The Japanese journal of neuropsychology

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ArticleTitle	Semantic dementia
Language	J
AuthorList	Mamoru Hashimoto
Affiliation	Department of Neuropsychiatry, Kumamoto University Hospital
Publication	Japanese Journal of Neuropsychology: 26 (4), 283-293, 2010
Received
Accepted
Abstract	Semantic dementia is a clinical syndrome characterized by selective degradation of semantic knowledge due to circumscribed, bilateral atrophy of the anterior temporal lobes. This semantic memory loss can be detected even in early-stage SD. Research on SD suggests that although separate and widespread brain regions represent individual domains of knowledge about an object, the bilateral anterior temporal lobes play a key part in linking and coordinating this information, in enabling a various of conceptual knowledge about an object to be retrieved on the basis of receiving a part of information about it in a single modality, and in enabling generalization across similar concepts. The most striking feature of cognitive attitude in SD under the conditions of a degraded semantic system is over- and undergeneralization. Overgeneralization is the error influenced by information that is general to many items rather than specific to a given concept. On the other hand, undergeneralization is the error influenced by the concept whose boundaries are severely reduced. This phenomenon is observed through verbal and nonverbal tasks and everyday behaviors and suggests that SD may be characterized by impaired semantic generalization.
Keywords	semantic dementia, semantic memory, anterior temporal lobe, conceptulization