Neural correlates of the distinction between self and others in the macaque's frontal cortex

Social interaction is a fundamental prerogative of primate’s life. Different abilities are part of the repertoire that is necessary to fulfill a complex social behavior. Many of these abilities are shared between human and monkeys: non-human primates are capable of cooperating (Haroush & Williams 2015), monitor each other’s actions (Falcone et al. 2012a), learn from observation (Subiaul et al. 2004, Falcone et al. 2012b, Chang et al. 2011, Monfardini et al. 2014). One of the bases of social behavior is certainly the ability to understand other’s actions. In this respect, one of the major discovery in neurophysiology in the last decades is that of ‘mirror neurons’ in monkey’s parietofrontal circuits (di Pellegrino et al. 1992, Rizzolatti et al. 1996). These neurons are activated both when an action is performed and when the same action it is just observed. It has been suggested that they could play a critical role in providing the bases for understanding the action of others through the same neural mechanisms which activate during the execution of a specific motor act. Despite that, the activity of mirror neurons is not able to provide a neural signal able to distinguish between self and others. Recently, some studies attempted to investigate the neural correlates of self-others differentiation, looking for evidence of a non-overlapping neural representation of self and others action. In this thesis, I will discuss the results of three distinct neurophysiology experiments that investigated the role played by different areas of the macaque frontal cortex in providing such distinction. Through a task design that required the interaction between humans and monkeys, the aim of these experiments was to explore the distinct neural correlates which allow the prediction or the anticipation of someone else actions. In Section 1, a general description of the experimental design adopted by the three experiments discussed here is provided. The non-match-to-goal task required the interaction between the monkey and the experimenter, which alternated their role as actor and observer along the different trials. In Section 2, the methods and the main results of two previous neurophysiology experiments (Falcone et al. 2016, Falcone et al. 2017) are discussed. These experiments investigated the property of single neurons recorded in the lateral prefrontal cortex and in the medial frontal cortex. In Section 3 are discussed the methods and the main results of our study (Cirillo et al. 2018), which adopted the same task design as the two previous experiments, recording the activity of neurons in the dorsal premotor cortex. Section 4 presents an overview of the overall results, discussing the role played by different categories of cells identified within the frontal cortex in the three experiments that investigated the neural correlates of representing others’ future and past behavior in a separate way from one’s own.