Exploring motor system contributions to the perception of social information: Evidence from EEG activity in the mu/alpha frequency range

Abstract

Putative contributions of a human mirror neuron system (hMNS) to the perception of social information have been assessed by measuring the suppression of EEG oscillations in the mu/alpha (8–12 Hz), beta (15–25 Hz) and low-gamma (25–25 Hz) ranges while participants processed social information revealed by point-light displays of human motion. Identical dynamic displays were presented and participants were instructed to distinguish the intention, the emotion, or the gender of a moving image of a person, while they performed an adapted odd-ball task. Relative to a baseline presenting a nonbiological but meaningful motion display, all three biological motion conditions reduced the EEG amplitude in the mu/alpha and beta ranges, but not in the low-gamma range. Suppression was larger in the intention than in the emotion and gender conditions, with no difference between the latter two. Moreover, the suppression in the intention condition was negatively correlated with an accepted measure of empathy (EQ), revealing that participants high in empathy scores manifested less suppression. For intention and emotion the suppression was larger at occipital than at central sites, suggesting that factors other than motor system were in play while processing social information embedded in the motion of point-light displays.

Keywords:

• Mu rhythms
• Alpha
• Biological motion
• Motor system
• Social skills

We thank Dori Bar-On for skillful assistance in running the experiment, NSERC for funding NFT, and the “Hoffman Leadership and Responsibility” fellowship program, at the Hebrew University, for partially funding AP.

Notes

¹ Our definition of “action” in the present context is sufficiently broad to include anything from a particular body posture to the dynamics involved in facial expressions and whole body movements.

² Although it is conceivable that the gender of an agent has a social value, this value is probably less related to simulation, considering that one has only experienced being either male or female. We did check for an interaction between the gender of the participant and that of the stimuli, but no such interaction was found.

³ The same analysis was also done for the whole 5 s and for the middle 4 s, yielding the same results.