Dissertation Defense: Mackenzie Fama
Candidate Name: Mackenzie Fama
Advisors: Peter E. Turkeltaub, M.D., Ph.D. and Rhonda B. Friedman, Ph.D.
Title: The Subjective Experience of Inner Speech in Aphasia
All individuals with aphasia experience some level of anomia, or difficulty with naming and word finding, but many report that their internal word knowledge exceeds their spoken output, making comments like, “I know it but I can’t say it” or even more specifically, “I can say it in my head” (but not aloud). Such comments align with processing models of naming, which include multiple stages of lexical retrieval and post-lexical output processing. Given that anomia can arise from impairments at any one (or more) of the processing stages, it is conceivable that feelings of intact lexical knowledge reported by people with aphasia reflect success in the early stages, despite overt anomia resulting from impairment at a later stage.
In this dissertation, I examine the specific experience of “inner speech” (IS), defined in this context as a sense of being able to say a word in one’s head, regardless of subsequent ability to say that word aloud. Our hypotheses are that (1) the subjective experience of IS in aphasia reflects the status of lexical (phonological) retrieval and (2) IS itself does not rely on post-lexical stages of naming, so a failure of naming following successful IS results from deficits at the level of post-lexical output processing. Two approaches are used to elicit self-reports of IS from individuals with aphasia: an interview-based approach regarding the general experience of IS and an item-by- item approach in the context of silent naming. Self-reported IS is then compared to structural brain imaging and objective language measures related to the mental processes of naming (e.g., tasks emphasizing retrieval vs. output, error patterns, and psycholinguistic properties of words). The results of these studies consistently support the hypotheses, showing that self-reported IS relates to measures of phonological retrieval but not articulatory processing.
Overall, the findings of these studies support a theory in which the experience of IS arises in conjunction with lexical retrieval and articulatory processing is not essential to IS. This work has potential implications for clinical decision-making in the treatment of anomia as well as for our general scientific understanding of the nature of IS.
Monday, May 14, 2018 at 1:30pm to 3:30pm
Medical and Dental Building, SW 107
3900 Reservoir Road, N.W., Washington