(Press-News.org) How we experience our own bodies is a classical question in psychology and neuroscience. It has long been believed that our body image is limited by our innate body plan – in other words that we cannot experience having more than one head, two arms and two legs. However, brain scientists at the Swedish medical university Karolinska Institutet have now shown that it is possible to make healthy volunteers experience having three arms at the same time.
In a novel paper published in the online scientific journal PLoS ONE they describe how it is possible to create an illusion of owning three arms, under controlled conditions in a laboratory. The experiment involves the participant sitting at a table and having a realistic prosthetic arm placed next to their right arm. The subject then sees her two real arms and the extra prosthetic arm, made out of rubber. To produce the feeling of owning the rubber arm, the scientist touches the subject's right hand and the rubber hand with two small brushes at corresponding location – synchronizing the strokes as perfectly as possible.
"What happens then is that a conflict arises in the brain concerning which of the right hands belongs to the participant's body", says Arvid Guterstam, one of the scientists behind the study. "What one could expect is that only one of the hands is experienced as one's own, presumably the real arm. But what we found, surprisingly, is that the brain solves this conflict by accepting both right hands as part of the body image, and the subjects experience having an extra third arm."
The study consists of a series of experiments; in total 154 healthy volunteers were tested.
To prove that the prosthetic arm was truly experienced as a third arm, the scientist 'threatened' either the prosthetic hand or the real hand with a kitchen knife, and measuring the degree of sweating of the palm as a physiological response to this provocation. The results demonstrated that the subjects had the same stress response when the prosthetic hand was threatened as when the real hand was, but only during the periods when they experienced the third arm illusion. For instance, there was no stress reaction when the prosthetic right arm was replaced with a left arm or a prosthetic foot.
The results of the study may benefit patients by creating new applications in prosthetics research.
"It may be possible in the future to offer a stroke patient, who has become paralysed on one side of the body, a prosthetic arm that can be used and experienced as his own, while the paralysed arm remains within the patient's body image", says Henrik Ehrsson, who has led the study at the Department of Neuroscience. "It is also conceivable that people with demanding work situations could benefit of an extra arm, such as firemen during rescue operations, or paramedics in the field".
###
Citation: Guterstam A, Petkova VI, Ehrsson HH (2011) The Illusion of Owning a Third Arm. PLoS ONE 6(2): e17208. doi:10.1371/journal.pone.0017208
Funding: This study was funded by the European Research Council (erc.europa.eu), The Swedish Foundation for Strategic Research (www.stratresearch.se/en),
The Human Frontier Science Program (www.hfsp.org), and Stockholm Brain Institute (www.stockholmbrain.se). The funders had no role in study design, data
collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
Scientists create illusion of having 3 arms
2011-02-24
ELSE PRESS RELEASES FROM THIS DATE:
Lasers ID deadly skin cancer better than doctors
2011-02-24
DURHAM, N.C. – High-resolution images from a laser-based tool developed at Duke University could help doctors better diagnose melanoma, the deadliest form of skin cancer, while potentially saving thousands of lives and millions of dollars in unnecessary healthcare costs each year.
The tool probes skin cells using two lasers to pump small amounts of energy, less than that of a laser pointer, into a suspicious mole. Scientists analyze the way the energy redistributes in the skin cells to pinpoint the microscopic locations of different skin pigments.
For the first time, ...
Hyperactive nerve cells may contribute to depression
2011-02-24
UPTON, NY - Scientists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory, Cold Spring Harbor Laboratory, and the University of California, San Diego School of Medicine, have identified hyperactive cells in a tiny brain structure that may play an important role in depression. The study, conducted in rats and appearing in the February 24, 2011, issue of Nature, is helping to reveal a cellular mechanism for depressive disorders that could lead to new, effective treatments.
The research provides evidence that inhibition of this particular brain region ...
Aging, interrupted
2011-02-24
VIDEO:
Salk scientist Dr. Belmonte discusses the research.
Click here for more information.
