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Article Excerpt
Patterns of word retrieval failure, in the form of episodes (number of consecutive errors), were investigated in fluent and nonfluent aphasic adults with word retrieval problems. Specifically, the occurrence of one, two, three, and four-plus consecutive word retrieval errors on the Test of Adolescent/Adult Word Finding (TAWF) were analyzed. The results revealed three distinct patterns of word retrieval failure, identified as fleeting, clustered, and extended. The fluent aphasic adults demonstrated primarily a fleeting pattern of word retrieval failure, whereas most of the nonfluent aphasic adults displayed more extended episodes of word retrieval failure. However, severity of word retrieval deficit, as determined by standard score on the TAWF, did not necessarily predict the retrieval failure pattern that was displayed. The results are discussed relative to verbal output fluency in aphasia and interactive activation models of language production.
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Most aphasic adults have been found to have difficulty with word finding (Davis, 1993, 2000; Good-glass, 1993; Nickels, 2001; Rosenbek, LaPointe, & Wertz, 1989). These deficits have been studied extensively, examining the effect of such variables as task context, task difficulty, stimuli utilized, retrieval strategies, and the patient's lexical response with emphasis primarily on type of error (Goodglass & Stuss, 1979; Hough, 2006; Kohn & Goodglass, 1985; Laine, Kujala, Niemi, & Uusipaikka, 1992; Mitchum, Ritgert, Sandson, & Berndt, 1990; Nickels, 2001). Furthermore, one task that has been found to consistently reveal a word finding deficit in aphasia is naming (Davis, 2000; Goodglass & Kaplan, 2001; Nickels, 2001). In this type of task, the individual is required to provide lexical information in the form of the word name when presented with conceptual information, such as the definition of a word, sentence completion frame, or confrontation naming when the person is presented with a picture of an object and/or action (Humphreys, Price, & Riddoch, 1999; Humphreys, Riddoch, & Quillian, 1988; Martin, Weisberg, & Saffran, 1989). The stimulus (picture, sentence completion, or definition) is thought to directly activate its semantic representation at the semantic network level and then indirectly activate the word name at the lexical level (Carr, McCauley, Sperber, & Parmalee, 1982; Humphreys et al., 1999; Riddoch, Humphreys, Coltheart, & Funnell, 1998).
In the current investigation, episodes of word retrieval failures were examined in a group of aphasic adults, incorporating Stemberger's (1985, in press) Interactive Activation Model and Burke, MacKay, Worthley, and Wade's (1991; Burke, MacKay, & James, 2000; Rastle & Burke, 1996) Node Structure Theory to explain the distinct word retrieval patterns observed in subgroups of these individuals. In these models, the language system is depicted as a network of hierarchically organized and interconnected nodes (units) that are comprised of the semantic, phonological, and motor programming systems. The semantic system is hierarchically organized into propositional nodes that are broken down into lexical nodes that contain no phonological information. This system, however, connects to the phonological system that is hierarchically organized into syllable, consonant cluster, vowel, single consonant, and phonological feature nodes. Phonological system nodes connect to the motor programming system. Nodes appear to be activated in an all or none fashion. An activated node will prime or provide some subthreshold excitation to all nodes connected to it. Priming spreads in parallel to all connected nodes at both higher and lower levels. During normal error-free word finding, activation of propositional nodes representing a concept occurs initially, with this activation priming the lexical nodes that, in turn, prime the phonological nodes. The lexical node for an intended word is activated if it receives more priming than some other node. This processing operation is referred to as priming summation. The word receiving the greatest amount of activation appears to inhibit other words. The framework presented in both models has been supported by Dell, Chang, and Griffin (1999) in their interactive activation approach to lexical access in production and...
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