Article Figures & Data
Figures
- Figure 1.
Schematic illustration of the experimental materials and procedures. A, Speech stimuli were sentence sequences. Each sentence consisted of a noun phrase (NP) and a verb phrase (VP), and each phrase contained two 250-ms syllables (Syl). Using EEG, we tested the neural activities at the tagged frequencies of 1, 2, and 4 Hz corresponding to the rhythm of sentences, phrases, and syllables, respectively. B, The spectrum for sound intensity showed a significant peak at 4 Hz (p < 0.001), corresponding to the syllable-level fluctuations of the speech. The shaded area represents the standard error (SE) across the 48 speech sequences. ***p < 0.001. C, Experimental protocol. In the active-listening block, participants listened carefully to the speech stimuli and responded to a comprehension question. In the passive-listening block, they concentrated on a silent movie while ignoring the sound. Details of language background of L2 participants are provided in Extended Data Figure 1-1.
- Figure 2.
Neural tracking of linguistic structures at syllabic, phrasal, and sentential rates. A, Significant peaks were observed at 1, 2, and 4 Hz in the L1 group, reflecting neural tracking of sentential, phrasal, and syllabic structures in both active-listening and passive-listening conditions. B, In the L2 group, there was robust tracking of the lower-level syllabic-rate fluctuations at 4 Hz and a significant response at the phrasal rate of 2 Hz in the active-listening condition. Shaded areas represent SE; *p < 0.05, **p < 0.01, ***p < 0.001. C, Topographic plots of EEG peak response at tagged frequencies showed whole-brain speech cortical tracking with a general central-frontal distribution. The EEG peak response relative to the average of their four neighboring bins (two at each side) is displayed. There was no difference in hemispheric lateralization between the left-handed and right-handed L2 learners (Extended Data Fig. 2-1).
- Figure 3.
Comparisons of the frequency-tagged neural tracking response between groups. A, The L1 listener’s neural tracking response was stronger in active listening than in passive listening at all tagged frequencies, while the L2 learner’s tracking response was enhanced by attention at a phrasal rate of 2 Hz. B, Neural tracking responses in L2 were weaker than those in L1, especially when attentional resources were allocated to the speech stream. Error bars represent SE; *p < 0.05, **p < 0.01.
- Figure 4.
Attentional modulation of speech cortical tracking in L1 and L2. Reduced neural tracking of linguistic structures in L2 relative to L1 was observed in the active-listening condition but not in the passive-listening condition. After normalizing the attentional effect at tagged frequencies, we found less attentional gain in L2 than L1. Data are displayed as box-whisker plots (box, 25/75% percentiles; whisker, 10/90% percentiles; line, median; square dot, mean). Circles indicate values outside the 10th–90th percentile range; * p < 0.05.
- Figure 5.
Correlation between language proficiency and cortical tracking of L2 speech. Pearson correlation analysis revealed that the oscillatory neural tracking at the phrase-level frequency (2 Hz) but not at the syllable-level frequency (4 Hz) was correlated with L2 language proficiency. *p < 0.05, # marginally significant; n.s., not significant.
- Figure 6.
Tracking responses in L2 subgroups whose L1 was English (n = 7), French (n = 5), Samoan (n = 4), or Nepali (n = 4). For all subgroups, a paired-sample t test showed no significant attentional effect at either 2 or 4 Hz (all p > 0.05). The shaded areas and error bars represent the SE. A connecting line between two dots indicates data from the same individual. act: active; pas: passive.
Extended Data
Extended Data Figure 1-1
Detailed language background of the 24 subjects in the L2 group. We asked participants to report their native language as well as other languages acquired in addition to their native language and Mandarin Chinese. Participants in the L2 group varied in their native language, which included English (n = 7), French (n = 5), Nepali (n = 4), Samoan (n = 4), Spanish (n = 1), Urdu (n = 1), Chichewa (n = 1), and Bengali (n = 1). We were primarily interested in participants’ L2 processing of Mandarin Chinese and the comparison of processing between native speakers (the L1 group) and nonnative speakers (the L2 group) that differed in proficiency, regardless of their language background. Thus, the variation in language background did not bias the findings of our study. Download Figure 1-1, DOCX file.
Extended Data Figure 2-1
Hemisphere lateralization of speech cortical tracking in left-handed and right-handed L2 subjects. Hemisphere lateralization effect was calculated by subtracting the EEG peak response (calculated relative to the average of the four neighboring bins; two on each side) in the left hemisphere from that in the right hemisphere. The hemisphere lateralization effect of the left-handed L2 subjects (n = 5) and the right-handed L2 subjects (n = 19) in each condition were compared using independent-sample t tests. There was no significant difference of hemispheric lateralization between the left-handed and right-handed L2 learners. Download Figure 2-1, DOCX file.
In this issue
