Motor corticospinal excitability during the observation of interactive hand gestures.

The observation of other's behaviour results in increased corticospinal excitability (CSE) within the primary motor cortex, a phenomenon that has typically been interpreted in the context of motor resonance and human "mirror systems". Mirror systems are implicated in empathy, and may therefore show a preferential response to the observation of interactive behaviour. Participants were administered transcranial magnetic stimulation (TMS) to the primary motor cortex while viewing matched hand movements with or without (1) an interactive context and (2) an interactive context with an implied heightened emotional aspect. CSE was not enhanced when viewing interactive (compared with individual) hand movements. There was, however, some evidence for an enhanced response when viewing hand movements with an emotional component. There was no association between mirror systems and self-reported empathy. Mirror systems may not be more responsive to interactive behaviour, but the inclusion of a strong emotional element could be of significance to mirror neurons.