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Behavioral and neural measures of error detection and correction in persons with aphasia

Caroline A. Niziolek1* and Swathi Kiran1
  • 1 Boston University, Department of Speech, Language, and Hearing Sciences, United States

Background: Speech production errors, including phonemic paraphasias, are a hallmark of aphasic speech. Because speech production deficits in aphasia are often accompanied by abnormalities in perception (Blumstein, 1994) and in feedback processing (Boller & Marcie, 1978; Boller, Vrtunski, Kim, & Mack, 1978; Chapin, Blumstein, Meissner, & Boller, 1981), these deficits have been hypothesized to stem from problems with auditory-motor integration (Buchsbaum et al., 2011; Hickok & Poeppel, 2004) and encoding auditory feedback (Oomen, Postma, & Kolk, 2005). This project investigates the functional source of speech errors in aphasia by assessing the extent to which persons with aphasia (PWA) use feedback to detect and correct deviations in their speech. Past research in healthy control speakers shows that the brain is sensitive to small deviations in auditory feedback, and that this sensitivity is related to a corrective movement that reduces the deviation, bringing utterances back on target (Niziolek, Nagarajan, & Houde, 2013). We hypothesize that this feedback detection-correction circuit may be impaired in some PWA, resulting in a higher frequency of speech errors. Methods: Eight persons with aphasia took part in a two-phase experiment aimed at assessing error detection and correction abilities. The participants were between 50-73 years of age (mean: 56.6; SD: 7.7), had chronic aphasia (months post-stroke: mean = 68.6; SD = 28.3), and were assessed using the Western Aphasia Battery (WAB-R) and repetition subtests from the Psycholinguistic Assessments of Language Processing in Aphasia (PALPA). Phase 1 examined the ability of PWA to correct their speech online. The eight participants completed a behavioral experiment in which they produced 200 repetitions each of three monosyllabic words (“eat”, “Ed”, “add”). First and second formant (F1 and F2) trajectories for each vowel were calculated and compared across productions for a measure of variability at the onset and midpoint of the syllable (Niziolek et al., 2013). Vowel centering was defined as formant movement toward the median, lessening variability over the time course of the syllable (Fig. 1A). Results: In the majority of aphasic speakers, acoustic variability significantly decreased over the course of the syllable. However, compared with healthy controls (Fig. 1A), PWA show much more variability at onset (Fig 1B). Furthermore, as in controls, the degree of formant correction in PWA was correlated with initial acoustic variability (r = 0.502; p = 0.028), but for PWA the percent correction falls off for the most highly variable individuals (Fig. 1C). Conclusions: PWA exhibit vowel centering, suggesting that during correct syllable production, online feedback correction mechanisms are at work. However, given higher variability and smaller relative correction, it is unclear whether the same neural mechanisms underlie this correction in PWA and healthy speakers. In phase 2, we use magnetoencephalographic (MEG) imaging to analyze auditory error detection ability in PWA during the production of the same syllables from phase 1, treating auditory cortical suppression as a measure of sensitivity to self-produced acoustic deviations. These complementary analyses will inform theories of error detection and correction in healthy speakers and models of error prevalence in persons with aphasia.

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References

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Keywords: Aphasia, speech errors, auditory feedback, Vowel acoustics, MEG

Conference: 54th Annual Academy of Aphasia Meeting, Llandudno, United Kingdom, 16 Oct - 18 Oct, 2016.

Presentation Type: Platform Sessions

Topic: Academy of Aphasia

Citation: Niziolek CA and Kiran S (2016). Behavioral and neural measures of error detection and correction in persons with aphasia. Front. Psychol. Conference Abstract: 54th Annual Academy of Aphasia Meeting. doi: 10.3389/conf.fpsyg.2016.68.00124

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Received: 01 May 2016; Published Online: 15 Aug 2016.

* Correspondence: PhD. Caroline A Niziolek, Boston University, Department of Speech, Language, and Hearing Sciences, Boston, MA, United States, cniziolek@wisc.edu