Searching for an integrated self-representationRecent inquiries into the nature of self-representation have put forward a new and interesting conceptualization of the self, as a “center of gravity” of one's private and social behavior. We review recent neuroimaging work that has suggested interactions among brain regions comprising the default state network, including medial and temporo-parietal cortical regions and the mirror neuron system including lateral fronto-parietal regions as two interacting neural systems that work in concert to produce a cohesive self-representation through simulation. Simulation processes—broadly construed here as using existing representations as templates for understanding novel information—are instantiated by these brain systems across a wide range of domains including time, space, physical and social, giving rise to the multifaceted Self that we all are. Accumulating evidence also suggests, that these simulation processes are used in a multitude of cognitions that constitute the self, including autobiographical memory and prospection, perspective taking, understanding other's actions and mental states and embodied self-representation.
Based on the property of mirror neurons to internally simulate actions performed by others, it has been proposed that the MNS may provide the link between the physical representation of the Self as related to the physical representation of others.7,38,39 In fact, the MNS and the default network show opposing patterns of activation during the process of self-other distinction, such that mirror regions show increased activity to “self” relative to “other,” while default network regions deactivate less to “other” relative to “self.”38
We have attempted to outline a common thread linking aspects of the self across the domains of time, space, physical embodiment and the social world as may be accomplished through a simulation mechanism. In our interpretation of the process of simulation, the self uses available knowledge as a template for processing, representing and understanding new information. Whether simulation involves self-projection in time for the purposes of planning the future, or projection of a perceived image onto the self-image during self-other differentiation; at their core, mental time travel, perspective taking, self-representation and mentalizing are all cogitations that in the broadest sense appear to involve a simulation mechanism. These high-level functions rely on a distributed network of brain structures, including the medial prefrontal cortex, medial temporal lobe, parietal regions and the temporo-parietal junction forming the core of the default mode network, and the posterior inferior frontal gyrus and inferior parietal lobule forming the core of the human mirror neuron system.