After having delineated a deflationary neurobiologically-grounded account of basic aspects of intersubjectivity, namely an account focused on the minimal core mechanisms of intersubjectivity, let us now address the relationship between body and self. A minimal manifestation of the sense of self can already be identified in our first bodily experiences, and this highlights the potential contribution of bodily experiences to its constitution. Some aspects of the minimal self proposed by contemporary philosophical and empirical research are the notion of first-person perspective, the “mineness” of the phenomenal field (Meinigkeit), embodiment of point of view, and issues of agency and body ownership (Cermolacce et al. 2007).[12] On the philosophical side, phenomenology emphasizes the necessity of embodiment of the self for all the above-cited aspects of self experience. As argued by Cermolacce et al. (2007, p. 704, footnote 3), in phenomenology
the field of experience is not yet considered to be subjective because this predicate already implies that there is a subject. For phenomenology, the very idea of the subject articulates itself in experience. In this sense, the manifestation and appearing of experience are the conditions for the experience of the subject in question.
This philosophical standpoint has important implications for the empirical investigation of the neural correlates of the self.[13] Rather than empirically addressing the self by starting with a search for the neural correlates of a pre-defined, explicit, and reflective self-consciousness, we believe it to be more productive to investigate what what set of constitutive conditions allows an implicit and pre-reflective sense of self to emerge, and how this is effected. The interesting questions to be first answered are: “What enables the basic experience of ourselves as bodily selves? What enables us to implicitly distinguish ourselves, as bodily selves, from other human bodily selves?” In the following we review and discuss recent empirical evidence providing preliminary answers to these questions.
The relationship between the minimal sense of self and the cortical motor system was recently revealed. The motor experience of one’s own body, even at a covert level, allows an implicit and pre-reflective bodily self-knowledge to emerge, leading to a self/other distinction. Indeed it was recently shown that in a task in which differently rotated static pictures of right and left human hands were presented, participants who had to determine whether each observed hand was the right or the left one produced faster responses when observing the pictures of their dominant hand with respect to others’ hands (Ferri et al. 2011). However, when participants were asked to explicitly discriminate between their hands and the hands of others, the self-advantage disappeared. Implicit and explicit recognition of the bodily self dissociated: only implicit recognition of the bodily self, mapped in motor terms, facilitated implicit bodily self-processing.
A subsequent fMRI study by Ferri et al. (2012), using a similar hand mental rotation task, demonstrated that a bilateral cortical network formed by the supplementary and pre-supplementary motor areas, the anterior insula, and the occipital cortex was activated during processing of participants’ own hands. Furthermore, the contralateral ventral premotor cortex was uniquely and specifically activated during mental rotation of the participants’ own dominant hands. The ventral premotor cortex might represent one of the essential anatomo-functional bases for the motor aspect of bodily selfhood, also in light of its role in integrating self-related multisensory information. This hypothesis is corroborated by clinical and functional evidence showing its systematic involvement with body awareness (Ehrsson et al. 2004; Berti et al. 2005; Arzy et al. 2006). This evidence demonstrates a tight relationship between the bodily self-related multimodal integration carried out by the cortical motor areas, specifying the motor potentialities of one’s body and guiding its motor behaviour, and the implicit awareness one entertains of one’s body as one’s own body and of one’s behaviour as one’s own behaviour. Because the ventral premotor cortex is anatomically connected to visual and somatosensory areas in the posterior parietal cortex and to frontal motor areas we hypothesize that premotor cortex activity, by underpinning the detection of congruent multisensory signals from one’s own body, could be at the origin of the experience of owning one’s own body parts.
This minimal notion of the self, namely the bodily self as power-for-action (see Gallese & Sinigaglia 2010, 2011a), tacitly presupposes ownership of an action-capable agentive entity; hence it primarily rests upon the functionality of the motor system. As we just saw, empirical evidence supports the neural realization of this implicit aspect of selfhood in the brain’s motor cortex. Since the minimal bodily self rests neurally on the motor system, it logically follows that characteristics of the latter are defining for the former. This implies that one could attribute to the minimal bodily self known features of the motor system, including its capacities and limitations. The motor aspects of the bodily self provide the means to integrate self-related multimodal sensory information about the body and the world with which it interacts. This is also important from a theoretical point of view, because it opens the possibility of linking the openness of the self to the world to the motor potentialities its bodily nature entails.
One could then posit that the minimal bodily self when conceived in terms of its motor potentialities has a dual function. On the one hand, it constitutes important aspects of the basic sense of self. On the other, it shapes our perception and pre-reflective conception of others as other selves incarnated in a motorly-capable physical body with capacities and experiences similar to ours. Through mirror mechanisms and embodied simulation, others appear to us as second selves, or second persons. We believe that this perspective provides a more vivid experience of intersubjectivity, relative to the detached, propositional deliberation on the experiences of others available in standard mind reading of others.