Saturday, February 18, 2012

Multi-Sensory and Sensorimotor Foundation of Bodily Self-Consciousness – An Interdisciplinary Approach

Cool and geeky neuroscience paper on body-consciousness. The authors review behavioral, brain imaging, and clinical evidence about three aspects of bodily self-consciousness: self-location, first-person perspective, and self-identification.

Multi-sensory and sensorimotor foundation of bodily self-consciousness – an interdisciplinary approach

  • 1 Laboratory of Cognitive Neuroscience, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
  • 2 Rehabilitation Engineering Laboratory, Eidgenössische Technische Hochschule Zürich, Zurich, Switzerland
  • 3 Department of Neurology, University Hospital, Geneva, Switzerland

Scientific investigations on the nature of the self have so far focused on high-level mechanisms. Recent evidence, however, suggests that low-level bottom-up mechanisms of multi-sensory integration play a fundamental role in encoding specific components of bodily self-consciousness, such as self-location and first-person perspective (Blanke and Metzinger, 2009). Self-location and first-person perspective are abnormal in neurological patients suffering from out-of-body experiences (Blanke et al., 2004), and can be manipulated experimentally in healthy subjects by imposing multi-sensory conflicts (Lenggenhager et al., 2009). Activity of the temporo-parietal junction (TPJ) reflects experimentally induced changes in self-location and first-person perspective (Ionta et al., 2011), and dysfunctions in TPJ are causally associated with out-of-body experiences (Blanke et al., 2002). We argue that TPJ is one of the key areas for multi-sensory integration of bodily self-consciousness, that its levels of activity reflect the experience of the conscious “I” as embodied and localized within bodily space, and that these mechanisms can be systematically investigated using state of the art technologies such as robotics, virtual reality, and non-invasive neuroimaging.

Citation: Ionta, S., Gassert, R. & Blanke, O. (2011) Multi-sensory and sensorimotor foundation of bodily self-consciousness – an interdisciplinary approach. Frontiers in Perception Science, 2:383. doi: 10.3389/fpsyg.2011.00383

Bodily Self

Some of the most important brain systems of humans are dedicated to the maintenance of the balance between the self and the external environment, by processing and integrating many different bodily sensory inputs (visual, auditory, vestibular, somatosensory, motor, visceral, etc.), and providing an online representation of the body in the world (Damasio, 1999; Gallagher, 2005; Jeannerod, 2006; Blanke and Metzinger, 2009). In this view, the body representation in the brain is a complex crossroad where multi-sensory information is compounded in order to build the basis for bodily self-consciousness (Haggard et al., 2003; Jeannerod, 2007; Metzinger, 2008). Many behavioral studies over the last two decades have used techniques imposing multi-sensory conflict as a means to manipulate some components of self-consciousness. For example, the “rubber hand illusion” paradigm showed that by manipulating local aspects of body perception, it is possible to induce an illusory sense of ownership of a fake hand (e.g., Botvinick and Cohen, 1998; Pavani et al., 2000; Ehrsson et al., 2004; Tsakiris and Haggard, 2005; Tsakiris et al., 2007; Aimola Davies et al., 2010). In particular, if participants observe a rubber hand being stroked synchronously with their own (hidden) hand, they tend to report self-attribution of the rubber hand, as if it was their own hand. This illusory self-attribution is often accompanied by a “proprioceptive drift” toward the location of the rubber hand. Specifically, participants report a change in where they feel their real hand to be located (review in Tsakiris, 2010). Similarly, if a participant holds one palm against that of someone else and simultaneously strokes the dorsal side of both her/his own and the other’s index finger, an illusory feeling of numbness for the other person’s finger can be perceived: the so-called “numbness” illusion (Dieguez et al., 2009). Furthermore, it has recently been shown that illusory self-attribution is not limited to the hands, but extends to other body parts including the face (Sforza et al., 2010). For example, the experience of having one’s own face touched whilst simultaneously (the spatial and temporal sense) seeing the same action applied to the face of another, elicits the so-called “enfacement” illusion: that is an illusory sense of face ownership is induced and the other’s facial features are incorporated into the participant’s face (Sforza et al., 2010). All of these findings on illusory self-attribution support the idea that low-level multi-sensory processes can influence bodily self-consciousness. However, the self and bodily self-consciousness is globally associated with the body, rather than with multiple different body parts (Lenggenhager et al., 2007; Metzinger, 2008; Blanke and Metzinger, 2009). Recent behavioral studies showed that, beyond local aspects of body perception and self-attribution (rubber hand illusion, numbness illusion, face illusion), multi-sensory conflicts can also be used to manipulate more global aspects of body perception (Ehrsson, 2007; Lenggenhager et al., 2007, 2009; Petkova and Ehrsson, 2008; Aspell et al., 2009, 2010). These studies showed that it is possible to investigate more global aspects of bodily self-consciousness and described several different components thereof, such as self-location, first-person perspective, and self-identification.
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