How do you know your body is your own?

Researchers have discovered one more piece of the puzzle of how we create a sense of body ownership, allowing us to differentiate our own body from everything else around us.

The findings will help in designing clinical tests and treatments for people with disorders of body ownership, a common side-effect of diseases such as stroke.

The body ownership experiment
Which finger is mine?

“Some stroke patients can develop the feeling that their affected hand or arm no longer belongs to them. This makes rehabilitation and recovery difficult because they disregard the hand and do not use it,” says Dr Lee Walsh, from Neuroscience Research Australia.

“By understanding how the sense of body ownership is generated, we can develop new therapeutic approaches to help the thousands of people affected by stroke regain more complete use of their stroke-affected limbs.”

Our sense of body ownership tells us that our body belongs to us, and that other bodies do not.

Previous research, involving an illusion of ownership over a rubber hand, has shown that this sense body ownership is generated in part using touch and vision.

Like the skin receptors used for touch, sensory receptors in the muscles also provide information about events occurring to the body. It has not been clear, however, whether muscle receptors are also involved in generating our sense of body ownership.

In this study, researchers induced an illusion of ownership over a plastic finger using movement, which excites muscle receptors.

The sense of ownership still occurred when participants’ fingers were anaesthetised, blocking any contribution from skin (touch) and joint receptors.

“The results clearly show that muscle receptors contribute to the sense of body ownership,” says Dr Walsh.

“This is the first study to show that the brain uses information from muscles to tell us what is our body and what isn’t. This is fundamental to identifying how the brain and body interact to give us a sense of self,” says Dr Walsh.

The study was published in the Journal of Physiology. [Pubmed link]

Read ‘Muscling in on body-ownership mystery‘ at ABC Science

Read ‘Muscles play a part in the rubber hand illusion‘ at New Scientist