Figures and data
A. Experimental procedure and multivariate statistical analyses. The learning part was sandwiched by a silent resting state (RS) and a random stream (RND) with even transition probabilities between syllables. This design accounted for the potential effect of time during the experiment and changes in vigilance state on neural entrainment measures. The learning segment consisted of a long structured (STR) stream where syllables were organized into four three-syllable words presented in random order with no repetition. Following this, six test-blocks were presented, each comprising 8 triplets from the words and part-words conditions with 2-second silences interleaved between items. To sustain learning, 30-second short STR streams were interspersed between test blocks. A 4.5s fade-in/out at the borders of each stream was included to minimize any perceptual anchor effect. The full procedure lasted ∼17 minutes. Arrows’ width schematically represents the transition probability magnitude. B. Pipeline for longitudinal partial least square correlation (PLS-c) analysis. Details are provided in the Methods section.
Neural entrainment to syllable rate (4 Hz): Main effect across all participants (Top row); Group differences (bottom row).
A. Design salience (left) and brain salience (right topography) derived from the significant latent component for neural entrainment to the syllable rate (4 Hz) using the targeted frequency (4 Hz) versus adjacent frequencies as a contrast. Significance (i.e., salience) was established through bootstrapping. Bars represent the mean of 500 random salience samples with replacement bootstrapping, and error bars indicate the 95% confidence interval. Yellow shading highlights variables that significantly contribute to the latent component, defined by a Bootstrap Ratio (BSR; mean of bootstrapping divided by standard deviation) > 2.3. The topography of the BSR values shows electrodes significantly contributing to the latent component (indicated by black dots, BSR > 2.3). B. Individual raw Phase Locking Values (PLVs) extracted from the salient electrodes identified by the latent component (black dots in the topography on 2A) are displayed. A fitted curve is included for visualization purposes only, produced by a mixed-effects model with a 95% confidence interval. This curve is intended solely to aid visualization, as the statistical relationships between EEG and behavioral variables are determined by the PLS-C analysis. C. PLS-C analysis of the differences between HL and LL groups is presented following the same format as in A. D. Individual raw PLVs extracted from the salient electrodes (black dots in subfigure 2C) are shown for visualization purposes only. At every age, a verbal developmental quotient (DQ) of 100 is expected in the general population.
Neural entrainment to word rate (1.3Hz): Main effect across all participants
(Top row); Group differences (bottom row). A. Design salience (left) and brain salience (right) derived (through bootstrapping) from the significant latent component for neural entrainment to word rate. B. Individual raw PLVs extracted from the salient electrodes given by the latent component (black dots on subfigure A) with a fitted curve, for visualization purposes only. C. PLS-c applied on PLV at 1.3Hz with adjacent frequencies subtracted, using group as contrast, and verbal outcome (verbal developmental quotient [DQ] collected at 18-21 months) added as a design variable. D. Raw individual data extracted from the salient electrodes of the latent component (black dots on subfigure 2C) with a linear regression curve fitted for illustration purpose only.
Early evoked response potential (ERP) to part-words compared to words across all participants.
A. Design and brain saliences derived from the significant latent component. Brain topographies of bootstrap ratios (BSR) are displayed at 250ms intervals. Black dots indicate BSR > 2.3. B. Participants’ brain scores for part-word and word conditions, as a function of age. Brain scores are participants’ raw voltage data projected onto electrode saliencies. Brain scores illustrate how individual EEG data fit the saliences derived from the latent component. Linear fitting is used for illustrative purposes only. C. Voltage grand averaged (left) and differential (right) responses to part-word and word conditions at each age bin: 3 months (n=18), 6-9 months (n=20), 12-15 months (n=20), 18-21 months (n=25).
Late evoked response potential (ERP) to part-words compared to words across all participants.
A. Design and brain saliences derived from the significant latent component. Brain topographies of bootstrap ratios (BSR) are displayed at 250ms intervals. Black dots indicate BSR > 2.3. B. Participants’ brain scores for part-word and word conditions, as a function of age. For details, see figure 4. C. Voltage averaged (left) and differential (right) responses to part-word and word conditions at each age bin: 3 months (n=18), 6-9 months (n=20), 12-15 months (n=20), 18-21 months (n=25).
Late evoked response potential (ERP) to novelty in infants at high and low likelihood for autism.
A. Design and brain saliences derived from the significant latent component. Brain topographies of bootstrap ratios (BSR) are displayed at 250ms intervals. Black dots indicate BSR > 2.3. B. Participants’ brain scores for part-word and word conditions, as a function of age (left) and of verbal outcome (right). Detailed information about brain scores is provided in Figure 4. Linear fitting is used for illustrative purposes only. C. Voltage differential responses to part-word and word conditions at each age bin and within each group: 3 months (11 LL and 7 HL), 6-9 months (9 LL and 11 HL), 12-15 months (10 LL and 10 HL), 18-21 months (9 LL and 16 HL). DQ: developmental quotient. HL: high likelihood for autism; LL: low likelihood for autism.
Sample characteristics.
Statistical comparison between LL and HL samples. For categorical variable, chi square (χ2) was applied. For continuous variables, we used two-tailed independent T tests. P values < .05 are highlighted in bold.
Follow-up analyses restricted to each stream for syllable entrainment.
A. For RND, the latent component was significant (p<.001; r=.67; 87.3% explained covariance) with the following BSRs: contrast : 70.3*; mean age: -1.6; contrast*mean age: -0.7; delta age: 3.6*; contrast*delta age: 8.0*; age2: 1.2; contrast*age2: -4.1*. B. For STR, the latent component was significant (p<.001; r=.73; 91.1% explained covariance) with the following BSRs: contrast : 91.4*; mean age: -.9; contrast*mean age: 0.7; delta age: 4.2* contrast*delta age: 4.7*; age2: -2.4; contrast*age2: -3.8*. Yellow shading on left panels and black dots on middle panels indicate BSR > 2.3 – BSR >2.3 is considered significant.
