Poster D86, Wednesday, August 21, 2019, 5:15 – 7:00 pm, Restaurant Hall
Investigating the neural bases of self-monitoring of speech in people with aphasia: an ERP study
Heather Ouellette1, Francesco Usai1, Aaron, J. Newman1;1Dalhousie University
Aphasia often impairs the ability to detect errors in incoming speech, limiting the effectiveness of communication and the chances to benefit from treatment. While self-monitoring of speech production is important in aphasia recovery, its cognitive and neural underpinnings are not well understood, either in healthy people and older adults with stroke. A better understanding of such processes would benefit the design of treatment aiming to remediate this deficit. In healthy people error detection has been associated to activity in the mid-prefrontal cortex (PFC), as typically indexed by the error-related negativity (ERN) - an event-related potential (ERP) component that is sensitive to response accuracy. It is not clear whether in people with aphasia—who typically have higher error rates and low detection rates—the relationship between the ERN and self-monitoring abilities is consistent with what is observed in healthy subjects. To address this question, we conducted an ERP study to assess whether the presence, or lack thereof, of the ERN was contingent on participants' ability to detect their mistakes. Five people with aphasia (2 females) participated in this study (with recruitment ongoing). We recorded EEG while participants performed a picture-naming task, and observed the effect of response accuracy on the ERN. To do that, the time courses and scalp topographies of ERPs (locked to voice-onset time) were contrasted for correct and incorrect responses. Vocal responses were recorded and later categorized based on naming accuracy, wherein errors were considered as any type of paraphasia and hesitations, even when subjects corrected an initially erroneous response. To gauge self-monitoring abilities, participants were prompted to signal whether they thought they made a mistake by button pressing. In addition, we analyzed vocal responses categorized as erroneous, distinguishing those showing evidence of error-detection (i.e correcting, or rejecting a response) from others. ERP responses - defined as the mean amplitude of the ERP in the time window from 0 to 300 ms after response-onset - were analysed using linear mixed effects models, with channel location and response accuracy as fixed effects (expressed as an interaction between the two terms). Analysis of behavioral responses showed that people with anomia (n=3) made the least amount of errors, both in absolute and relative terms, compared to the other two participants. Participants also showed little awareness of their mistakes, with detection rates lower than 20%, except for one participant who detected 17/36 errors. Statistical analysis showed no effect of response accuracy on ERP amplitude, suggesting that the ERN was not elicited by speech errors in this group, and more generally that the neural responses associated with correct and incorrect naming were not distinguishable. The poor self-monitoring abilities of people with aphasia and the absence of the ERN component observed in the data acquired to date confirm prior reports of poor self-monitoring in aphasia, but provide insufficient evidence to draw conclusions about the role of the ERN in this population. We are currently recruiting people with more severe aphasia and increasing task difficulty in an effort to increase error rates.
Themes: Speech Perception, Disorders: Acquired
Method: Electrophysiology (MEG/EEG/ECOG)