The Crucial Role of Lexical Content in Nonfluent Aphasic Sentence Production
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1
Victoria University of Wellington, New Zealand
Background: Individuals with nonfluent aphasia may have great difficulty producing sentences, even despite being able to produce many words accurately in isolation. This disorder could therefore provide important insights into the cognitive processes involved in sentence production. Most research to date has compared accuracy across different types of sentence structures, while only paying little attention to lexical content. However, if lexical items activate their associated grammatical frames as well as vice-versa, then rapid access to lexical items – particularly ones appearing early in the sentence - may also be vital, especially if the sentence plan is weak or rapidly decaying. Furthermore, previous research suggests that utterances containing meaning related words may be challenging for individuals with nonfluent aphasia, possibly because lexical representations are inadequately tied to an appropriate structural representation. The current study investigates the effect of lexical content on sentence production in nonfluent aphasia.
Methods: Five participants with nonfluent aphasia, four with fluent aphasia and eight healthy controls described pictured events that were extensively normed to elicited SVO sentences (e.g., The dog is chasing the fox). These were interspersed with filler pictures requiring different structures. Based on the premise that frequent words are accessed more rapidly than rarer ones, Experiment 1 manipulated the frequency of the subject and object nouns in. In Experiment 2, we examined the semantic relationship between subject and object nouns.
Results: In Experiment 1, sentence accuracy was consistently higher on sentences commencing with a high frequency subject noun for the nonfluent participants – but not for any of the fluent cases. This pattern remained unchanged when errors on the subject nouns themselves were excluded. In Experiment 2, the nonfluent participants produced sentences less accurately when they contained meaning related lexical items – the opposite pattern was observed for the fluent participants.
Discussion: These results demonstrate that lexical context has a powerful influence on sentence production success in nonfluent aphasia. We propose that individuals with nonfluent aphasia are disproportionately reliant on activated lexical representations to drive the sentence generation process, an idea we call the Content Drives Structure (COST) hypothesis.
Keywords:
Aphasia,
Nonfluent aphasia,
Broca’s aphasia,
sentence production,
lexical retrieval,
lexical competition
Conference:
ACNS-2013 Australasian Cognitive Neuroscience Society Conference, Clayton, Melbourne, Australia, 28 Nov - 1 Dec, 2013.
Presentation Type:
Oral
Topic:
Language
Citation:
Speer
P and
Wilshire
CE
(2013). The Crucial Role of Lexical Content in Nonfluent Aphasic Sentence Production.
Conference Abstract:
ACNS-2013 Australasian Cognitive Neuroscience Society Conference.
doi: 10.3389/conf.fnhum.2013.212.00148
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Received:
15 Oct 2013;
Published Online:
25 Nov 2013.
*
Correspondence:
Ms. Paula Speer, Victoria University of Wellington, Wellington, New Zealand, paula.speer@vuw.ac.nz