In children with autism imitation problems have consistently been found (Williams et al., 2004). Combining the research on imitation in autism with the discovery of mirror neurons led to the hypothesis of a dysfunctional mirror neuron system (MNS) in individuals with ASD (Williams, Whiten, Suddendorf, & Perrett, 2001). Since imitation appears very early in development, infancy seems to be an ideal period to study the relation between imitation in development and mirror neuron functioning. However, until now, research into the MNS with infants remains scarce.
The aim of this study is to investigate mirror neuron functioning during hand movement, action observation and action imitation in very young children with a diagnosis of ASD and in siblings (age 18-30 months). Suppression in the EEG mu rhythm band is associated with the MNS activity and was previously 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 infants and infants with a diagnosis of ASD and siblings (age 18-30 months). Following Marchall and colleagues (2002) and Stroganova and colleagues (1999), we defined infant mu wave within the 6-9 Hz frequency range.
The experiment consisted of 5 blocks (with 5 different objects) and one free play situation (including all 5 objects) during which brain activity was measured with 32 active electrodes. In each block, the infants observed a moving object (object observation condition) and an experimenter performing hand movements (hand movement condition). Subsequently, infants watched (action observation condition) and imitated (action imitation condition) a simple goal-directed action with each object. At the end of the experiment infants were imitated by the experimenter while playing with the objects (free play condition). Hand movement condition and action observation/imitation were counterbalanced between subjects.
Until now, more than 40 infants participated in the study. According to preliminary results, there seems to be mu suppression during action imitation and action observation, but not during hand movement in the ASD group. In the sibling group we found the same results as in the normally developing children group which is mu suppression during action imitation. This means that despite the shared genetic material with their brother or sister with ASD, the siblings show less impairments in the functioning of their mirror neuron system than the ASD group.
Given the small number of infants in each group, the results should be interpreted with caution.
These preliminary results suggest that we developed a useful paradigm for studying mirror neuron functioning in young children. We can conclude that there is mirror neuron activity in siblings, but the mirror neuron activity seems to be less pronounced in infants with ASD in comparison with typically developing children.
Full results and conclusions will be presented at the IMFAR meeting.