| Summary: | abstract: Working memory (WM) and attention deficits have been well documented in individuals with aphasia (IWA) (e.g. Caspari et al., 1998; Erickson et al., 1996; Tseng et al., 1993; Wright et al., 2003). Research into these cognitive domains has spurred a theoretical shift in how aphasia is conceptualized - from a purely linguistic disorder to a cognitive-information processing account. Language deficits experienced by IWA may result from WM impairments or from an inability to allocate cognitive effort to the tasks. However, how language impacts performance on these tasks has not been readily investigated. Further, there is a need for a more direct measure of effort invested to language tasks. Heart rate variability (HRV) is a physiological measure of cognitive workload that has been used to measure effort in neurologically intact participants. Objectives of the study included: (1) determining the feasibility of using HRV as a measure of effort IWA invest into verbal compared with spatial WM tasks, (2) Comparing participants' performance on verbal and spatial WM tasks; and (3) determining the relationship among performance, perceived task difficulty, and HRV across verbal and spatial tasks. Eleven IWA and 21 age- and education-matched controls completed verbal and spatial n-back tasks at three difficulty levels. Difficulty ratings were obtained before and after each task. Results indicated spatial WM was relatively preserved compared with verbal WM for the aphasia group. Additionally, the aphasia group was better at rating task difficulty after completing the tasks than they were at estimating task difficulty prior to completing the tasks. Significant baseline-task differences in HRV were found for both groups. Relationships between HRV and performance, and HRV and task difficulty were non-significant. Results suggest WM performance deficits in aphasia may be primarily driven by their language deficit. Baseline-task differences in HRV indicate effort is being allocated to the tasks. Difficulty ratings indicate IWA may underestimate task demands for both verbal and spatial stimuli. However, the extent to which difficulty ratings reflect effort allocated remains unclear. Additional research is necessary to further quantify the amount of effort IWA allocate to verbal and non-verbal tasks. === Dissertation/Thesis === Ph.D. Speech and Hearing Science 2012
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