Grammatical ClassSpecific Anomias

The early grammatical-class dissociation observed in the anomias was that between content-laden ("substantive") words and functors, those "small words" like "if," "is," and "who" that convey primarily syntactic information. Patients with a type of aphasia called agrammatism, of course, produce predominantly substantives and few functors. However, agram-matism itself traditionally has not been considered primarily an anomic problem. Rather, problems with retrieving substantives (nouns, verbs, adjectives, and, perhaps, adverbs) in running speech or on confrontation naming constitute anomia.

Like the category-specific anomias, grammatical-class dissociations in naming have been reported that include noun-verb dissociations and proper-name-retrieval failures. Unlike semantic-category dissociations, however, noun-verb retrieval dissociations are more tightly coupled with particular lesion territories. That is, individuals with selective impairment of object naming have left posterior language-zone lesions of the temporal cortex, whereas individuals with selective impairment of action naming have left anterior language-zone lesions of the frontal cortex. The controversy in the domain of noun-verb naming dissociations lies in what these lesions represent in terms of the language system. If the anterior area is associated with verb problems and the posterior area is associated with noun problems, how can we account for the category-specific problems discussed earlier? One possibility is that they arise from smaller lesions than the one that results in general problems with nouns. A second possible explanation is that both the representations for semantics and phonology remain intact for nouns as well as for other substantives but that there is a disconnection between specific semantic centers and the store of the phonological shapes of names. In addition, this second theory assumes that the distribution of semantic and phonological representations for nouns is separate from that for verbs, nouns being distributed throughout the temporal lobe and verbs being distributed throughout the frontal lobe.

In addition to noun-verb dissociations, evidence for specific deficits in proper-name retrieval has been reported primarily by Semenza and colleagues. Le sions of the left temporal pole are associated with this deficit. In individuals with proper-name impairments, common nouns are largely preserved. Even names that would have been well-known before the aphasia are markedly more difficult to access. Indeed, some patients have been reported to have a dissociation between their ability to retrieve proper names for people and that for geographic locations and landmarks. The explanation offered for such dissociations has been that proper names, especially those for people, have limited associations to other items in the lexicon. For example, the occupation baker has associations to other occupations and to what bakers do and produce, whereas the last name Baker refers more arbitrarily to the individual or family one happens to know with that last name. For geographical locations and landmarks, the name may be associated more strongly with other information about that place, for example, one may associate the Eiffel Tower with everything one knows about Paris and France.

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