Brain Trickery, Body Ownership and the Sense of Self Gone Awry

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Image by Coscurro of RGB Stock

Neuroscientists at the Sackler Centre for Consciousness Science have created a virtual reality version of the classic ‘rubber hand illusion’ to explore consciousness and body trickery.

A virtual-reality hand, set to pulse in time with a heart beat, created the illusion of body ownership with the brain ‘accepting’ the virtual hand as part of its own body.

Easily hoodwinked, the brain was first proved to accept a foreign hand as its own in 1999 in the now classic rubber hand illusion.

The trick involves an inflated washing-up glove and a feather. With the participant’s real hand out of sight and only sensory stimuli to go by, the brain perceives the rubber hand as it’s own when stroked at the same time as the real hand. 

Virtual rubber hand

Dr. Keisuke Suzuki and Professor Anil Seth took the rubber hand trick to a virtual level to further explored the foundations of proprioception – the cocktail of sense, touch and brain signals which create the experience of being in the body, the very foundation of self consciousness.

Adding a cardio element as well as a virtual aspect, 21 volunteers participated in the study:

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    Head mounted display flickr photo by pestoverde shared under a Creative Commons (BY) license

    A virtual-reality, cardio-visual version of the participants own hands was projected onto a screen in front of them

  • Their real hand was hidden from view and attention drawn instead to the cardio-visual hand
  • The cardio-virtual hand pulsed from red to black in time with the participant’s own heartbeat.

Results showed that participants experienced the virtual hand as part of their body more frequently when the pulse was synchronized with their own heartbeat, compared to when the pulses were out of sync.

The brain was found to incorporate its impression of the body externally into its internal impression when trying to determine what was happening to the body.

The study also showed that the accurate visual feedback of intentional hand movements provides a powerful prompt for the experience of body ownership that can surpass even the influence of cardio-visual feedback.

The findings, published in Neuropsychologia, could lead to developments in the treatment of anxiety and body image disorders.

Prof. Anil Seth:

The findings tie in with our research at the Sackler Centre showing that many other perceptual and cognitive processes can be affected by the beating of the heart in ways that have important implications for clinical conditions such as anxiety and disorders of body image.

Our results showed that the illusional experience of the body is associated with the individual interoceptive sensitivity (sensitivity to stimuli originating inside of the body).  Although this sensitivity is not easy to be trained, it was reported that meditation possibly changes the interoceptive representation in our brain. As used in this study, experiencing the own heartbeat in visually salient ways might influence people’s interoceptive perception, which may help the anxiety disorder patients caused by the low interoceptive sensitivity.

Notes

Press Release: Sussex University, Sackler Centre for Consciousness Science

Create your own “rubber hand” illusion (New Scientist)

Proprioceptive drift without illusions of ownership for rotated hands in the “rubber hand illusion” paradigm.

 

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