Neuroscientists create phantom sensations in non-amputees

April 11, 2013

The sensation of having a physical body is not as self-evident as one might think. Almost everyone who has had an arm or leg amputated experiences a phantom limb: a vivid sensation that the missing limb is still present. A new study by neuroscientists at the Karolinska Institutet in Sweden shows that it is possible to evoke the illusion of having a phantom hand in non-amputated individuals.

In an article in the scientific periodical Journal of Cognitive Neuroscience, the researchers describe a perceptual in which healthy experience having an invisible hand. The experiment involves the participant sitting at a table with their right arm hidden from their view behind a screen. To evoke the illusion, the scientist touches the right hand of the participant with a small paintbrush while imitating the exact movements with another paintbrush in mid-air within full view of the participant.

This video is not supported by your browser at this time.
Ph.D. Student Arvid Guterstam explains how he and his colleagues at Karolinska Institutet in Sweden can evoke the illusion of having a phantom hand in non-amputated individuals. Credit: Ola Danielsson, Karolinska Institutet

"We discovered that most participants, within less than a minute, transfer the of touch to the region of where they see the paintbrush move, and experience an invisible hand in that position," says Arvid Guterstam, lead author of the study. "Previous research has shown that non-bodily objects, such as a block of wood, cannot be experienced as one's own hand, so we were extremely surprised to find that the brain can accept an invisible hand as part of the body."

The study comprises eleven experiments that explore in detail the illusory experience and include 234 volunteers. To demonstrate that the illusion actually worked, the researchers would make a stabbing motion with a knife towards the empty space "occupied" by the invisible hand and measure the participant's response to the perceived threat. They found that the participants' stress responses were elevated while experiencing the illusion but absent when the illusion was broken. In another experiment, the volunteers were asked to close their eyes and quickly point with their left hand to their right hand (or to where they perceived it to be). After having experienced the illusion for a while, they would point to the location of the invisible hand rather than to their real hand.

The researchers also measured the brain activity of the participants using functional magnetic resonance imaging (fMRI). Perceiving the invisible hand illusion led to increased activity in the same parts of the brain that are normally active when individuals see their real hand being touched or when participants experience a prosthetic hand as their own.

"Taken together, our results show that the sight of a physical hand is remarkably unimportant to the brain for creating the experience of one's physical self," says Arvid Guterstam.

The researchers hope that the results of their study will offer insight into future research on phantom pain in amputees.

"This illusion suggests that the experience of phantom limbs is not unique to amputated individuals, but can easily be created in non-amputees," says the principal investigator, Dr. Henrik Ehrsson, docent at the Department of Neuroscience. "These results add to our understanding of how phantom sensations are produced by the brain, which can contribute to future research on alleviating phantom pain in amputees."

Explore further: Weight of object not an issue when determining left or right-handedness

More information: The invisible hand illusion: Multisensory integration leads to the embodiment of a discrete volume of empty space, Journal of Cognitive Neuroscience, 2013.

Related Stories

Recommended for you

New insights on how cocaine changes the brain

November 25, 2015

The burst of energy and hyperactivity that comes with a cocaine high is a rather accurate reflection of what's going on in the brain of its users, finds a study published November 25 in Cell Reports. Through experiments conducted ...

Can physical exercise enhance long-term memory?

November 25, 2015

Exercise can enhance the development of new brain cells in the adult brain, a process called adult neurogenesis. These newborn brain cells play an important role in learning and memory. A new study has determined that mice ...

Umbilical cells help eye's neurons connect

November 24, 2015

Cells isolated from human umbilical cord tissue have been shown to produce molecules that help retinal neurons from the eyes of rats grow, connect and survive, according to Duke University researchers working with Janssen ...

Brain connections predict how well you can pay attention

November 24, 2015

During a 1959 television appearance, Jack Kerouac was asked how long it took him to write his novel On The Road. His response – three weeks – amazed the interviewer and ignited an enduring myth that the book was composed ...

No cable spaghetti in the brain

November 24, 2015

Our brain is a mysterious machine. Billions of nerve cells are connected such that they store information as efficiently as books are stored in a well-organized library. To this date, many details remain unclear, for instance ...


Adjust slider to filter visible comments by rank

Display comments: newest first

Apr 11, 2013
This comment has been removed by a moderator.
1.5 / 5 (4) Apr 11, 2013
When the physical you are stimulated with light, sound, smell, taste, touch, thought, a separate sense of discriminatory awareness is at the back of all that, and interprets what the physical you are perceiving. This independent awareness is already well established by the time the physical you are ready to be born. For example, when something flashes at the corner of you eyes, the "physical you" knows there are info, but can't interpret and clarify them for the contents. Only when you "pay attention" i.e. the discriminatory awareness comes into play then you get the content. Thus the evidence for a independent discriminatory awareness is that "it" understands what "you" are perceiving. Put it another way: Who is thinking the "'I' know what/that I am thinking"? Who is thinking the "'I' know that I am trying not to think"? When there sis no sound, the sense of hearing is still always there. Similarly, its sense of limbs is always there, whether they are there or not.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.