My body in the brain: A neurocognitive model of body-ownership
Section snippets
Experimenting with body-ownership
At the inaugural lecture of the Centre for Subjectivity Research (Copenhagen, Denmark), Waldenfels referred to the riddle of “how to justify the fact that a certain physical body is called my own body (corpus meum) and how to find out whether there are other bodies that are animated by other minds” (Waldenfels, 2004, p. 235). In essence, the riddle mentioned by Waldenfels refers to the foundations of the experience of one's own body: “What grounds my experience of my body as my own? The body
What is the experience of body-ownership like?
A large sample study (Longo et al., 2008) investigated the subjective experience during the RHI by asking participants to complete a 27-item questionnaire after each of the synchronous and asynchronous blocks of visuo-tactile stimulation. A Principal Component Analysis (PCA) revealed that the subjective experience of ownership of the rubber hand consists of distinct dissociable components present in both synchronous and asynchronous conditions (Longo et al., 2008): ownership (e.g. rubber hand
The bottom-up account of body-ownership: the role of intermodal matching
Why and how is the rubber hand experienced as part of one's body? In brief, the RHI reflects the malleability of the representation of the body caused by multisensory processing. Multisensory processing aims at the integration of sensory signals and the resolution of potential conflicts to generate a coherent representation of the world and the body. The RHI reflects a three-way weighted interaction between vision, touch, and proprioception: vision of tactile stimulation on the rubber hand
On corporal and non-corporeal objects
If body-ownership was driven by synchronous multisensory stimulation as a sufficient condition, then we would expect to induce a sense of body-ownership over objects that do not resemble body-parts. Accumulating evidence suggests that the RHI is not induced when the rubber hand is replaced by a neutral non-corporeal object such a wooden stick (i.e. coding of visual form representations of body-parts, Haans et al., 2008, Tsakiris et al., 2008, Tsakiris and Haggard, 2005, see also Holmes,
Body-ownership as an interaction between current multisensory input and internal models of the body: a neurocognitive model of body-ownership
Makin, Holmes, and Ehrsson (2008) put forward a parsimonious account of the RHI based on processes of multisensory integration in peri-hand space (Maravita, Spence, & Driver, 2003), without the need of top-down modulation by body-representations. On their account, the RHI occurs when the following two conditions are met: first, the rubber hand should be situated in an anatomically plausible position, and second, the synchronous visual and tactile events should be both located near to the
Testing for fit with the body-model: the contribution of rTPJ
How does the brain decide on the compatibility and eventual incorporeability of an external object? The behavioural (Tsakiris & Haggard, 2005) and electrophysiological (Press et al., 2008) data suggest that the process of filtering what may or may not become part of one's body is not the same as the process of multisensory integration that drives the RHI. Tsakiris et al. (2008) suggested that current sensory stimuli are processed and finally tested-for-fit against an abstract body-model that
Beyond my hand: my body and myself
This paper focused on the necessary conditions for the experience of a body-part as belonging to my body as studied with the RHI. Blanke and Metzinger (2009) rightly comment on the need to investigate a more “global” sense of body-ownership for the whole body. Three recent studies employed visuo-tactile synchrony to investigate the extent to which phenomena similar to the RHI can be induced for whole bodies. Ehrsson (2007) used synchronous or asynchronous visuo-tactile stimulation while
Conclusion
One of the key questions in the neurocognitive study of self is that of specificity (Gillihan and Farah, 2005, Legrand and Ruby, 2009). Gillihan and Farah (2005) point to the fact that there is not a self-specific neural system or a single sense of self. Legrand and Ruby (2009) suggest that “self-specificity characterizes the subjective perspective, which is not intrinsically self-evaluative but rather relates any represented object to the representing subject”, by means of multisensory
Acknowledgment
The author acknowledges the ESRC First Grant RES-061-25-0233 and the contribution of the European Science Foundation EUROCORES Programme CNCC, supported by funds from the EC Sixth Framework Programme under Contract no. ERAS-CT-2003-980409.
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