Emotions and the Mirror Neuron System: How far can sensorimotor simulation differentiate between dynamic emotional facial expressions?

The human mirror neuron system (MNS) is becoming increasingly important to our understanding of empathy via simulation mechanisms. Despite the MNS’s growing associations with emotion processing, there are gaps in research that have yet to be explored, particularly when using sensorimotor oscillations as an index of MNS activity. This thesis aimed to reduce aspects of these knowledge gaps through three empirical studies. Experiment 1 investigated the broader MNS emotion specificity in response to the dynamic facial expressions of the six basic emotions (anger, disgust, fear, happiness, sadness and surprise) within mu frequencies (alpha and beta). Significant emotion effects were found for each basic emotion across central, frontal and parietal electrodes. Experiment 1 also investigated changes in mu suppression in response to the six basic emotions with the consideration of high versus low trait anxiety. Correlational analyses revealed trait anxiety was positively related to the happiness and sadness differentiation in mu suppression. Experiment 2 investigated whether the MNS underlies peripheral forms of motor simulation by assessing whether there was a relationship between mu suppression and facial muscle mimicry. Results did not show a consistent relationship between mu suppression and facial muscle activation; thus, suggesting that there may not be a direct connection between the MNS and facial mimicry. Experiment 3 aimed to extend emotion specificity and trait anxiety modulation mu suppression findings with a keyboard press automatic imitation (AI) task. However, this experiment was ceased due to spatial compatibility effects confounding the AI task. Overall, as a result of the thesis’s findings, it may be posited that the extended MNS is involved in the emotion classification of the six emotional facial expressions to some significant degree, which may be additionally modulated by individual differences, such as trait anxiety.