Fig 2. MI between auditory and visual speech signals.

(A) To investigate PID in “AV congruent” condition, first MI between auditory speech and visual speech signals was computed separately for matching and nonmatching signals. MI for matching auditory-visual speech signals shows a peak around 5 Hz (red line), whereas MI for nonmatching signals is flat (blue line). The underlying data for this figure are available from the Open Science Framework (https://osf.io/hpcj8/). (B) Analysis of PID is shown for “AV congruent” condition in which both matching and nonmatching auditory-visual speech signals are present on the same brain response (MEG data). Two external speech signals (auditory speech envelope and lip movement signal) and brain signals were used in the PID computation. Each signal was band-pass filtered, followed by Hilbert transform. MEG, magnetoencephalography; MI, mutual information; PID, partial information decomposition.