Poster B41, Tuesday, August 20, 2019, 3:15 – 5:00 pm, Restaurant Hall
Cortical tracking of Mandarin structures
Chia-Wen Lo1, Tzu-Yun Tung1, Alan Ke1, Jonathan R. Brennan1;1University of Michigan
Neural responses can be entrained to linguistic structures (Ding et al., 2016, 2017). Ding and colleagues (2016) observed cortical tracking of linguistic structures at evoked frequencies corresponding to phrasal (2 Hz) and sentence structure (1 Hz) levels of Mandarin structures in continuous isochronic speech. Non-Mandarin speakers show only syllable effects only when processing the same stimuli. However, Frank & Yang (2018) suggest that these results may follow from the tracking of lexical and/or part-of-speech sequence information, not phrasal structure. For example, verbs occur at a frequency of 1 Hz while nouns occur at a 2 Hz rate. We aim to replicate Ding et al’s results using Mandarin stimuli with EEG and also test whether the results reflect lexical sequence or hierarchical information. N=31 native speakers of Mandarin Chinese listened to trials consisting of ten 4-syllable sentences. Each sentence consistent of 4 monosyllabic Mandarin words generated individually using a computer speech program. Each syllable was presented in 250 ms and thus 1 sentence is 1s in duration. Four experimental conditions were included: (1) normal four-syllable sentences, which were adopted from Ding et al. 2016 ([[Adj N] [V N] ] or [[N N] [V N]]; e.g. English gloss: “Old cattle plow ground”); (2) normal two-syllable phrases extracted from (1), (e.g. “Old cattle tree wood”); (3) semantically-mismatched sentences, made by switching words between items in (1) keeping syntactic position constant (e.g. “Soldier child run grass”); and (4) syllable scramble sequences, such that phrases were presented with a reversed word order (e.g. “Cattle old land plow”). Crucially, condition (4) maintains word-sequence patterns at 2 Hz and 1 Hz but the words do not form grammatical phrases; if neural tracking reflects sequence information, then oscillations at those bands should be equivalent between condition (4) and the regular sentences in condition (1). The first sentence from each trial was excluded to avoid potential EEG responses to sound onset. Data were manually cleaned of artifacts, filtered from 0.1-25 Hz, and re-referenced offline to common average. For each condition, we compute Evoked Power (EP), Induced Power (IP) and Inter-trial phase coherence (ITPC) from 0.5 to 10 Hz in increments of 0.111 Hz. Conditions were compared via one-way ANOVA for each measure in each frequency of interest. Results replicate Ding et al.’s finding: A sentence-level peak was shown at 1 Hz in Condition (1) only. Phrase-level peak was found at 2 Hz in Condition (1) and (3). Syllable-level peaks were shown in all conditions. Consistent with prior work, these patterns were observed for EP and ITPC but not for IP. The current study confirms that oscillatory synchronization can be modulated by linguistic hierarchical structures, not just word-sequences. Please find supporting plots here: https://www.scribd.com/document/406740993/SNL19-Plots.
Themes: Syntax, Meaning: Combinatorial Semantics
Method: Electrophysiology (MEG/EEG/ECOG)