Motor mirror neurons may not be a predictor of learning but reflect the effect of motor learning

The mirror neurons system (MNS) fires during both the performance of an action and observation of the same action being performed by another. On the level of motor output, activation of the MNS is thought to be represented in the phenomenon of motor resonance, which manifests in a muscle-specific increase in corticospinal excitability during action observation. This study focused on how and to what extent sensorimotor learning alters the initial mirror response and whether the rate of sensorimotor learning is associated with pretraining or post-training levels of mirror response. The study involved 23 healthy adults aged 22.7 years. The experiment consisted of six sessions. On the first and last days, a transcranial magnetic stimulation session was held to assess the putative activity of mirror neurons, as reflected in the level of motor-evoked potential facilitation during action observation in different conditions. From the second to the fifth sessions (four sessions in total), the sensorimotor learning part was performed, as represented in the form of a serial reaction time (SRT) task. We observed a statistically significant decrease of reaction time in the process of learning in the SRT task and motor facilitation during action observation, thus reflecting the process of putative mirror neurons activity. However, our data demonstrate that the sensorimotor learning rate was not associated with either pretraining or post-training estimates of motor facilitation during action observation and that sensorimotor learning does not affect the pattern of motor resonance.