Prenatal experience with language shapes the brain

Supplementary analyses describe linear mixed effects models assessing DFA exponent (DFAexp) as a function of a Silence factor with random intercepts and random slopes by Subject, examined in Theta and Gamma bands. Model selection involved AIC comparisons of models including the fixed effect of Silence and random effects structure (1 + Silence | Subject). Stimuli included English sentence sets (e.g., “The bears lived all together in a beautiful house,” “The bears decided to take a walk that day,” “The little bears saw that their chairs were used by the naughty girl”). Acoustic measurements (duration, syllabic rate, pitch) for the stimuli are reported (Fig. S1).

Theta band (Table S2):

• All subjects: Silence slope = 0.050, SE = 0.013, t = 3.87, p = 0.0005.
• Last language: French: Silence slope = 0.065, SE = 0.013, t = 4.94, p = 0.0003.
• Last language: Spanish: Silence slope = 0.052, SE = 0.032, t = 1.64, p = 0.14 (n.s.).
• Last language: English: Silence slope = 0.036, SE = 0.023, t = 1.54, p = 0.15 (n.s.). Gamma band (Table S5 excerpts):
• Last language: Spanish: Silence slope = -0.015, SE = 0.055, t = -0.27, p = 0.79 (n.s.).
• Last language: English: Silence slope = -0.136, SE = 0.038, t = -3.60, p = 0.004.

In the Theta band, the Silence factor shows a significant positive effect across all subjects and specifically within the French last-language subgroup, while effects are not significant for Spanish and English subgroups. In the Gamma band, a significant negative Silence effect is observed for the English subgroup, with no significant effect for the Spanish subgroup. These subgroup-specific patterns indicate that neural metrics (DFA exponent) are differentially modulated by Silence across frequency bands and language groups in the supplementary analyses.

The supplementary results report linear mixed effects analyses of DFA exponent revealing a significant positive effect of Silence in the Theta band overall and for the French subgroup, and a significant negative effect in the Gamma band for the English subgroup. Stimulus acoustic properties were documented. Further work may explore mechanisms underlying band- and language-specific effects and extend analyses across additional groups and conditions.