Differential Responses In The Mirror Neuron System During Imitation Of Individual Emotional Facial Expressions And Association With Autistic Traits In FNIRS Study

Imitation is defined as the repetition of observed facial expressions,movement and actions.In general,imitative behaviors consist of two different types: movement or action imitation and expression imitation.The latter one helps people to recognize other emotions and provides a basis for inferring and understanding the specific emotion that the expresser conveys.The mirror neuron system(MNS),including the inferior frontal gyrus(IFG),inferior parietal lobule(IPL)and superior temporal sulcus(STS),plays an important role in action representation,expression imitation,even empathy.however,it’s not clear how these three MNS regions respond and interact during the imitation of different basic facial expressions and whether the pattern of responses is influenced by autistic traits.Thus,we explored the activation of the MNS in the process of imitating different emotions by collecting the behavioral data and fNIRS data of 100 normal college students when imitating facial expressions.Next,we compared the differences in cosine similarity and functional connectivity between regions of the MNS while imitating happy expressions vs other facial expressions.In the last,we treated the functional connectivity as features and predicted autism trait scores by using support vector regression.The results showed that imitation of happy expressions produced the highest expression intensity but a small deactivation in MNS responses,suggesting a lower processing requirement compared to other expressions.A cosine similarity analysis indicated a distinct pattern of MNS responses during imitation of each facial expression with functional intra-hemispheric connectivity between the left IPL and left STS being significantly higher during happy compared to other expressions,while inter-hemispheric connectivity between the left and right IPL differed between imitation of fearful and sad expressions.Furthermore,functional connectivity changes during imitation of each different expression could reliably predict autistic trait scores.Overall,the results provide evidence for distinct patterns of functional connectivity changes between MNS regions during imitation of different emotions which are also associated with autistic traits.