Motor-resonance in response to action-related visual and audio stimuli: A fMRI study of identical twins discordant for music training

• ¹ Karolinska Institute, Neuroscience, Sweden

Background: The human mirror neuron system (MNS) contains visuomotor neurons that are active during task execution as well as during observation of a goal directed motor task. Although more recently there has been some evidence that these premotor areas are also active when listening to action-related sounds, the representation of sound in the MNS is not well understood. To our knowledge no study has directly explored differences in activation of the MNS in response to visual, auditory or combined audio-visual cues related to the same action. Further, little is known about the importance of familiarity with a task for the human action-recognition system.
Methods: A sample of identical twins discordant for long-term piano training (one twin with musical education while the co-twin was musically untrained) was utilized to further the understanding of audio- and visuo-motor recognition in the human brain. This allows for within-pair (controlling for genetic factors), in addition to between conditions comparisons of brain activity in response to different stimuli (auditory and visual). Participants were trained to play an eight-tone melody consisting of four notes with four fingers of their right hand – one tone per finger. After training, brain activity was measured using functional magnetic resonance imaging (fMRI) while participants passively were exposed to visual (a hand playing a melody on a piano), auditory, or visuo-auditory (combined) action-related stimuli. The stimuli consisted of either the learned melody, a new sequence (consisting of the same four notes), or an incongruent stimulus where the auditory (learned) and visual (new) stimuli did not match.
Results and Discussion: Results of the present study will address the following issues: (1) differences/similarities in activation of the MNS based on auditory versus visual action related cues; (2) how does multisensory (visuo-auditory learned, novel or incongruent) stimulation compare to uni-sensory stimulation, for example, is the activation seen in response to learned audio-visuo cues the sum of audio- and visuo-motor recognition separately? and (3) what is the effect of long-term training on the MNS (within-pair comparison of the discordant twins)? Findings will be discussed in light of the past literature.