Examining inhibition during spoken word production in aphasia
Pompon, Rebecca Hunting
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The nature of selective attention in people with aphasia (PWA) is currently unknown. Selective attention, or our ability to focus on relevant information and ignore distractions, is essential for everyday communication. Inhibition, or suppression of unwanted information, is an important part of selective attention. This study explored components of inhibition in spoken word production in aphasia, a language disorder impacting more than a million people across the U.S. Specifically, this study examined both interference effects and subsequent reactive inhibition, or the carryover suppression of a previous distraction. Nineteen PWA and 20 age- and education-matched controls participated in a spoken word production task involving Stroop and negative priming experimental paradigms. Stroop color-word stimuli were used to evoke interference and facilitation effects as baseline conditions. Stroop stimuli were also used in negative priming prime-probe pairs, where the prime distractor becomes the probe target, a method of testing reactive inhibition. Response latency and accuracy data were recorded for participants. Research questions were addressed by group-by-condition interactions, analyzed via repeated measures ANOVA and nonparametric/Mann-Whitney tests. Results showed that while both groups demonstrated interference effects, the effects were significantly greater for PWA, as reported in previous research. Interestingly, PWA demonstrated no significant facilitation effects; Controls demonstrated significant reverse facilitation effects. This result was interpreted as PWA's inability to take advantage of contextual cues of proportion. Neither group showed statistically significant evidence of inhibitory rebound, though both groups showed surprisingly similar individual variability, suggesting inhibitory rebound for some and repeated interference facilitation for others. Lastly, PWA demonstrated a near-significant response slowing when a congruent probe had just served as prime distractor, potentially indicating diminished conflict adaptation. These results underscore the challenges interference presents for PWA during spoken word production and indicates potentially diminished executive inhibition. However, PWA's automatic/reactive inhibition appears equivalent to controls, and therefore not a contributing factor in word retrieval impairments of aphasia. However, PWA may have difficulty adapting to contextual information compared to their neurologically healthy counterparts. These results provide direction for future research of selective attention in aphasia -- aimed to improve clinical protocols for people with this language impairment.
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