpret the neuropsychological deficits. ... Read more

Book Description
This digital document is a journal article from Brain and Cognition, published by Elsevier in 2004. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

Description:
Two little noticed cases in which William Macewen used symptoms of visual agnosia to plan brain surgery on the angular gyrus are reviewed and evaluated. Following a head injury, Macewen's first patient had an immediate and severe visual object agnosia that lasted for about 2 weeks. After that he gradually became homicidal and depressed and it was for those symptoms that Macewen first saw him, some 11 months after the accident. From his examination, Macewen concluded that the agnosia clearly indicated a lesion in ''the posterior portion of the operculum or in the angular gyrus.'' When he removed parts of the internal table that had penetrated those structures the homicidal impulses disappeared. Macewen's second patient was seen for a chronic middle ear infection and, although neither aphasic nor deaf, was 'word deaf.' Slightly later he became 'psychically blind' as well. Macewen suspected a cerebral abscess pressing on both the angular gyrus and the first temporal convolution. A large subdural abscess was found there and the symptoms disappeared after it was treated. The patients are discussed and Macewen's positive results analysed in the historical context of the dispute over the proposed role of the angular gyrus as the visual centre. ... Read more

Book Description
This digital document is a journal article from Brain and Language, published by Elsevier in . The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

Description:
The role of sensory-motor representations in object recognition was investigated in experiments involving AD, a patient with mild visual agnosia who was impaired in the recognition of visually presented living as compared to non-living entities. AD named visually presented items for which sensory-motor information was available significantly more reliably than items for which such information was not available; this was true when all items were non-living. Naming of objects from their associated sound was normal. These data suggest that both information about object form computed in the ventral visual system as well as sensory-motor information specifying the manner of manipulation contribute to object recognition. ... Read more

Book Description
This digital document is a journal article from Neuropsychologia, published by Elsevier in 2007. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

Description:
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. In the present study, we report the case of a patient DBO with a left occipital infarct, who shows impaired object and famous face recognition. Despite his disability, he exhibits a face inversion effect, and is able to select a famous face from among non-famous distractors. In addition, his performance is normal in an immediate and delayed recognition memory for faces, whose external features were deleted. His deficits in face recognition are apparent only when he is required to name a famous face, or select two faces from among a triad of famous figures based on their semantic relationships (a task which does not require access to names). The nature of his deficits in object perception and recognition are similar to his impairments in the face domain. This pattern of behavior supports the notion that apperceptive and associative agnosia reflect distinct and dissociated deficits, which result from damage to different stages of the face and object recognition process. ... Read more

Book Description
This book has been created for patients who have decided to make education and research an integral part of the treatment process. Although it also gives information useful to doctors, caregivers and other health professionals, it tells patients where and how to look for information covering virtually all topics related to agnosia (also Agnosis Primary; Monomodal Visual Amnesia; Visual Amnesia), from the essentials to the most advanced areas of research. The title of this book includes the word official. This reflects the fact that the sourcebook draws from public, academic, government, and peer-reviewed research. Selected readings from various agencies are reproduced to give you some of the latest official information available to date on agnosia. Given patients' increasing sophistication in using the Internet, abundant references to reliable Internet-based resources are provided throughout this sourcebook. Where possible, guidance is provided on how to obtain free-of-charge, primary research results as well as more detailed information via the Internet. E-book and electronic versions of this sourcebook are fully interactive with each of the Internet sites mentioned (clicking on a hyperlink automatically opens your browser to the site indicated). Hard-copy users of this sourcebook can type cited Web addresses directly into their browsers to obtain access to the corresponding sites. In addition to extensive references accessible via the Internet, chapters include glossaries of technical or uncommon terms. ... Read more

Book Description
This digital document is a journal article from Neuropsychologia, published by Elsevier in . The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

Description:
Patients with colour agnosia can perceive colours and are able to match coloured patches on hue, but are unable to identify or categorise colours. It is a rare condition and there is as yet no agreement on the clinical definition or a generally accepted explanation. In line with observations from object agnosia and prosopagnosia, we hypothesised that (some of) these patients might still be able to process colour information at an implicit level. In this study, we investigated this possibility of implicit access to colour semantics and colour names in a man (MAH) who suffers from developmental colour agnosia. We designed two experimental computer tasks: an associative colour priming task with a lexical decision response and a reversed Stroop task. The results of these experiments suggest that there is indeed automatic processing of colour, although MAH was unable to explicitly use colour information. ... Read more

Book Description
This digital document is a journal article from Neuropsychologia, published by Elsevier in 2005. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

Description:
Dissociation between the ability to recognize misoriented objects and to determine their orientation has been reported in a small number of patients, but the long-term course of this deficit has not been reported so far. Here, we describe the case of a 32-year-old female who had bilateral occipito-temporal damage caused by a cerebrovascular accident. Neuropsychological assessment performed at 6 months after the occurrence of the cerebrovascular accident revealed that she was almost generally agnostic for object orientation. The patient was then re-tested 3 years later, when she showed apparently striking recovery in her ability to determine object orientation. However, closer examination revealed that she still displayed the same impairment, although at this time, it was only for objects presented in non-cardinal angles. Moreover, she had problems mostly discriminating orientations that differed by small amounts. The ability of patients to discriminate a variety of orientations should be further tested in future investigations in this field. ... Read more

Book Description
This digital document is a journal article from Cognitive Brain Research, published by Elsevier in 2004. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

Description:
We tested a patient with visual agnosia who had suffered severe bilateral brain damage early in life, on a series of visuomotor tasks. The broad pattern of results confirms that S.B., like the extensively tested patient D.F., shows an impressive array of preserved skills, despite his severe perceptual problems. Also like D.F., S.B. shows certain subtle visuomotor difficulties that can be related to the idea that his partially intact occipito-parietal areas are unable to benefit from interactions with the apparently severely damaged occipito-temporal regions. Unlike D.F., however, he is able to make accurate discriminations of simple visual features, such as object width and orientation, albeit with very slow response times. We hypothesize that several factors such as the early onset of S.B.'s lesion and the long period since his brain lesion have allowed his brain to compensate to a degree what has been impossible in D.F., whose brain damage occurred in adulthood. This may include an element of 'rewiring' and self-monitoring of visuomotor processes that allow S.B. to achieve perceptual access to visual information processed in the dorsal stream: information that is normally only available for on-line visuomotor control. ... Read more

Book Description
This digital document is a journal article from Neuropsychologia, published by Elsevier in 2007. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

Description:
An important aspect of research into the link between genes and behaviour concerns the identification of familial determination. There is evidence for familial factors in selective deficits, such as developmental dyslexia and developmental prosopagnosia. Colour agnosia concerns a selective neuropsychological condition in which colour perception is intact, while the identification and naming of colour is disrupted. We recently demonstrated that this deficit can occur as a developmental deficit. Here, we show that there is a familial factor in the development of colour agnosia by reporting the colour processing abilities of the mother and the daughters of a man with developmental colour agnosia. ... Read more

Book Description

Targeted to patients, their families and allied health students, The Gale Encyclopedia of Neurological Disorders provides in-depth coverage of neurological diseases and disorders, including stroke, multiple sclerosis, Parkinson disease, Tourette Syndrome, Alzheimer's disease, cerebral palsy, vertigo, amnesia and epilepsy. Related topics include communication aids, electric personal assistive mobility devices, medications for treating neurological diseases and conditions, understanding the needs of Alzheimer patient caregivers and more. This two-volume set provides an alternative to resources that either fail to explore neurological disease in any depth and or do so at a level not appropriate for students and general readers.