Posts tagged balance
Articles and news from the latest research reports.
Wii Balance Board Induces Changes in the Brains of MS Patients
A balance board accessory for a popular video game console can help people with multiple sclerosis (MS) reduce their risk of accidental falls, according to new research published online in the journal Radiology. Magnetic resonance imaging (MRI) scans showed that use of the Nintendo Wii Balance Board system appears to induce favorable changes in brain connections associated with balance and movement.
Balance impairment is one of the most common and disabling symptoms of MS, a disease of the central nervous system in which the body’s immune system attacks the protective sheath around nerve fibers. Physical rehabilitation is often used to preserve balance, and one of the more promising new tools is the Wii Balance Board System, a battery-powered device about the size and shape of a bathroom scale. Users stand on the board and shift their weight as they follow the action on the television screen during games like slalom skiing.
While Wii balance board rehabilitation has been reported as effective in patients with MS, little is known about the underlying physiological basis for any improvements in balance.
Researchers recently used an MRI technique called diffusion tensor imaging (DTI) to study changes in the brains of 27 MS patients who underwent a 12-week intervention using Wii balance board-based visual feedback training. DTI is a non-conventional MRI technique that allows detailed analysis of the white matter tracts that transmit nervous signals through the brain and body.
MRI scans of the MS patients showed significant effects in nerve tracts that are important in balance and movement. The changes seen on MRI correlated with improvements in balance as measured by an assessment technique called posturography.
These brain changes in MS patients are likely a manifestation of neural plasticity, or the ability of the brain to adapt and form new connections throughout life, according to lead author Luca Prosperini, M.D., Ph.D., from Sapienza University in Rome, Italy.
"The most important finding in this study is that a task-oriented and repetitive training aimed at managing a specific symptom is highly effective and induces brain plasticity," he said. "More specifically, the improvements promoted by the Wii balance board can reduce the risk of accidental falls in patients with MS, thereby reducing the risk of fall-related comorbidities like trauma and fractures."
Dr. Prosperini noted that similar plasticity has been described in persons who play video games, but the exact mechanisms behind the phenomenon are still unknown. He hypothesized that changes can occur at the cellular level within the brain and may be related to myelination, the process of building the protective sheath around the nerves.
The rehabilitation-induced improvements did not persist after the patients discontinued the training protocol, Dr. Prosperini said, most likely because certain skills related to structural changes to the brain after an injury need to be maintained through training.
"This finding should have an important impact on the rehabilitation process of patients, suggesting that they need ongoing exercises to maintain good performance in daily living activities," Dr. Prosperini said.
Ballet dancers’ brains adapt to stop them feeling dizzy
Scientists have discovered differences in the brain structure of ballet dancers that may help them avoid feeling dizzy when they perform pirouettes.
The research suggests that years of training can enable dancers to suppress signals from the balance organs in the inner ear.
The findings, published in the journal Cerebral Cortex, could help to improve treatment for patients with chronic dizziness. Around one in four people experience this condition at some time in their lives.
Normally, the feeling of dizziness stems from the vestibular organs in the inner ear. These fluid-filled chambers sense rotation of the head through tiny hairs that sense the fluid moving. After turning around rapidly, the fluid continues to move, which can make you feel like you’re still spinning.
Ballet dancers can perform multiple pirouettes with little or no feeling of dizziness. The findings show that this feat isn’t just down to spotting, a technique dancers use that involves rapidly moving the head to fix their gaze on the same spot as much as possible.
Researchers at Imperial College London recruited 29 female ballet dancers and, as a comparison group, 20 female rowers whose age and fitness levels matched the dancers’.
The volunteers were spun around in a chair in a dark room. They were asked to turn a handle in time with how quickly they felt like they were still spinning after they had stopped. The researchers also measured eye reflexes triggered by input from the vestibular organs. Later, they examined the participants’ brain structure with MRI scans.
In dancers, both the eye reflexes and their perception of spinning lasted a shorter time than in the rowers.
Dr Barry Seemungal, from the Department of Medicine at Imperial, said: “Dizziness, which is the feeling that we are moving when in fact we are still, is a common problem. I see a lot of patients who have suffered from dizziness for a long time. Ballet dancers seem to be able to train themselves not to get dizzy, so we wondered whether we could use the same principles to help our patients.”
The brain scans revealed differences between the groups in two parts of the brain: an area in the cerebellum where sensory input from the vestibular organs is processed and in the cerebral cortex, which is responsible for the perception of dizziness.
