Australian researchers have shown that along with the sense of touch and vision, signalling receptors in the muscles and joints also play a critical role. The finding, published recently in the Journal of Physiology, will help in designing treatments for disorders of body ownership that can occur with conditions such as stroke and epilepsy.
Lead author Lee Walsh, of Neuroscience Research Australia, explained we instinctively know our body parts "belong" to us. However, how the brain develops that map of what belongs to it is still in part unknown.
"How do I know my hand is mine and not yours and that the telephone is not a part of my body," he said.
Previous research shows people can be deluded into claiming ownership of an artificial hand. This is done by simultaneously stroking the subject's hidden hand and a visible artificial rubber hand.
"Once the illusion of ownership of the hand is established, subjects have physiological responses to threats made against the rubber hand," Walsh and his colleagues wrote in the paper.
In this study the team was interested to see if other sensory channels could also be important in developing body ownership.
"We can use vision to see parts of the body, but we can also see other bodies, so vision alone cannot differentiate foreign body parts from those we own," Walsh said. "Muscle receptors can only signal things that are happening to the body so would seem to be an ideal candidate to signal ownership."
To test this theory, the team induced an illusion of ownership over a plastic index finger. The finger was used because it is feasible to block the sense of touch with local anaesthetic. The team found the sense of ownership still occurred when participants' fingers were anaesthetized. Walsh said the results show visual-tactile cues are not critical in establishing body ownership. Instead muscle-related signals coupled with vision are sufficient for the brain to recognize ownership.
Read more at Discovery News
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