Semantic Knowledge Impairments

Of the many different characteristics and exclusionary criteria discussed in the previous chapters, there has so far been one constant whatever the impairment is, it is manifest only with visual stimuli. The ability to demonstrate knowledge about an object when probed verbally must be established before a failure with the object presented visually can be considered a visual agnosia. The word agnosia has also been applied to patients with an impairment of knowledge that is not limited to visual...

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Normal subjects' errors Normal subjects' errors Naming accuracy of normal subjects with tachistoscopicaHy presented pictures, as a function of the naming accuracy of two patients with selective semantic memory impairments for living things. aphasic that detailed investigation was impossible. Hillis and Caramazza (1991) described two patients with selective impairments of semantic knowledge, one ofwhom showed a striking preservation of animal-related knowledge. They report that his naming of...

Associative Visual Agnosia

Like the term apperceptive agnosia, associative agnosia has been used quite broadly to cover a heterogeneous set of conditions. It includes impairments in general semantic knowledge and impairments confined to the naming (as opposed to the recognition) of visually presented objects, which are discussed in chapters 8 and 9. The more common and specific meaning ofassociative agnosia is a selective impairment in the recognition of visually presented objects, despite apparently adequate visual...

Prosopagnosia and Topographic Agnosia

7.1 Modules and Special Systems As cognitive science emerged from the fields of psychology, computer science, and linguistics in the 1970s, it defined its main scientific business as characterizing the functional architecture of cognition (e.g., Pylyshyn, 1981). Architecture conveyed its emphasis on the large-scale structure of the cognitive system and was suggestive of a structure with clearly demarcated components. A general issue that arose in this context was how extensively parcelated the...

Perceptual Categorization Deficit and Disorders of Orientation Processing

Simultagnosia

The patients in the foregoing chapters have clinically evident problems, and much of what is known about them comes from clinical case descriptions. There are other patients who have been termed visual agnosic but whose disorders rarely cause them problems in everyday life. These types of agnosia are demonstrated in experimental tasks, and may be studied in groups of patients delineated by lesion site as well as in individual cases selected for their poor performance on the relevant tests. In...