Figure 2.

Behavioral and Entrainment Effects

(A) Separate behavioral experiment on intelligibility in silent visual speech (VS) with 19 participants. The contrast hits versus chance level was significant only in the forward condition. Hits in the forward condition were also higher than hits in the backward condition.

(B) Coherences of theta-band brain sources (4–7 Hz) with the not-heard acoustic envelope of speech (AS, while watching visual speech; VS, contrasted between forward and backward conditions; p < 0.05, Monte Carlo corrected) were increased at occipital regions when watching lip movements of forward speech compared to lip movements of backward speech.

(C) Mean of the individual unheard acoustic speech-brain and lip-brain coherence values during forward and backward presentations of visual speech extracted at the voxels of the statistical effect found in (B). Difference in occipital cortex between forward and backward unheard acoustic speech-brain coherence (p < 0.000005) was statistically bigger (p < 0.005) than the forward-backward difference of lip-brain coherence during visual speech (n.s., not significant). Error bars indicate SE. ^∗∗p < 0.005 and ^∗∗∗p < 0.0005. For supporting analyses, see also Figures S1–S3.