EEG mu suppression in autism spectrum disorder: How valid is the broken mirror theory?

• Main Authors: Ji-Lin Liu, 劉致麟
• Other Authors: Ya-Wei Cheng
• Format: Others
• Language: en_US
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/86u53c

碩士 === 國立陽明大學 === 神經科學研究所 === 97 === Background: Mirror neuron system (MNS) plays an important role in social cognition. The “broken mirror theory” of ASD proposes that the dysfunction of MNS may result in varied social-cognitive difficulties of autism spectrum disorder (ASD) (Ramachandran et al. 2000; Williams et al. 2001). The “extreme male brain” of autism posits that ASD represents an extreme of the male brain pattern with impaired empathizing and enhanced systemizing (Baron-Cohen et al. 2005). Our previous electroencephalographic (EEG) studies had found gender differences in the human MNS as indicated by stronger mu suppression to watch hand actions in females than males (Cheng et al., 2006, 2007, 2008, 2009). Here, we also clarify if the individuals with ASD would show an extreme male pattern of MNS as shown by mu suppression during the observation of hand actions. Methods & Results: The EEG mu suppression, a reliable indicator of the activity of the human MNS, simultaneously recorded with the oculomotor analysis during the observation of baseline, hand actions, a moving dot, and self-performed hand actions in the individuals with ASD (N=20) and the controls (N=20). The results showed a significant difference of mu suppression across the conditions (the observation of hand actions, a moving dot, and self-performed hand actions) (F2, 76 = 10.812, p < 0.001) instead of the group (F1, 38 = 0.044, p = 0.835) and their interaction (F2, 76 = 2.437, p = 0.094). The ASD group was not different from the control group, which also exhibited stronger mu suppression during the observation of hand actions than other conditions. In addition, the mu suppression during the observation of hand actions has a positive correlation with the domain of verbal communication (Pearson r = 0.488, p = 0.034). Discussion & Conclusion: The present findings suggested that the individuals with ASD preserved MNS to a degree, which, in turn, may provide direct evidence against the broken mirror theory of ASD. The imitation behavior as well as the failure to imitate in ASD, should involve more than the MNS. Better cognitive model within and beyond MNS are required to understand the pathogenesis of social reciprocity difficulties in ASD.