Sensitivity of ‘mu’ rhythm modulation to the relevance of an observed movement but not to goal congruency

There is some dispute over whether the primary role of a system that processes both performed and observed actions (the mirror neuron system) is action understanding or the coordination of action with others. We present behavioural and EEG data from a motor priming task that shed some light on this debate. Participants are asked to make one of two simple actions whilst watching video clips of movements that differ in terms of their visuospatial overlap with, and goal-related relevance to, the required performed action. The reaction time data appear to support a direct matching account where visuospatial overlap is prioritised over relevance. However, the EEG data appear to reflect a system that is sensitive to the relevance of the observed movement and suggest an action prediction role for a mirror neuron system.

► This study examines Mirror Neuron System activation using EEG and reaction times.
► The experiment modulates task related relevance and visuospatial overlap.
► Visuospatial overlap modulates reactions times and relevance modulates the EEG data.
► We suggest a two system approach to interpreting the data.