Poster D81, Wednesday, August 21, 2019, 5:15 – 7:00 pm, Restaurant Hall
An electrophysiological marker of unexpected interruptions of natural speech flow.
Irina Anurova1, Aleksandra Dobrego2, Alena Konina2, Nina Mikusova2, Nitin Williams1, Anna Mauranen2, Satu Palva1;1University of Helsinki, Neuroscience Center, 2University of Helsinki, Department of Languages
As suggested by a theoretical model of Linear Unit Grammar (Sinclair & Mauranen 2006), efficient comprehension of continuous speech assumes segmentation of speech flow into manageable chunks. Furthermore, it has recently been shown that people’s choices regarding the locations of boundaries separating two consecutive chunks tend to converge with high probability (Vetchinnikova & Mauranen 2017). In the present study, we recorded brain activity during two contrasting types of pauses, ‘natural’ and ‘unnatural’, inserted into auditory speech stimuli in order to test whether unexpected interruption of speech flow affects natural speech processing. We conducted simultaneous EEG–MEG recordings in 21 healthy volunteers during the performance of a comprehension task. In a forced-choice paradigm (yes/no), the participants had to answer a comprehension question presented after each auditory speech stimulus. The stimuli were 10-45-second extracts selected from natural speech events from a corpus of academic English, and reproduced by a trained speaker, who mimicked the original intonation patterns with high precision. We inserted 2-second silent gaps into the stimuli at predictable locations (natural boundaries) separating successive chunks, and at unpredictable locations (unnatural boundaries). Selection of natural boundaries was based on the results of a prior behavioral experiment conducted in a separate group of 53 subjects. A half of selected natural boundaries was marked in the behavioral experiment with high probability (by more than 75% of participants), and a half – with medium probability (around 50%). Unnatural boundaries were selected at the locations where the probability of boundary markings did not exceed 5%. We found that unexpected interruption of speech flow elicited both electric and magnetic counterparts of the emitted potential, a prominent negative peak with a latency of around 200 ms. The emitted potential was not observed during natural boundaries behaviorally marked either with medium or high probability. The present results suggest that the emitted potential may be considered as a reliable marker of unexpected interruptions during natural speech flow.
Themes: Speech Perception, Perception: Auditory
Method: Electrophysiology (MEG/EEG/ECOG)