Neural Mirroring System In Young Children: An EEG Study

Background:  

Mirror neurons, discovered in the macaque brain, discharge during both execution and observation of similar actions (Di Pellegrino, Fadiga, Fogassi, Gallese, & Rizzolatti, 1992). An analogous neural mirroring system is believed to be functional in humans (Marshall & Meltzoff, 2011). According to this view, there is a direct match between the observation and execution of actions by which the motor knowledge of the observer is used to understand the observed action. Mirror neuron functioning has theoretically and/or empirically been related to action understanding (Rizzolatti & Craighero, 2004) and various social–cognitive processes such as imitation (Iacoboni, 2005), theory of mind (Iacoboni & Dapretto, 2006), language (Rizzolatti & Craighero, 2004) and empathy (Decety & Meyer, 2008). These specific skills are often impaired in individuals with ASD. This led to the hypothesis of a dysfunctional neural mirroring system in individuals with ASD. However, the findings concerning the role of these mirror neurons in ASD seems controversial and research is inconclusive.

Objectives:  

The aim of the current study is to investigate mirror neuron functioning in young children. Suppression in the EEG mu rhythm band is associated with mirror neuron activity and has been investigated in adults and children with and without ASD. In this study, we apply a child-friendly paradigm to investigate mu wave suppression during action observation and action imitation in typically developing children (TD), children with a diagnosis of ASD, and siblings of an older child with ASD (high-risk children). All children were between 4 and 5 years old.  

Methods:  

Until now, we tested 14 TD children, 13 children with ASD, and 16 siblings. The experiment consisted of 4 experimental conditions during which brain activity was measured with 73 active electrodes. The children observed a moving object (object observation condition) and an experimenter performing hand movements (HM condition). Subsequently, they observed (AO condition) and imitated (AI condition) a goal-directed action. HM condition and AO/AI condition were counterbalanced between subjects. We used brain activity data from electrodes at the positions C3, Cz and C4 for further analyses.

Results:  

In line with Marshall et al. (2010), mu wave suppression was calculated as a ratio of the mu wave power in the different conditions. Specifically, we calculated ([A - R]/R)*100 with A being mu power during the experimental conditions (AO, AI and HM condition) and R being mu power during the baseline condition (object movement condition) (Pfurtscheller & Lopes da Silva, 1999). A negative value indicates mu suppression.

Preliminary analyses show mu suppression during all three conditions in TD children, children with ASD and siblings. Full results and group comparisons will be presented at the meeting.

Conclusions:  

The results suggest that we developed a useful paradigm for studying mirror neuron functioning in young children. Children with ASD, without ASD and at risk for ASD showed mu suppression during observation of real and mimicked actions. Up till now, we found no evidence for a clear deficit in the neural mirroring system of 4-year-olds with ASD or at risk for the disorder.