Prosodic Entrainment Influences Subsequent Sentence Comprehension
Yulia Lamekina1, Burkhard Maess2, Lars Meyer1,3; 1Max Planck Research Group Language Cycles, Max Planck Institute for Human Cognitive and Brain Sciences, 2Methods and Development Group Brain Networks, Max Planck Institute for Human Cognitive and Brain Sciences, 3Clinic for Phoniatrics and Pedaudiology, University Hospital Münster
Neural oscillations facilitate speech processing by synchronizing to rhythmic acoustic cues in speech. In particular, delta-band oscillations (< 4 Hertz) synchronize with speech prosody. In a series of behavioral studies, we have observed that rhythmic prosodic contours can trigger downstream effects that persist beyond stimulation, affecting the comprehension of upcoming sentences devoid of prosody. This is in line with the finding that via entrainment, oscillations can inherit a stimulation frequency to persist after stimulus offset. To support the interpretation that our behavioural effects reflect electrophysiological entrainment, we conducted an MEG experiment. We combined an initial prosodic rhythm with a subsequent visual target sentence. Target sentences were either long or short (e.g., “Max sees Tom and Karl laughs” vs. “Max sees Tom and Karl”). In a 2 × 2 design, these were combined with prosodic contours that were either long or short (corresponding to the durations of “Max sees Tom and Karl” and “Max sees Tom”, respectively). In the entrainment part of each experimental trial, a contour was repeated 3 times to induce rhythmic entrainment. In the target part, a visual target sentence was presented word by word; presentation was duration-matched to the rate of the previous stimulus. We first hypothesized that delta-band oscillations would entrain to the rate of the contours. Second, we hypothesized that this frequency would still be detectable in the MEG for the visual target sentence. In the entrainment part, we observed coherence with the prosodic contour at the stimulation rate over all MEG sensors (p < 0.001, corrected). Coherence indeed persisted into the target part (p < 0.001, corrected), with an anterior shift of the topography. Critically, when long contours were followed by short sentences, a P300 ERF was observed at the offset of the short sentence—likely indicating an omission response under the expectation of a long sentence. Together with our behavioral results, we conclude that sustained prosodic entrainment affects subsequent sentence comprehension, with the stimulation frequency being conserved by brain areas associated with higher-level linguistic processing. To substantiate the apparent shift from bottom-up (= auditory) to top-down (= predictive) brain regions, we are now conducting source reconstruction.
Topic Areas: Speech Perception, Prosody