Joint actions, in which two or more people coordinate their actions with each other to achieve a common goal, are ubiquitous in daily life. Examples range from moving furniture with a friend to musical ensemble performance. Despite the ubiquity of joint actions, researchers know relatively little about the underlying neural processes that operate during real-world, dynamic joint action. Furthermore, recent research emphasizes the importance of using one’s own sensorimotor system to represent and simulate others’ contributions to the joint action to facilitate coordination. However, the notion that people represent their own and others’ contributions to a joint action using the same neural resources raises the question of how people nevertheless maintain a distinction between each person’s individual contributions. This dissertation will focus on delineating neural markers of self-other differentiation during dynamic joint action. In four experiments, I employ a joint sequence production paradigm in which pairs of participants take turns producing tones to match a metronome pace. I use electroencephalography (EEG) to examine the time course of neural activity associated with each person’s actions (i.e., taps) and sensory consequences (i.e., tones) as the sequence unfolds. In Chapters 2 and 3 (Experiments 1 and 2), I investigate whether there is a perceptual differentiation in the processing of sensory consequences that result from one’s own vs. others’ actions by measuring auditory event-related potentials (ERPs) elicited by self- and partner-produced tones. Together, the findings from Experiments 1 and 2 indicate that self-specific attenuation of the auditory P2 provides a neural marker of self-other differentiation at a perceptual level. The findings from Experiment 2 also show that orienting processes associated with the coordination requirements of a joint action enhance P2 amplitude for partner-produced tones, suggesting that people direct their attention to their partner’s tone onsets to better coordinate with them. In Chapter 3 (Experiment 3 and 4), I investigate whether there is a differentiation in the motor activity that is associated with each person’s actions by conducting novel analyses of the data previously reported in Experiments 1 and 2 to examine motor-related cortical oscillations during self- and partner-produced taps. Together, the findings from Experiments 3 and 4 indicate that motor-related suppression provides a neural marker of self-other differentiation at a motor level. The findings from Experiment 3 and 4 also show that the coordination requirements of a joint action affect the degree of motor-related suppression for a partner’s actions, suggesting that people simulate their partners action timing to better coordinate with them. Overall, this research suggests that distinct neural activity for one’s own contributions to a joint action is dynamically coupled with periods of neural activity that reflect the integration of a partner’s actions based on the coordination demands of the joint action. Together, the experiments presented in this dissertation provide important and direct implications for theoretical accounts of joint action, as they further our understanding of how people maintain a distinction between their own and their partners’ contributions to a joint action, while also dynamically integrating information about the timing of their partners’ actions and sensory consequences to better coordinate with them. More broadly, these experiments contribute to our understanding of disorders associated with self-other processing deficits, such as schizophrenia, and provide valuable insight into the development of effective paradigms for motor training and rehabilitation
