EEG mu rhythm and TMS induced motor evoked potentials in the measurement of the perception/execution matching system: A neuronavigated study

Lepage, JF; Saint-Amour, D & Théoret, H
Centre de Recherche en Neuropsychologie et Cognition, Université de Montréal, Canada 
Centre de Recherche CHU Ste-Justine, Montréal, Canada.

It is now well established that the human brain is endowed with a system that matches the observation of action with its execution. To investigate this mechanism, the EEG mu rhythm modulation (8-12Hz) and TMS induced motor evoked potentials (MEPs) are two techniques commonly used in cognitive studies. While both techniques have reliably demonstrated similarities in the patterns of activity induced by action production and action observation, the relationship they bear with each other remains elusive. In the present study, we combined ongoing EEG recording and single pulse TMS induced MEPs during the execution, the imagination and the observation of simple hand actions. Relationship between MEPs and EEG frequency bands, namely the mu rhythm, were investigated. Our results replicate those obtained independently with both techniques, namely a significant increase in MEPs amplitude during action observation, imagination and execution compared to rest, and a significant attenuation of mu rhythm during these same conditions. Surprisingly, we found a lack of significant correlation between MEPs amplitude and mu rhythm in all conditions studied. However, modulations in the low to midrange beta band (12-18Hz) were related to MEPs size during rest and execution conditions. These results suggest that although both EEG and MEPs techniques seem to be sensitive to motor resonance mechanisms, they may reflect different processes taking place within this system.