The area in the cerebellum was smaller in dancers. Dr Seemungal thinks this is because dancers would be better off not using their vestibular systems, relying instead on highly co-ordinated pre-programmed movements.
“It’s not useful for a ballet dancer to feel dizzy or off balance. Their brains adapt over years of training to suppress that input. Consequently, the signal going to the brain areas responsible for perception of dizziness in the cerebral cortex is reduced, making dancers resistant to feeling dizzy.
“If we can target that same brain area or monitor it in patients with chronic dizziness, we can begin to understand how to treat them better.”
Another finding in the study may be important for how chronic dizzy patients are tested in the clinic. In the control group, the perception of spinning closely matched the eye reflexes triggered by vestibular signals, but in dancers, the two were uncoupled.
“This shows that the sensation of spinning is separate from the reflexes that make your eyes move back and forth,” Dr Seemungal said. “In many clinics, it’s common to only measure the reflexes, meaning that when these tests come back normal the patient is told that there is nothing wrong. But that’s only half the story. You need to look at tests that assess both reflex and sensation.”
Keeping your balance
It happens to all of us at least once each winter in Montreal. You’re walking on the sidewalk and before you know it you are slipping on a patch of ice hidden under a dusting of snow. Sometimes you fall. Surprisingly often you manage to recover your balance and walk away unscathed. McGill researchers now understand what’s going on in the brain when you manage to recover your balance in these situations. And it is not just a matter of good luck.
Prof. Kathleen Cullen and her PhD student Jess Brooks of the Dept of Physiology have been able to identify a distinct and surprisingly small cluster of cells deep within the brain that react within milliseconds to readjust our movements when something unexpected happens, whether it is slipping on ice or hitting a rock when skiing. What is astounding is that each individual neuron in this tiny region that is smaller than a pin’s head displays the ability to predict and selectively respond to unexpected motion.
This finding both overturns current theories about how we learn to maintain our balance as we move through the world, and also has significant implications for understanding the neural basis of motion sickness.
Scientists have theorized for some time that we fine-tune our movements and maintain our balance, thanks to a neural library of expected motions that we gain through “sensory conflicts” and errors. “Sensory conflicts” occur when there is a mismatch between what we think will happen as we move through the world and the sometimes contradictory information that our senses provide to us about our movements.
This kind of “sensory conflict” may occur when our bodies detect motion that our eyes cannot see (such as during plane, ocean or car travel), or when our eyes perceive motion that our bodies cannot detect (such as during an IMAX film, when the camera swoops at high speed over the edge of steep cliffs and deep into gorges and valleys while our bodies remain sitting still). These “sensory conflicts” are also responsible for the feelings of vertigo and nausea that are associated with motion sickness.
But while the areas of the brain involved in estimating spatial orientation have been identified for some time, until now, no one has been able to either show that distinct neurons signaling “sensory conflicts” existed, nor demonstrate exactly how they work. “We’ve known for some time that the cerebellum is the part of the brain that takes in sensory information and then causes us to move or react in appropriate ways,” says Prof. Cullen. “But what’s really exciting is that for the first time we show very clearly how the cerebellum selectively encodes unexpected motion, to then send our body messages that help us maintain our balance. That it is such a very exact neural calculation is exciting and unexpected.”
By demonstrating that these “sensory conflict” neurons both exist and function by making choices “on the fly” about which sensory information to respond to, Cullen and her team have made a significant advance in our understanding of how the brain works to keep our bodies in balance as we move about.
The research was done by recording brain activity in macaque monkeys who were engaged in performing specific tasks while at the same time being unexpectedly moved around by flight-simulator style equipment.
(Source: eurekalert.org)
New Genetic Disorder of Balance and Cognition Discovered
The family of disorders known as ataxia can impair speech, balance and coordination, and have varying levels of severity. Scientists from the Universities of Oxford and Edinburgh have identified a new member of this group of conditions which is connected to ‘Lincoln ataxia’, so called because it was first found in the relatives of US President Abraham Lincoln. The results are published in the journal PLOS Genetics.
Lincoln ataxia affects the cerebellum, a crucial part of the brain controlling movement and balance. It is caused by an alteration in the gene for ‘beta-III spectrin’, a protein found in the cerebellum. Each person has two copies of a gene, and in Lincoln ataxia there is an alteration in only one of the two copies. Unexpectedly, the British scientists have found cases of alterations in both copies of the gene, causing a novel disorder called ‘SPARCA1’ which is associated with a severe childhood ataxia and cognitive impairment.
