The Influence of Body Posture on the Mirror Neuron System

Abstract

Though the mirror neuron system (MNS) is studied in the scientific community, the influence of the body posture on the functioning of the MNS, as well as on the excitatory and inhibitory system of the brain, has not been revealed yet. In our study, we investigated the functioning of the MNS in case of head rotation. Participants underwent a session of the mirror task, while they were observing movements of the little finger and the index finger of a static hand in three head positions (left, straight and right), combined with transcranial magnetic stimulation (TMS) that was applied at various time intervals. Results showed significant interactions between the movement type and the targeted muscle (F[1,113–16,688] = 9.47, MSE = 56296.14, p = .006, partial η2 = .39). This indicates a robust increase in the activation of the First Dorsal Interosseous (FDI) muscle during the index finger movement (p = .01) and the neutral movement (p .001) observation compared to the little finger movement. Conversely, a significant inhibition of the Abductor Digiti Minimi (ADM) muscle activity was observed during the index finger movement compared to neutral (p = .026). A reversed effect emerged during the little finger movement observation, with higher activation for the ADM muscle and inhibition of the FDI muscle (p = .037). These findings suggest an intricate interplay between MNS activation and muscle activation, indicating an increase in muscle activity corresponding to the observed finger movement and simultaneous inhibition of the muscle not involved in the observed movement.