Complex sentence: Some mirror neurons are not only activated by the observation of goal-directed actions, but also by the associated sounds produced during the action, indicating that the auditory modality can access the motor system Kohler, E. et al.
Split into simpler sentences: Some mirror neurons are activated both by the observation of goal-directed actions, and by the associated sounds produced during the action. This suggests that the auditory modality can access the motor system Kohler, E. et al.