In her impressive article, Susan Hurley offers the shared circuit model (SCM) as the common structure underlying perception and action, which, as such, can provide the foundation for the overlapping and shared dynamics between self and other. Without going into further details here, I comment on two important conceptual questions raised in Hurley's remarkable account. First, the SCM raises the question of the kind of neural coding that must be presupposed in order to make the SCM and its shared dynamic between perception and action possible. Second, the SCM raises the question of the characterization of the self that is supposed to be based upon the SCM.
The term code describes a mean or measurement that captures and reflects teleogically meaningful activity in a system; this mean or measurement is implemented in certain rules and mechanisms that guide and format the system's processing of various contents (see deCharms & Zador Reference deCharms and Zador2000; Friston Reference Friston1997). For instance, these rules and mechanisms may format and guide the neural processing of perceptual contents and action contents. Hurley's SCM, which assumes a shared dynamic and structure between action and perception, implies a common code for perception and action. Referring to the theory of event coding (TEC) by Hommel et al. (Reference Hommel, Musseler, Aschersleben and Prinz2001), Hurley mentions that there might be common coding between action and perception; but she does not elaborate on it in further detail. The TEC (Hommel et al. Reference Hommel, Musseler, Aschersleben and Prinz2001) claims that perceived events (perception) and to-be-produced events (action) are equally represented by integrated networks and so-called event files (Hommel Reference Hommel2004; see also Noë Reference Noë2004). What remains unclear, however, is the exact format (e.g., the formal structure) according to which these event files are coded.
Since these “event files” are supposed to be common to both action and perception, there can no longer be translation between the two for a couple of reasons. First, translation presupposes different formats (i.e., formal structures) between action and perception – or else, translation would not be needed. Second, a need for translation would imply that event files are not shared between perception and action. Accordingly, there must be a different kind of coding than what I call translational coding, in order to account for Hurley's SCM. How must incoming or outgoing stimuli be coded in order to allow for the SCM and the assumed common structure of perception and action? I suggest that rather than the stimuli themselves being coded, be they either perceptual or action related, it is the relation between different stimuli that is coded. That is, it is not the incoming stimulus of some perceived event that is coded in isolation but rather its relationship to actually generated motor stimuli and vice versa. Such a relationship can be coded only if translational coding is replaced by what I call relational coding (Northoff Reference Northoff2004). Relational coding assumes that the stimuli are formatted according to their relationship to other stimuli as, for instance, incoming sensory stimuli are set and coded in relation to outgoing motor stimuli, and vice versa.
Hurley suggests that the SCM provides the basis for constituting and distinguishing self and other. One would consequently assume that relational coding might also provide the format according to which self and other are coded. This implies not only that self and other are based upon the relation between perception and action but that our self is essentially a rather basic and relational function that is always already set in relation to others and the environment. Rather than attributing some special contents like higher-order cognitive contents to the self, this implies that the self may be considered some kind of specific format that allows for stimuli to be set in relation to each other, which in turn implicates relation of the stimuli to the respective organism and ultimately to the environment. Instead of considering the self as a special encapsulated entity or function, our self may then be essentially relational so that one may speak of a relational self. This would be well compatible with recent suggestions of self-related processing, which implicates a subcortical-cortical midline network (Northoff et al. Reference Northoff, Heinzel, de Greck, Bermpohl, Dobrowolny and Panksepp2006; in press). Self-related processing concerns stimuli that are experienced as strongly related to one's own person.
Without going deeply into abstract philosophical considerations, I would like to give a brief theoretical description of what I mean by the terms experience and strongly related, while to one's person is meant very simply as an organism. Experience refers to phenomenal experience such as, for example, the feeling of love or the smell of a rose. The term strongly related points out the process of associating and linking interoceptive and exteroceptive stimuli with a particular person. The main feature here is not the distinction between diverse sensory modalities, but rather, the linkage of the different stimuli to the individual person, that is, to his or her self. What unifies and categorizes stimuli in this regard is no longer their sensory origin but the strength of their relation to the self. The self-stimulus relation results in what has been called mineness; Lambie and Marcel (Reference Lambie and Marcel2002) speak of an “addition of the ‘for me’” by means of which that particular stimulus becomes “mine,” resulting in “mineness.”
In sum, I suggest that Hurley's assumption that the SCM provides the foundation for self and other presupposes (1) a different concept of the self that characterizes the self as format, relational, embodied, and embedded (see also Clark Reference Clark1997; Reference Clark1999); and (2) self-related processing rather than by specific contents, a special isolated entity or function, and higher-order cognitive processing. In other terms, Hurley's SCM provides a highly fruitful starting point for reconceptualizing our notion of self and to abandon philosophical and psychological substance-, entity-, or cognitive-based models of self – and, at the same time, for gaining some insight into the hitherto unknown mechanisms of neural coding.
