Mu rhythm suppression reflects mother-child face-to-face interactions: a pilot study with simultaneous MEG recording

Abstract

Spontaneous face-to-face interactions between mothers and their children play crucial roles in the development of social minds; however, these inter-brain dynamics are still unclear. In this pilot study, we measured MEG mu suppression during face-to-face spontaneous non-linguistic interactions between mothers and their children with autism spectrum disorder (ASD) using the MEG hyperscanning system (i.e., simultaneous recording). The results demonstrated significant correlations between the index of mu suppression (IMS) in the right precentral area and the traits (or severity) of ASD in 13 mothers and 8 children (MEG data from 5 of the children could not be obtained due to motion noise). In addition, higher IMS values (i.e., strong mu suppression) in mothers were associated with higher IMS values in their children. To evaluate the behavioral contingency between mothers and their children, we calculated cross correlations between the magnitude of the mother and child head-motion during MEG recordings. As a result, in mothers whose head motions tended to follow her child's head motion, the magnitudes of mu suppression in the mother's precentral area were large. Further studies with larger sample sizes, including typically developing children, are necessary to generalize this result to typical interactions between mothers and their children.

Figure 1. Mu rhythm amplitude in precentral areas of mothers and children.

(a) mu rhythm (10–12 Hz) amplitude in the precentral area in mothers (n = 13). (b) mu rhythm (8–10 Hz) amplitude in the precentral area in children (n = 8). (c) mu rhythm (10–12 Hz) amplitude in the precentral area in children (n = 8). The black bar indicates the DVD condition. The gray bar indicates the face-to-face condition. The index of mu suppression (IMS) was calculated using the following formula: IMS = mu rhythm power (DVD - Live). The error bar represents the standard error of the mean.

Figure 2. Scatter plot of the IMS in right hemisphere and the autistic traits.

(a) Scatter plot of the IMS in the right hemisphere and the AQ score in the mothers. Spearman’s rank correlation coefficient was significant (n = 13, ρ = 0.78, p = 0.002). (b) Scatter plot of IMS in the right hemisphere and the SRS total T-score in children. Spearman’s rank correlation coefficient was significant (n = 8, ρ = 0.76, p = 0.028).

Figure 3. Whole-brain statistical maps of IMS.

From the results of Spearman’s rank correlation analysis between the IMSs in all brain areas corresponding to 68 freesurfer Desikan-Killiany atlas regions and the AQ total score (in the mothers) or SRS total T-scores (in the children), a significant correlation was found in the brain area located close to the central sulcus in the right hemisphere (p < 0.05) in mothers (a) and children (b). The color bar indicates ρ-values.

Figure 4. Cross-correlation coefficients in 8 mother-child pairs.

Data represent the cross-correlation coefficients of each of the 8 mother-child pairs. The ordinate axis represents the cross-correlation coefficient, and the abscissa represents the directionality. A positive peak value of the correlation coefficient in the abscissa axis indicates that the “mother tends to follow her child”, a negative peak value indicates that “mother tends to lead her child”, and a 0 indicates that there is a “tendency for no time-lag between the head motions of the mothers and their children”.