CardiovascularPerceiving Touch And Your Self Outside Of Your Body: Altering Bodily Self-Consciousness And Touch Perception Via The Full Body Illusion
When you feel you are being touched, usually someone or something is
physically touching you and you perceive that your "self" is located in
the
same place as your body. In new research published in the open-access,
peer-reviewed journal PLoS ONE, neuroscientists at the Ecole Polytechnique
Fçİdçİrale de Lausanne (EPFL), Switzerland, investigated the relationship
between bodily self-consciousness and the way touch stimuli are spatially
represented in humans. They found that sensations of touch can be felt and
mislocalised towards where a "virtual" body is seen. These findings
will provide new avenues for the animation of virtual worlds and machines.
In their previous research, Professor Olaf Blanke"s lab at the EPFL found
that the consciousness of one"s own body (the sense of
self-identification and self-location) can be altered in healthy people
under certain experimental conditions, yielding similar sensations to
those
felt in out-of-body experiences. In this new study, Aspell and colleagues
in Blanke"s lab used a crossmodal congruency task to determine whether
there is a change in touch perception during this illusion.
A number of earlier studies showed that if a rubber hand is positioned
such that it extends from a person"s arm while her actual hand is hidden
from
view, and both her real hand and the rubber hand are stroked at the same
time, she seems to feel the touch in the location where she sees the
rubber
hand being touched. This effect and the experienced "ownership" of the
rubber hand is the "rubber hand illusion."
Aspell, a postdoctoral researcher, along with graduate student Bigna
Lenggenhager and Professor Olaf Blanke sought to expand on this research
to see
whether there are changes in touch perception when humans experience
ownership of a whole virtual body. They designed a novel behavioural task
in
which the experimental participants had to try to detect where on their
body vibrations were occurring. At the same time, they viewed their own
body
via a head-mounted display connected to a camera filming the participant"s
back from two metres away. The participants had to ignore light flashes
that appeared on their body near the vibrators. To induce the feeling that
they were located in the position where they viewed their body (i.e. two
metres in front of them), participants were stroked on their backs with a
stick. This induced a "full body illusion" in which a person perceives
herself as being located outside the confines of her own body.
By measuring how strongly the light flashes interfered with the perception
of the vibrations, the researchers were able to show that the mapping of
touch sensations was altered during the full body illusion. The mapping of
touch in space was shifted towards the virtual body when subjects felt
themselves to be located where the virtual body was seen.
This study demonstrates that changes in self-consciousness ("where am I
located?" and "what is my body?") are accompanied by changes in where
touch sensations are experienced in space. Importantly, these data reveal
that brain mechanisms of multisensory processing are crucial for the "I"
of conscious experience and can be scientifically manipulated in order to
animate and incarnate virtual humans, robots, and machines.
Funding:
This work was supported by the Swiss National Science Foundation
(#3100-067874.02). The funders had no role in study design, data
collection
and analysis, decision to publish, or preparation of the manuscript.
Competing Interests:
The authors have declared that no competing interests
exist.
Citation:
Aspell JE, Lenggenhager B, Blanke O (2009)
"Keeping in Touch with One"s Self: Multisensory Mechanisms of Self-Consciousness."
PLoS ONE 4(8):e6488.doi: 10.1371/journal.pone.0006488
PLoS ONE