Oberman et al. (2005)used EEG to record mu waves over the motor cortex of high-functioning autisticchildren and controls. Mu oscillations occur at a particular frequency (8–13 Hz)and are greatest when participants are doing nothing. However, when they performan action there is a decrease in the number of muwaves, a phenomenon termed mu suppression.Importantly, in typical controls mu suppressionalso occurs when people observe actions and, assuch, it has been regarded by some as a measureof mirror-system activity (Pineda, 2005). Obermanet al. (2005) found that the autistic children failedto show as much mu suppression as controlsduring action observation (watching someone elsemake a pincer movement) but did so in the controlcondition of action execution (they themselvesmake a pincer move ment). Finally, watchingsomeone perform an action increases ones ownmotor excitability, measured as a motor-evokedpotential (MEP) on the body, when TMS isapplied to the motor cortex. However, this effectis reduced in autistic people, even though theirmotor cortex behaves normally in other contexts(Theoret et al., 2005).