Neuroscientists in the UK have discovered that a virtual-reality hand, which is synchronized to "pulse" in time to an individual's heartbeat, creates the illusion in the brain of "body ownership" - with the brain believing the hand is part of its own body.
The researchers, from the University of Sussex in England, say the findings may lead to new clinical developments in anxiety and body image disorders. The study was published in the journal Neuropsychologia.
Dr. Keisuke Suzuki and Prof. Anil Seth, of the Sackler Centre for Consciousness Science, led the study demonstrating how the brain constructs the experience of body ownership from visual and tactile sensory signals and body-related feedback.
They drew from the "rubber hand illusion," a classic body ownership trick occurring when a rubber hand is perceived as part of the body when stroked at the same time as a real hand.
The researchers from the University of Sussex, however, added a "cardio" element by implementing a unique combination of heartbeat monitoring and augmented reality, which created a "cardio-visual" version of the rubber hand illusion.
There were 21 volunteers who participated in the study, which included the following steps:
- Participants wore a head-mounted display to facilitate the augmented reality
- Researchers hid the participants' real hand from their visual field and drew attention instead to the cardio-visual hand
- A virtual-reality, cardio-visual version of the participants' own hands was projected onto a screen in front of them
- The cardio-virtual hand pulsed from red to black in synch with the participants' own heartbeats.
The cardio hand pulsed at both a synchronized and asyncronized rate to the participants' heartbeats.
Results showed that the participants experienced the virtual hand as part of their body more frequently when the pulses were synchronized with their actual heartbeat, compared with when the pulses were out of synch.
The researchers say the results show that the brain incorporates its impression of the body externally into its impression internally when determining what is actually happening to the body.
The experiment also showed that the accurate visual feedback of intentional hand movements provides a powerful prompt for the experience of body ownership that can surpass the influence of cardio-visual feedback.
Prof. Anil Seth says:
"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."
This study ties into other research co-developed by Prof. Seth involving the brain continuously trying to predict its own physiological and physical states.
A recent study revealed that our inner voice is actually the brain's prediction of how we sound.
Written by Sally Burr
See Sally's blog