Abstract
In the rubber-hand illusion, the sight of brushing of a rubber hand
at the same time as brushing of the persons own hidden hand is
sufficient to produce a feeling of ownership of the fake hand. We
shown previously that this illusion is associated with activity in
the
multisensory areas, most notably the ventral premotor cortex (Ehrsson
et al., 2004). However, it remains to be demonstrated that this
illusion does not simply reflect the dominant role of vision and that
the premotor activity does not reflect a visual representation of
an
object near the hand. To address these issues, we introduce a somatic
rubber-hand illusion. The experimenter moved the blindfolded
participants left index finger so that it touched the fake hand,
and simultaneously, he touched the participants real right hand,
synchronizing
the touches as perfectly as possible. After9.7 s, this stimulation
elicited an illusion that one was touching ones own hand. We
scanned brain activity during this illusion and two control conditions,
using functional magnetic resonance imaging. Activity in the
ventral premotor cortices, intraparietal cortices, and the cerebellum
was associated with the illusion of touching ones own hand.
Furthermore, the rated strength of the illusion correlated with the
degree of premotor and cerebellar activity. This finding suggests
that
the activity in these areas reflects the detection of congruent multisensory
signals from ones own body, rather than of visual representations.
We propose that this could be the mechanism for the feeling of body
ownership.
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