.) The intent of the proposed research is to relate aphasic patients' reduced memory spans to single word processing, to sentence comprehension and production, and to long-term learning. A basic assumption of this research is that there are separable phonological and lexical- semantic contributions to memory span that may be independently disrupted in different patients.Patients' performance on word perception, lexical comprehension and word production will be evaluated to determine the extent to which there is a correspondence or dissociation between phonological and semantic abilities in word processing and phonological and semantic retention capacities. One issue to be addressed is whether there are separable input and output phonological STM capacities that relate to patients' speech perception and production abilities. At the level of sentence processing, the proposed research will investigate whether the lexical-semantic retention capacity that appears to be involved in sentence comprehension also plays an important role in speech production. Although phonological STM does not appear to be critical to sentence comprehension, it is possible that this capacity is involved in speech planning at the phonological level. With regard to long-term learning, the proposed studies will investigate whether deficits in the short-term retention at the phonological and lexical-semantic levels lead to impaired long-term learning deficits for phonological and lexical-semantic information. A modified case study approach will be used, in that a relatively small number of patients will be tested on a large number of tasks. The advantage of the case study approach is that dissociations that might be present in a few cases (e.g., good syntactic comprehension together with reduced memory span) might be masked in group data. The approach differs from typical case studies, however, in that a number of patients will be tested on the same tasks. In this fashion it should be possible to determine whether deficits that appear to be associated in some cases are necessarily associated in all cases.
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