The long-term objective of this project is to characterize the cognitive/linguistic mechanisms that are implicated in various forms of morphological processing impairment.
AIMS 1) to differentiate the respective contributions of deficit to specifically morphological processing mechanisms from deficits to lexical, phonological, syntactic, or other cognitive/linguistic processes involved in language use; 2) to characterize in detail the internal structure of the lexical system that recognizes, stores, constructs and interprets morphologically complex words in either auditory or visual modalities, thereby providing the basis for a deeper understanding of the morphological processing deficits presented by brain-damaged patients. This program or research has a two part structure. In the first part,k relatively large numbers of English, Italian and French aphasic patients with focal brain lesions who make morphological errors in speaking, reading, or writing are administered an extensive battery of tasks that are a) designed to identify the locus of impairment with respect to syntactic vs lexical impairments, and b) to define subgroups of patients--in the cases of lexical impairment--based on the particular components of the lexical system that are implicated. Patients' performance will be used to refine the testing materials of the Morphology Battery so as to better discriminate among different types of impairment and to evaluate specific hypotheses about the internal structure of particular components of morpho-lexical processing. The second part consists of highly detailed analyses of individual patients who present with selective deficits at different levels of the lexical system. A major new aspect of the proposed research motivated by findings of the first grant period is a shift toward much greater emphasis on morpho-phonological aspects of word processing. Among the specific issues that we propose to address in this regard are the relationship between morphological and phonological processes in word production; and the functional connection between phonological and morphological deficits. A further component of the proposed research is experiments with normal subjects designed to address issues of morphological processing and representation in order to extend and illuminate our findings with acquired language impairments. Finally the detailed characterization of morphological processing abilities will be used to explore correlations between locus of brain damage and type of functional disorder. The results of the proposed studies will contribute to a deeper understanding of the patterns of morphological deficits that may result from brain damage, the importance of which is to furnish an essential foundation for the diagnosis and remediation of these acquired language impairments.