LA JOLLA, CA—The current pace of population aging is without parallel in human history but surprisingly little is known about the human aging process, because lifespans of eight decades or more make it difficult to study. Now, researchers at the Salk Institute for Biological Studies have replicated premature aging in the lab, allowing them to study aging-related disease in a dish.
In ...
New biological pathway identified for post-traumatic stress disorder
2011-02-24
High blood levels of a hormone produced in response to stress are linked to post-traumatic stress disorder in women but not men, a study from researchers at Emory University and the University of Vermont has found.
The results are scheduled for publication in the Feb. 24 issue of Nature.
The hormone, called PACAP (pituitary adenylate cyclase-activating polypeptide), is known to act throughout the body and the brain, modulating central nervous system activity, metabolism, blood pressure, pain sensitivity and immune function. The identification of PACAP as an indicator ...
New 'thunder-thighs' dinosaur discovered
2011-02-24
LONDON – A new dinosaur named Brontomerus mcintoshi, or "thunder-thighs" after its enormously powerful thigh muscles, has been discovered in Utah, USA. The new species is described in a paper recently published in the journal Acta Palaeontologica Polonica by an international team of scientists from the U.K. and the U.S.
A member of the long-necked sauropod group of dinosaurs which includes Diplodocus and Brachiosaurus, Brontomerus may have used its powerful thighs as a weapon to kick predators, or to help travel over rough, hilly terrain. Brontomerus lived about 110 ...
Quantum hot potato: NIST researchers entice 2 atoms to swap smallest energy units
2011-02-24
BOULDER, Colo.—Physicists at the National
Institute of Standards and Technology
(NIST) have for the first time coaxed two
atoms in separate locations to take turns
jiggling back and forth while swapping the
smallest measurable units of energy. By
directly linking the motions of two physically
separated atoms, the technique has the
potential to simplify information processing in
future quantum computers and simulations.
Described in a paper published Feb.
23 by Nature,* the NIST experiments enticed two beryllium ions (electrically charged
atoms) to take turns ...
Virus-mimicking nanoparticles can stimulate long lasting immunity
2011-02-24
Vaccine scientists say their “Holy Grail” is to stimulate immunity that lasts for a lifetime. Live viral vaccines such as the smallpox or yellow fever vaccines provide immune protection that lasts several decades, but despite their success, scientists have remained in the dark as to how they induce such long lasting immunity.
Scientists at the Emory Vaccine Center have designed tiny nanoparticles that resemble viruses in size and immunological composition and that induce lifelong immunity in mice. They designed the particles to mimic the immune‑stimulating effects ...
Quantum computer -- tune in now
2011-02-24
The Austrian research group led by physicist Rainer Blatt suggests a fundamentally novel architecture for quantum computation. They have experimentally demonstrated quantum antennae, which enable the exchange of quantum information between two separate memory cells located on a computer chip. This offers new opportunities to build practical quantum computers. The researchers have published their work in the scientific journal Nature.
Six years ago scientists at the University of Innsbruck realized the first quantum byte – a quantum computer with eight entangled quantum ...
Microbes help children to breathe easily
2011-02-24
The incidence of asthma among children in Europe continues to rise. But not all children are equally at risk. Several studies published over the past few years have shown that children living on farms are significantly less likely to develop asthma than others. An international team of researchers including Dr. Markus Ege and Professor Erika von Mutius of Children's Surgical Clinic in the Dr. von Hauner Children's Hospital (Medical Center of the University of Munich) has just published an epidemiological study that confirms this finding. It shows that the lower susceptibility ...
Quantum simulator becomes accessible to the world
2011-02-24
Experimental physicists have put a lot of effort in isolating sensitive measurements from the disruptive influences of the environment. In an international first, Austrian quantum physicists have realized a toolbox of elementary building blocks for an open-system quantum simulator, where a controlled coupling to an environment is used in a beneficial way. This offers novel prospects for studying the behavior of highly complex quantum systems. The researchers have published their work in the scientific journal Nature.
Many phenomena in our world are based on the nature ...