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Poster E72, Friday, November 10, 10:00 – 11:15 am, Harborview and Loch Raven Ballrooms

Sensitivity to phonetic competition in People with Aphasia

Kathrin Rothermich1, David Saltzman1, Xin Xie2, Emily Myers1,3;1University of Connecticut, 2University of Rochester, 3Haskins Laboratories

Speech perception deficits are common across different types of aphasia, and neurobiological models of language have indicated that deficits concerning mapping the speech signal to meaning occur mainly following lesions in the temporal lobes (Hickok and Poeppel, 2004, 2007). However, other lesion studies have shown that damage to left frontal brain areas can lead to impairments in certain speech perception tasks, especially when stimulus materials involve phonetic competition (i.e., between similar speech sounds; Utman et al., 2001; Misiurski et al., 2005). Recent fMRI studies confirm this view by showing that the left inferior frontal gyrus (LIFG) is activated when resolving phonetic competition (Myers, 2007; Myers & Blumstein, 2008; Xie & Myers, submitted), while the left temporal lobe responds to less phonetically competitive speech (Myers, 2007). Our main goal in this study is to shed light on the division of labor between temporal and frontal areas during speech processing, specifically investigating the hypothesis that frontal regions play a key role in resolving lexical competition when the signal is phonetically more ambiguous. The current study examines the effect of aphasia following left-hemispheric lesions on the performance of resolving phonetic competition in connected speech in a naturalistic task. Fluent and non-fluent people with aphasia (PWA, N=10) as well as undergraduate students (N=13) listened to nonsensical sentences and indicated whether a target word was part of a sentence or not. Importantly, the natural variation of phonetic competition in these sentences was manipulated by exploiting variation in speech register, where conversational speech tends to have more phonetic competition and clear (i.e., hyperarticulated) speech minimizes phonetic competition. PWA were between 53-72 years of age and with chronic aphasia and a mix of aphasia types (anomic, Broca’s, and conduction aphasia). Severity was assessed via the Boston Diagnostic Aphasia Examination (BDAE) battery and as well as using subtests taken from the Psycholinguistic Assessments of Language Processing in Aphasia (PALPA). Brain lesions were identified from high-resolution T1-weighted MRI scans using manual lesion mapping in MRIcron as well as by a semi-automated procedure (Lesion Identification with Neighborhood Data Analysis; Pustina et al., 2016). In typical undergraduates, we observe a significant advantage for clear speech in terms of percent accuracy (casual: 88 %; clear: 92 %), but no effect for reaction time (RT). In PWA, we see overall lower accuracy and no consistent advantage for clear speech (casual: 68 %; clear: 70 %), which seems to depend on severity. Perhaps surprisingly, PWA profit less from clear speech, which may stem from an inability to integrate fine-grained phonetic information with lexical content. To understand the exact contribution of frontal and/or temporal areas, Voxel Lesion Symptom Mapping approaches will be used further assess the relationship between specific lesion sites and task performance.

Topic Area: Perception: Speech Perception and Audiovisual Integration

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