Multisensory Perception and Bodily Self-Consciousness: From Out-of-Body to Inside-Body Experience

Excerpt

Despite the apparent unitary, global character of bodily self-consciousness, experimental manipulations have mainly focused on subglobal aspects, such as the sense of ownership and agency for one’s hand and its movements (Botvinick and Cohen 1998; Ehrsson et al. 2004; Jeannerod 2006, 2007; Knoblich 2002; Pavani et al. 2000; Tsakiris and Haggard 2005; Tsakiris et al. 2007). These latter studies on body-part representation are important (and will be discussed below in detail), yet we have argued (e.g., see Blanke and Metzinger 2009) that they fail to account for a key feature of bodily self-consciousness: its global character. This is because a fundamental aspect of bodily self-consciousness is its association with a single, whole body, not with multiple body parts (Blanke and Metzinger 2009; Carruthers 2008; Lenggenhager et al. 2007; Metzinger et al. 2007). A number of recent studies (Aspell et al. 2009; Ehrsson 2007; Lenggenhager et al. 2007, 2009; Mizumoto and Ishikawa 2005; Petkova and Ehrsson 2008) have demonstrated that more global aspects of body perception can also be experimentally manipulated using multisensory conflicts. These experimental studies on healthy subjects were inspired by an unusual and revealing set of neurological phenomena—autoscopic phenomena—in which the sense of the body as a whole is disrupted in different ways, and which are likely to be caused by an underlying abnormality in the multisensory integration of global bodily inputs (Blanke and Mohr 2005). In this chapter, we first examine how the scientific understanding of bodily self-consciousness and its multisensory mechanisms can be informed by the study of autoscopic phenomena. We then present a review of investigations of multisensory processing relating to body-part perception (“rubber hand” illusion studies: Botvinick and Cohen 1998; Ehrsson et al. 2004; Tsakiris and Haggard 2005) and go on to discuss more recent “full body” illusion studies that were inspired by autoscopic phenomena and have shown that it is also possible to dissociate certain components of bodily self-consciousness—namely, self-location, self-identification, and the first-person perspective—in healthy subjects by inducing multisensory conflicts.