Browsing by Author "Zahn, Rachel"

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    Language Production and Working Memory Abilities in Healthy Younger and Older Adults
    (2024-04-16) Zahn, Rachel; Martin, Randi
    Evidence from neuropsychological studies of individuals with brain damage post-stroke has supported the separation of working memory (WM) capacities for semantic (word meaning) and phonological (speech sound) information. These separate capacities have been shown to play different roles in supporting multiword language production, with semantic WM being particularly critical for the fluent production of multiword speech. The current study investigated the role that age-related declines in phonological and semantic WM play in language production. Using spontaneous production tasks and eye tracking during constrained sentence production, I investigated the characteristics of healthy young and older adults’ speech and speech planning processes and their relation to WM. These two methods provided converging evidence for the role of semantic WM in planning multiple content words during language production. In older adults’ narrative production, higher semantic WM capacity was associated with more elaborative speech. In sentence production with eye tracking, young adults with greater semantic WM capacity showed a greater tendency to look to a second noun in an initial phrase before speech onset, suggesting that they were planning both nouns before speaking and that this planning required semantic WM. The fact that older adults showed semantic WM effects in narrative production and young adults only showed effects in the eye gaze data highlights the advantage of combining eye gaze data with more standard behavioral measures in investigating the cognitive processes occurring before speech onset.
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    The Role of Phonological Working Memory in Narrative Production: Evidence from Chronic Aphasia
    (2021-05-10) Zahn, Rachel; Martin, Randi
    Previous work has supported a critical role for semantic, but not phonological, working memory (WM) in the ability to produce multiword utterances. In narrative production of patients at the acute stage of stroke it was shown that correlations between semantic, but not phonological WM, and narrative measures of elaboration remained when single word production abilities were included in the model. However, the acute stroke results also revealed relations between phonological WM and narrative production – specifically, a positive relationship between digit matching span (a phonological WM measure) and words per minute, and a negative relationship between digit matching span and proportion pronouns relative to nouns. Two hypotheses have been compared to explain these relationships. The first is that both digit matching span and these narrative measures relate to the speed and ease of phonological retrieval. The second is that there are separate input and output phonological WM buffers, and the output buffer plays a key role in fluent speech and phonological WM. In a sample of participants at the chronic stage of stroke two approaches, a case series and a case study approach, were used to address these two hypotheses. The case series approach showed evidence that single word retrieval abilities predicted words per minute above changes in output phonological WM, supporting the phonological retrieval hypothesis. However, the results for proportion pronouns differed between the acute and chronic stages, most likely due to different sources of variation in pronoun use for the two groups. The case series approach showed evidence for the distinction of input and output phonological WM buffers. Implications from the two approaches will be discussed.