Slide Slam M8
Neural tracking of syntax from a cross-linguistic perspective
Jordi Martorell1,2, Simona Mancini1, Nicola Molinaro1,3, Manuel Carreiras1,2,3; 1Basque Center on Cognition, Brain and Language (BCBL), 2University of the Basque Country (UPV/EHU), 3Ikerbasque
Recent findings suggest that neural activity tracks abstract syntactic structures during language comprehension. Using the frequency-tagging paradigm, it has been shown that low-frequency neural responses selectively align to the periodic presentation of multi-word chunks corresponding to syntactic phrases and sentences (Ding et al., 2016). Importantly, despite being replicated in several languages (e.g., Makov et al., 2017; Sheng et al., 2018), neural tracking of syntax has always been tested in head-initial (e.g., verb-before-object) constructions. As typologically different languages display other word order (e.g., head-final like object-before-verb) configurations, this gap clearly limits the cross-linguistic coverage of current syntax-tracking findings. In this magnetoencephalography study, we investigate neural tracking of syntactic structure from a cross-linguistic perspective. Following Ding et al., (2016), we implement the frequency-tagging paradigm but in the visual modality by periodically presenting sequences of written words to be combined into certain structures at different frequencies. Our aim is to assess whether and how neural tracking of syntax is modulated by the word order characteristics of head-initial and head-final structures in Spanish and Basque, respectively. Spanish-Basque bilinguals (n = 33) were presented with trials of 12-second sequences of 24 chunks with written words (500 ms per chunk: 350 ms display + 150 ms blank screen; single-chunk presentation frequency: ~ 2 Hz), corresponding to three different syntactic structures in either language: 1-chunk Noun Phrases (NPs; [Article Noun] in Spanish and [Noun-Article] in Basque), 2-chunk (verbal) phrases ([Verb] [NP] in Spanish and [NP] [Verb] in Basque), and 3-chunk sentences ([Auxiliary] [Verb] [NP] in Spanish and [NP] [Verb] [Auxiliary] in Basque). Our syntactic frequencies of interest were ~ 1 Hz for 2-chunk phrases and ~ 0.67 Hz for 3-chunk sentences. We report frequency-domain results of normalized power and inter-trial phase coherence (ITPC), which reflect frequency-specific neural tracking in terms of amplitude modulations and consistent phase alignment over time, respectively. Sensor-averaged results show peaks at ~ 2 Hz in all conditions, corresponding to the presentation frequency of single chunks. Moreover, 2-chunk phrases and 3-chunk sentences reveal additional peaks at ~ 1 Hz and ~ 0.67 Hz, respectively, in both Spanish and Basque. This suggests that syntax tracking emerges similarly in both languages regardless of their word order. However, certain discrepancies in the fronto-temporal sensor distribution of these effects indicate a more complex scenario. More concretely, although syntax tracking effects are distinctly lateralised (bilateral vs. left-hemispheric extension) between languages, this lateralisation also varies within each language depending on the type of syntactic structure (2-chunk phrases vs. 3-chunk sentences), suggesting the intervention of other factors beyond word order. In addition, while power and ITPC effects in 3-chunk sentences mainly show comparable distributions within each language, the sensor extension of ITPC – relative to power – effects in 2-chunk phrases is reduced considerably in Spanish and dramatically in Basque. This power-ITPC dissociation might indicate variable phase alignment to the frequency of phrases over time, particularly in Basque. Despite certain unresolved issues, our sensor-level results provide novel cross-linguistic evidence for neural tracking of syntax in head-initial as well as head-final structures.