Yulia Lamekina | Does Prosodic Entrainment Influence Segmentation? Towards a Predictive Account of Prosody

Yulia Lamekina (Max Planck Research Group Language Cycles), Burkhard Maess (Methods and Development Group Brain Networks), Lars Meyer (Max Planck Research Group Language Cycles)

Neural oscillations facilitate speech processing by synchronizing to rhythmic acoustic cues in speech. Delta-band oscillations (i.e., < 4 Hz) are thought to synchronize or entrain to speech prosody (for review, see Meyer, 2018). However, it is not clear whether such findings reflect oscillatory activity proper—or merely the frequency-domain equivalents of successive evoked responses (ERPs) that have been observed at the ending of prosodic units (for review, see Bögels et al., 2011).

Consistent with an oscillatory account, Steinhauer & Friederici (2001) found prosodic contours to prime the segmentation of a subsequent sentence that was stripped of prosody. This original effect could in fact mirror delta-band entrainment to prosody (Luo and Poeppel, 2007). Via entrainment, oscillations inherit a stimulation frequency to persist after stimulus offset, influencing the perception of upcoming stimuli (Kösem et al., 2018).

Because prosody indicates segmentation, we here investigated whether prosody entrainment can influence the segmentation of an upcoming sentence stripped of prosody. This would corroborate the hypothesis that the processing of prosody—and possibly syntactic segmentation—is supported by oscillatory activity. Moreover, it would entail a role of prosody in the temporal prediction of upcoming speech segments (cf. Stefanics et al., 2010). Our experiment combines initial prosody entrainment with the subsequent visual presentation of ambiguous sentences that allow for two different segmentation options and thus two alternative interpretations (Hoeks et al., 2002). Results from a behavioural pilot study support the hypothesis that entrainment affects downstream segmentation. We are next planning to assess the underlying electrophysiological dynamics with MEG. We expect to find delta-band phase differences depending on prosody entrainment at critical segmentation time points in the sentence, as well as power enhancement at stimulation frequency. For both prosody entrainment and the sentence, right posterior superior temporal gyrus / sulcus should be active (e.g. Alba-Ferrara et al., 2012, Ross and Monnot, 2008). During the visual sentence only (i.e., when the entrained oscillator continues without prosody), the right inferior frontal gyrus should be involved (cf. Wildgruber et al, 2006), consistent with a temporal prediction of the segmentation.