Nav: Home

Magic helps unmask how the brain works

August 01, 2017

Tricks and illusions, once the domain of magicians, are helping scientists unveil how the brain works.

Here's one you can try using a tabletop mirror. Place your left hand on the table in front of the mirror's reflective surface and your right hand behind the mirror, about six inches away, where you can't see it. Now tap the table surface with both hands while looking at your reflection. Within a minute, you'll feel as though the hand you see reflected in the mirror is your right hand and it's right next to the mirror -- even though the hidden hand did not move.

This classic "mirror box" illusion has been used in a number of neuroscience studies, including with amputees as a possible therapy to alleviate phantom limb pain, where it may help the brain re-map and adapt to a missing limb.

Now, a new version of the mirror box illusion, developed by University of Delaware brain scientist Jared Medina and doctoral student Yuqi Liu, is pulling back more of the curtain on how the brain processes multiple sensory inputs to perceive our bodies and the world around us. Their study, which is supported by the National Science Foundation, appears in Scientific Reports, a multidisciplinary, open access journal from the publishers of Nature.

In their novel illusion, study participants placed their hands in opposite postures (one hand palm-up, the other palm-down), creating a conflict between visual and proprioceptive feedback for the hand behind the mirror. Proprioception is your so-called "sixth sense," the sense of where your body is in space, that comes from your muscles and joints. It's the sense that allows you to touch your nose with confidence even with your eyes closed.

After synchronous opening and closing of the two hands, the study participants felt that the hand behind the mirror rotated or completely flipped to match the hand reflection.

"All of a sudden during our experiments, you'd hear a little laugh of surprise when people experienced this neat sensation of feeling like their hand flipped, even though it did not move," Medina said.

Resolving battle of the senses

The illusion's effectiveness was influenced by the perceived difficulty of moving the hidden hand to the position viewed in the mirror. Less illusion occurred for more difficult rotations requiring more strain. Such biomechanical data, Medina said, is coded in the body schema, a representation of your body position in space that takes into account feedback from all the relevant senses, plus stored information from muscles and joints about what your body can and can't do.

According to Medina, the brain does "optimal integration" of incoming sensory information and then sorts out what the most reliable sense is.

"Vision is really precise," Medina said, "but proprioception -- the sense of where your body is in space--is noisier. So if there is a conflict between these senses, and vision is telling you that your hand is right there, but proprioception says it isn't, your brain is optimally calculating. Vision, because it is more precise, typically rules. However, in our study, the brain also appears to be considering additional information--biomechanical constraints from the body schema--in resolving this conflict between the senses."

Medina and his students are now using functional magnetic resonance imaging (fMRI) in UD's Center for Biomedical and Brain Imaging to further uncover how the brain calculates and integrates the vast inputs it receives from all the senses. This sophisticated tool can illuminate which regions of the brain are at work when performing a task. A better understanding of such brain processing could help advance new treatments for patients with brain injuries such as strokes, chronic pain and other disorders, and for developing artificial limbs that feel like a part of the body.

"How do you embody an artificial limb? It has to respect the laws of the body you've learned all your life," Medina noted. "It's quite important to figure out how the brain solves the problem of multisensory information, and how that relates to embodiment and our sense of self. These cool tricks and illusions are a path to understanding how the mind works."
-end-


University of Delaware

Related Brain Articles:

Study describes changes to structural brain networks after radiotherapy for brain tumors
Researchers compared the thickness of brain cortex in patients with brain tumors before and after radiation therapy was applied and found significant dose-dependent changes in the structural properties of cortical neural networks, at both the local and global level.
Blue Brain team discovers a multi-dimensional universe in brain networks
Using a sophisticated type of mathematics in a way that it has never been used before in neuroscience, a team from the Blue Brain Project has uncovered a universe of multi-dimensional geometrical structures and spaces within the networks of the brain.
New brain mapping tool produces higher resolution data during brain surgery
Researchers have developed a new device to map the brain during surgery and distinguish between healthy and diseased tissues.
Newborn baby brain scans will help scientists track brain development
Scientists have today published ground-breaking scans of newborn babies' brains which researchers from all over the world can download and use to study how the human brain develops.
New test may quickly identify mild traumatic brain injury with underlying brain damage
A new test using peripheral vision reaction time could lead to earlier diagnosis and more effective treatment of mild traumatic brain injury, often referred to as a concussion.
This is your brain on God: Spiritual experiences activate brain reward circuits
Religious and spiritual experiences activate the brain reward circuits in much the same way as love, sex, gambling, drugs and music, report researchers at the University of Utah School of Medicine.
Brain scientists at TU Dresden examine brain networks during short-term task learning
'Practice makes perfect' is a common saying. We all have experienced that the initially effortful implementation of novel tasks is becoming rapidly easier and more fluent after only a few repetitions.
Balancing time & space in the brain: New model holds promise for predicting brain dynamics
A team of scientists has extended the balanced network model to provide deep and testable predictions linking brain circuits to brain activity.
New view of brain development: Striking differences between adult and newborn mouse brain
Spikes in neuronal activity in young mice do not spur corresponding boosts in blood flow -- a discovery that stands in stark contrast to the adult mouse brain.
Map of teenage brain provides evidence of link between antisocial behavior and brain development
The brains of teenagers with serious antisocial behavior problems differ significantly in structure to those of their peers, providing the clearest evidence to date that their behavior stems from changes in brain development in early life, according to new research led by the University of Cambridge and the University of Southampton, in collaboration with the University of Rome Tor Vergata in Italy.

Related Brain Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Anthropomorphic
Do animals grieve? Do they have language or consciousness? For a long time, scientists resisted the urge to look for human qualities in animals. This hour, TED speakers explore how that is changing. Guests include biological anthropologist Barbara King, dolphin researcher Denise Herzing, primatologist Frans de Waal, and ecologist Carl Safina.
Now Playing: Science for the People

#SB2 2019 Science Birthday Minisode: Mary Golda Ross
Our second annual Science Birthday is here, and this year we celebrate the wonderful Mary Golda Ross, born 9 August 1908. She died in 2008 at age 99, but left a lasting mark on the science of rocketry and space exploration as an early woman in engineering, and one of the first Native Americans in engineering. Join Rachelle and Bethany for this very special birthday minisode celebrating Mary and her achievements. Thanks to our Patreons who make this show possible! Read more about Mary G. Ross: Interview with Mary Ross on Lash Publications International, by Laurel Sheppard Meet Mary Golda...