Neural entrainment to syllable rate in sleeping participants (n=25 recordings).
A. Design salience (left) and brain salience (right topography) derived from the significant latent component for neural entrainment to the syllable rate using frequency (4hz versus adjacent frequencies) as contrast. Significance (i.e., salience) was established through bootstrapping. B. Individual raw Phase Locking Values (PLVs) extracted from the salient electrodes identified by the latent component (black dots in the topography on 2A) are displayed. A fitted curve is included for visualization purposes only, produced by a mixed-effects model with a 95% confidence interval.
Neural entrainment to syllable rate (4 Hz), excluding the final visit (n=54 recordings).
A. Design salience (left) and brain salience (right topography) derived from the significant latent component for neural entrainment to the syllable rate (4 Hz) using group (low versus high-likelihood for autism) as contrast. Significance (i.e., salience) was established through bootstrapping. Bars represent the mean of 500 random salience samples with replacement bootstrapping, and error bars indicate the 95% confidence interval. Yellow shading highlights variables that significantly contribute to the latent component, defined by a Bootstrap Ratio (BSR; mean of bootstrapping divided by standard deviation) > 2.3. The topography of the BSR values shows electrodes significantly contributing to the component (indicated by black dots, BSR > 2.3). B. Individual raw Phase Locking Values (PLVs) extracted from the salient electrodes identified by the latent component (black dots in the topography on 2A) are displayed. At every age, a verbal developmental quotient (DQ) of 100 is expected in the general population. A fitted curve is included for visualization purposes only, produced by a mixed-effects model with a 95% confidence interval. This curve is intended solely to aid visualization, as the statistical relationships between EEG and behavioral variables are determined by the PLS-C analysis.
Neural entrainment to word rate in sleeping participants (n=25 recordings).
A. Design salience (left) and brain salience (right topography) derived from the significant latent component for neural entrainment to the word rate using frequency (1.3hz versus adjacent frequencies) as contrast. Significance (i.e., salience) was established through bootstrapping. B. Individual raw Phase Locking Values (PLVs) extracted from the salient electrodes identified by the latent component (black dots in the topography on A.) are displayed. A fitted curve is included for visualization purposes only, produced by a mixed-effects model with a 95% confidence interval.
Word entrainment within HL participants (n=25; 44 recordings).
A. Design salience (left) and brain salience (right topography) derived from the significant latent component for neural entrainment to the word rate using frequency (1.3hz versus adjacent frequencies) as contrast. Significance (i.e., salience) was established through bootstrapping. BSRs: contrast : 12.9*; mean age: -3.2*; contrast*mean age: -5.3*; delta age: 5.9*; contrast*delta age: 6.7*; age2: 3.6*; contrast*age2: 1.9. B. Individual raw Phase Locking Values (PLVs) extracted from the salient electrodes identified by the latent component (black dots in the topography on A.) are displayed. A fitted curve is included for visualization purposes only, produced by a mixed-effects model with a 95% confidence interval.
Late evoked response potential (ERP) to word novelty, excluding the final visit (n=54 recordings).
A. Design and brain saliences derived from the significant latent component. Brain topographies of bootstrap ratios (BSR) are displayed at 250ms intervals. Black dots indicate BSR > 2.3. B. Participants’ brain scores for part-word and word conditions, as a function of verbal outcome. Brain scores are participants’ raw voltage data projected onto electrode saliencies. Brain scores illustrate how individual EEG data fit the saliences derived from the latent component. Linear fitting is used for illustrative purposes only. HL: high likelihood for autism; LL: low likelihood for autism.
Late evoked response potential (ERP) to word novelty within low likelihood infants (n=19; 39 recordings)
A. Design and brain saliences derived from the significant latent component. Brain topographies of bootstrap ratios (BSR) are displayed at 250ms intervals. Black dots indicate BSR > 2.3. B. Participants’ brain scores for part-word and word conditions, as a function of age. Brain scores are participants’ raw voltage data projected onto electrode saliencies. Brain scores illustrate how individual EEG data fit the saliences derived from the latent component. Linear fitting is used for illustrative purposes only. LL: low likelihood for autism.
Late evoked response potential (ERP) to word novelty within high likelihood infants (n=25; 44 recordings)
A. Design and brain saliences derived from the significant latent component. Brain topographies of bootstrap ratios (BSR) are displayed at 250ms intervals. Black dots indicate BSR > 2.3. B. Participants’ brain scores for part-word and word conditions, as a function of age. Brain scores are participants’ raw voltage data projected onto electrode saliencies. Brain scores illustrate how individual EEG data fit the saliences derived from the latent component. Linear fitting is used for illustrative purposes only. HL: high likelihood for autism.
Neural entrainment data quality.
LL mean trajectory is in red and HL in blue, with their respective 95% confidence intervals. Included epochs in absolute number.
ERP data quality.
LL mean trajectory is in red and HL in blue, with their respective 95% confidence intervals.
Neural entrainment time course over the experimental session considering all participants.
The plain squares under the plots correspond to the time samples with PLVs significantly greater than 0 (p<.05).
Group differences in the time course of syllable neural entrainment (4Hz).
Gray shading on right panel indicates BSR < 2.3; BSR >2.3 is considered significant. Vertical dashed lines indicate the transitions between random and structured streams.
Syllable entrainment within RND (A-B) and STR (C-D).
ERP topographies across age bins and participants
ERP topographies in each group at 3mo and 6-9mo
