UBC Theses and Dissertations
The role of mirroring and mentalizing brain systems in action understanding Hyder, Amna
Mirror neurons, which are critical for social learning, respond to both the observation and execution of an action. They do so by forming a complex brain network known as the Mirror Neuron System (MNS) in which visual neural representations of actions trigger a corresponding motor representation. Another essential feature of social learning is the ability to reason about the minds of others by inferring not just how they do something but why they are doing it. The mentalizing brain system (MZN) is implicated in the process of inferring others’ mental states5. This study utilizes high-density EEG to quantify dynamics in functional brain networks supporting mirroring and mentalizing processes in neurotypical adults. We used the photo judgement task6 which has been shown to differentiate the MNS and MZN using fMRI. Participants were shown pictures of faces or hands and asked about how (mirroring) or why (mentalizing) the actions were being performed. We see clear differences between mirroring and mentalizing tasks that can be detected by EEG. Brain activity appears to diverge around 300 ms after stimulus onset, and several EEG ERP components uniquely identify mirroring and mentalizing activity. Using mu and beta suppression as markers for mirroring and mentalizing activity respectively, the data suggests that the MNS is more active in processing action means associated with facial expressions, whereas the MZN is more active in processing intent associated with hand movements. Using microstate analysis, we show that ~300 ms after stimulus presentation, the brain undergoes several state transitions while processing intent, whereas while processing action means (mirroring), the brain appears to stay in one stable state. The neural sources of these microstates demonstrate that the how and why conditions more strongly activate regions associated with the MNS (occipital and left superior temporal gyrus) and MZN (medial prefrontal cortex) respectively. Altogether, the results show that the photo-judgement task can be used with EEG to detect differential engagement of the MNS and the MZN. The MNS appears to be more active in immediately after stimulus presentation, whereas the MZN appears to be engaged following primary context comprehension.
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