Anatomical localization of the sEEG electrodes for each patient projected in MNI space on the lateral 3D view (top) and on the top view (N=16).

Paradigm and coordination indexes.

(A) Top: illustration of one trial of the interactive synchronous speech repetition task (orange: virtual partner speech; blue: participant speech; stimulus papi m’a dit repeated 10 times ; only the 10 first seconds are represented). Bottom: the four speech utterances used in the task and the experimental procedure. (B) Speech signals processing stages. The top panel corresponds to the speech envelope, the second to the phase of speech envelope and the third panel to the phase difference between VP and participant speech envelopes, illustrating the coordination dynamics along one trial. (C) Left: distributions of verbal coordination index (phase locking values between VP and participant speech envelopes, for each trial) for all participants (top) and patients. Right: boxplots for control participants (top) and patients showing the trial- averaged verbal coordination index as a function of the virtual partner parameters (in-phase coupling vs coupling with a 180° shift).

Power spectrum analyses and correlation with verbal coordination index (left hemisphere).

Each dot represents a channel where a significant effect was found either on (A) Global activity (Task versus Rest) for each frequency band. The activity is expressed in % of power change compared to resting; or on (B) Behaviour- related activity: r values of the Spearman correlation across trials between the iEEG power and the verbal coordination index (VCI). (C) The proportion of channels where a significant effect was found: in the task vs rest (orange), in the brain-behaviour correlation (green) or for both comparison (blue). The percentage in the center indicates the overall proportion of significant channels from the three categories with respect to the total number of channels.

Group analysis by regions of interest for the left hemisphere.

(A) Regions of interest (ROI) defined according to the cluster analysis (see Figure S3), the delimitation of regions is based on the Brainnetome atlas. (B) For each ROI, boxplots illustrate, in red, channels with significant global power changes (HFa, task vs rest) and, in blue, their corresponding r values (correlation between HFa power and verbal coordination index, VCI). Red and blue stars indicate a significant difference from a null distribution. Dots represent independent iEEG channels. The « n » below each region of interest specifies the number of patients. STG : superior temporal gyrus ; IPL : inferior parietal lobule ; IFG : inferior frontal gyrus ; BA : brodmann area.

Phase-amplitude coupling between virtual partner speech signal or coordination dynamics and high frequency activity (HFa).

A) Representation of the increase in PAC expressed in % compared to surrogates mean when using the virtual partner speech (left) or the coordination dynamics (phase difference between VP and patient, right). The shaded (slight blue) area corresponds to the location of the IFG BA44. B) PAC values for VP (in red) and phase difference (in blue) by regions of interest. Statistical difference between the two types of PAC is calculated using paired Wilcoxon’s test (STG BA41/42 : p=.01 ; STG BA22 : p=.004 ; IPL BA40 : p=.6 ; IFG BA44 : p=.02). Y-axis range has been adjusted to better illustrate the contrast between VP speech and coordination dynamics.

Distribution of verbal coordination index for each patient (PLV between patient’s speech and VP speech).

For each of the sixteen patients, this figure depicts the histogram of the coordination index for all trials (in blue) as well as the null distribution (random phase shift) computed using 500 permutations per trial (in red).

Power spectrum analyses and correlation with verbal coordination index (right hemisphere).

Each dot represents a channel where a significant effect was found either on (A) Global activity (Task versus Rest) for each frequency band. The activity is expressed in % of power change compared to resting; or on (B) Behaviour- related activity: r values of the Spearman correlation across trials between the iEEG power and the verbal coordination index (VCI). (C) The proportion of channels where a significant effect was found: in the task vs rest (orange), in the brain-behaviour correlation (green) or for both comparison (blue). The percentage in the center indicates the overall proportion of significant channels from the three categories with respect to the total number of channels.

Cluster analysis (silhouette score).

Illustration of the mean silhouette scores according to the number of clusters for global activity (in red) and behaviour-related activity (correlation between power changes and coordination index, in blue). The highest silhouette score was obtained for five clusters in the HFa range for behaviour-related activity (framed in full black square). Bottom right: spatial cluster representation for the highest mean silhouette score value in HFa range.

Group analysis by regions of interest (right hemisphere).

For each ROI, boxplots illustrate, in red, channels with significant global power changes (HFa, task vs rest) and, in blue, their corresponding r values (correlation between HFa power and verbal coordination index, VCI). Red and blue stars indicate a significant difference from a null distribution. Dots represent independent iEEG channels. The « n » below each region of interest specifies the number of patients. STG : superior temporal gyrus ; IPL : inferior parietal lobule ; IFG : inferior frontal gyrus ; BA : Brodmann area.

Phase-Amplitude Coupling analyses by region of interest (right hemisphere).

PAC expressed in % compared to surrogates when using as phase the virtual partner speech (in red) or the coordination dynamic (phase difference between VP and participant, in blue) and as amplitude the high frequency activity. Statistical difference between the two different types of PAC is calculated using paired wilcoxon test (STG BA41/42 : p<0.0001 ; STG BA22 : p=0.9 ; IPL BA40 : p=0.2 ; IFG BA44 : p=0.01). Y-axis range has been adjusted to better illustrate the contrast between VP speech and coordination dynamic.

Phase-Amplitude Coupling according to the behavioural delay (left hemisphere).

PAC expressed in % compared to surrogates when using as phase the coordination dynamic (phase difference between VP and participant) and as amplitude the high frequency activity. Comparison between PAC on trials with negative and positive delays (see “Coupling behavioural and neurophysiological data” section in Materials and methods). Please note that the y-axis range has been adjusted per panel.