This is the first report of any spectrin-related disorder where both copies of the gene are faulty and has given important insights into both Lincoln ataxia and SPARCA1.
The work was done using whole genome sequencing, a relatively new technology which allows all of a person’s genetics information to be analysed. In addition to sequencing work, the scientists characterized the condition using mice lacking beta-III spectrin. This analysis, combined with previous work, links the protein defect to changes in nerve-cell shape in the brain areas associated with cognition and coordinated movements. The work shows that loss of normal beta-III spectrin function underlies both SPARCA 1 and Lincoln ataxia, but a greater loss of beta-III spectrin is required before cognition problems arise.
Most creatures need a good sense of balance — especially tree-dwellers that swing among high branches. In mammals, the ability largely comes from three loop-shaped structures in the inner ear called semicircular canals; in most species, the size, shape, and arrangement of those loops (inset) is extremely consistent from one individual to another. But in three-toed sloths (such as Bradypus variegatus, the brown-throated three-toed sloth, pictured), many proportions of the semicircular canals are surprisingly variable from one sloth to another.
The overall variability is at least twice that seen in other species of mammals the team analyzed, researchers report online today in the Proceedings of the Royal Society B. That high degree of variation stems from the sloths’ languid lifestyle, the researchers suggest.
Sloths, which move extremely slowly when they move at all, don’t require the sense of balance that a swift, agile creature such as a primate needs. The finding supports one of Charles Darwin’s notions about evolution: If an organ isn’t crucial, variations in its structure or performance aren’t lost over time, keeping the potpourri in the population.
Decoding the secrets of balance
July 25, 2012
(Medical Xpress) — New understanding of how the brain processes information from inner ear offers hope for sufferers of vertigo.
If you have ever looked over the edge of a cliff and felt dizzy, you understand the challenges faced by people who suffer from symptoms of vestibular dysfunction such as vertigo and dizziness. There are over 70 million of them in North America. For people with vestibular loss, performing basic daily living activities that we take for granted (e.g. dressing, eating, getting in and out of bed, getting around inside as well as outside the home) becomes difficult since even small head movements are accompanied by dizziness and the risk of falling.
We’ve known for a while that a sensory system in the inner ear (the vestibular system) is responsible for helping us keep our balance by giving us a stable visual field as we move around. And while researchers have already developed a basic understanding of how the brain constructs our perceptions of ourselves in motion, until now no one has understood the crucial step by which the neurons in the brain select the information needed to keep us in balance.
The way that the brain takes in and decodes information sent by neurons in the inner ear is complex. The peripheral vestibular sensory neurons in the inner ear take in the time varying acceleration and velocity stimuli caused by our movement in the outside world (such as those experienced while riding in a car that moves from a stationary position to 50 km per hour). These neurons transmit detailed information about these stimuli to the brain (i.e. information that allows one to reconstruct how these stimuli vary over time) in the form of nerve impulses.
Scientists had previously believed that the brain decoded this information linearly and therefore actually attempted to reconstruct the time course of velocity and acceleration stimuli. But by combining electrophysiological and computational approaches, Kathleen Cullen and Maurice Chacron, two professors in McGill University’s Department of Physiology, have been able to show for the first time that the neurons in the vestibular nuclei in the brain instead decode incoming information nonlinearly as they respond preferentially to unexpected, sudden changes in stimuli.
It is known that representations of the outside world change at each stage in this sensory pathway. For example, in the visual system neurons located closer to the periphery of the sensory system (e.g. ganglion cells in the retina) tend to respond to a wide range of sensory stimuli (a “dense” code), whereas central neurons (e.g. in the primary visual cortex at the back of the head tend to respond much more selectively (a “sparse” code). Chacron and Cullen have discovered that the selective transmission of vestibular information they were able to document for the first time occurs as early as the first synapse in the brain. “We were able to show that the brain has developed this very sophisticated computational strategy to represent sudden changes in movement in order to generate quick accurate responses and maintain balance,” explained Prof. Cullen. “I keep describing it as elegant, because that’s really how it strikes me.”
This kind of selectivity in response is important for everyday life, since it enhances the brain’s perception of sudden changes in body posture. So that if you step off an unseen curb, within milliseconds, your brain has both received the essential information and performed the sophisticated computation needed to help you readjust your position. This discovery is expected to apply to other sensory systems and eventually to the development of better treatments for patients who suffer from vertigo, dizziness, and disorientation during their daily activities. It should also lead to treatments that will help alleviate the symptoms that accompany motion and/or space sickness produced in more challenging environments.
Provided by McGill University
Source: medicalxpress.com