Stimulating the vagus nerve may help block phantom sounds by reorganizing the brain

MIT Technology Review, May 27, 2010, by Emily Singer  –  Electrically stimulating the vagus nerve, which connects the brain and the visceral organs, could help temper the phantom sounds that plague tinnitus sufferers. Researchers from Microtransponder, a Dallas-based startup developing wireless stimulation technology, reported at a neurotechnology conference in Boston this week that the approach works in animals with auditory damage that mimics the disorder. The company is adapting its neurostimulation technology, currently being developed for chronic pain, to target the vagus nerve.

Tinnitus, the false perception of ringing or other sounds in the ear, affects millions of people worldwide. Most often associated with hearing loss, it has become an especially common problem in soldiers exposed to loud blasts. The severity of the disorder varies widely, from relatively benign to debilitating, and the few existing treatments tend to mask the intrusive sound rather than eliminate it.

While it’s unclear exactly what causes tinnitus, research suggests it arises from the brain’s attempt to compensate for hearing loss. Damage to the inner ear, which translates sound vibrations into neural signals for the brain, results in less input to the brain’s auditory pathways. The brain appears to try to make up for this loss of input by increasing activity, which may in turn result in phantom sounds.

Michael Kilgard, a neuroscientist at the University of Texas, aims to reverse this maladaptive reorganization using a combination of electrical stimulation and sound. Kilgard has previously shown that stimulating part of the brain called the nucleus basalis while playing a particular tone triggers the auditory cortex to reorganize to become hyper-responsive to that tone. To treat tinnitus, the idea is to stimulate this area while playing all sound frequencies except the one corresponding to a patient’s phantom sound, thus signaling to the brain to become more responsive to all these other frequencies. If successful, this would rebalance the auditory cortex.

Rather than targeting the brain directly in humans, Kilgard turned to the vagus nerve, part of the nervous system that connects the stomach, liver, and other organs to the brain. Implanted devices that stimulate the vagus nerve are currently approved to treat depression and epilepsy and are being tested for other disorders.

Researchers plan to test the concept in people with tinnitus in upcoming clinical trials in Belgium. Kilgard says the researchers will use simple electrodes, which are implanted at the neck and stimulated with an external device. While the exact parameters are still to be determined, patients will undergo treatment for half an hour to an hour each day, for days or weeks. Unlike vagus nerve stimulation for epilepsy, which involves chronic stimulation, treatment for tinnitus will likely be for a limited period of time, researchers say.

In conjunction with these clinical tests, Microtransponder is modifying its existing technology for tinnitus. Unlike other stimulation devices, Microtransponder’s system is wireless and has no batteries. The implanted portion consists of small electrodes and a small coil. An external battery-powered coil worn like a cuff on the arm or leg powers the device. “The idea would be to inject the wireless device and then put a coil around the neck to activate it [during a treatment session],” says Kilgard. “If the tinnitus comes back five years later, the device is still there and you can do the treatment again.

Harvard’s Melcher says the approach is very interesting, though “whether it works is an open question.” She points out that “we are still trying to sort out what aspects of brain plasticity are involved in tinnitus. There may be different kinds of tinnitus, with different types of brain activity giving rise to the perception of sounds that aren’t there.” All of these may require different treatments.

Tinnitus is the name given to the condition of noises ‘in the ears’ and/or ‘in the head’ with no external source. Tinnitus noises are described variously as ringing, whistling, buzzing and humming.

The noise/s may be heard in one ear, both ears or in the middle of the head or it may be difficult to pinpoint its exact location. The noise may be low, medium or high-pitched. There may be a single noise or two or more components. The noise may be continuous or it may come and go.

What causes tinnitus?

Tinnitus is not a disease or an illness, it is a symptom generated within a person’s own auditory pathways. Although it is often assumed that tinnitus occurs as a result of disease of the ears, this is often not the cause. The precise cause of tinnitus is still not fully understood but is usually associated with some hearing deficits. Damage caused to the hearing nerve in the inner ear is one of the most commons causes of tinnitus. Listening to loud noises such as music from an ipod, heavy machinery, and firearms can also cause tinnitus. There is no way to cure tinnitus and age can be another factor that plays a role in the onset of tinnitus symptoms.

Who gets tinnitus?

Experiences of tinnitus are very common in all age groups, especially following exposure to loud noise, however, it is unusual for it to be a major problem. There is a widely held misconception that tinnitus is confined to the elderly, but various studies have shown that it can occur at any age, even quite young children. Mild tinnitus is common – about 10 per cent of the population have it all the time and, in up to one per cent of adults, this may affect the quality of their life.

Who’s at Risk?

 

Many professions and activites can put you at risk for getting tinnitus. People around loud industial noise, such machinists, airport workers, military personnel & carpenters are all at risk. Activities such as listening to loud music, whether on an mp3 player, at a concert, or in a nightclub can also put you in the at-risk category.

GoogleNews.com  —  Acupuncture and trigger point therapy may be effective treatments for people suffering from tinnitus — a ringing in the ears — a U.S. study found.

Susan Shore of the University of Michigan’s Kresge Hearing Research Institute said nerves that “sense touch” in the face and neck may be behind the ringing that people with tinnitus hear.

The study, published online in the European Journal of Neuroscience, said touch-sensing nerve cells step up their activity in the brain after hearing cells are damaged, and hyperactivity of these touch-sensing neurons likely plays an important role in tinnitus.

The research findings were made in studies involving animals, but the research suggests treatments such as acupuncture — if used to target nerves in the head and neck — may provide relief for some people plagued by tinnitus.

University of Alabama professor Craig Formby looks on as Adam Jones spins in a Roto-Tilt Chair in a demonstration in the AIME Building on the University of Alabama campus.

GoogleNews.com, by Adam Jones  –  A University of Alabama researcher is leading a $3.2 million clinical study of a treatment of severe tinnitus, or ringing in the ear.

Tinnitus?

What it is: Ringing in the ears. About 50 million Americans say they have experienced it, but fewer than 5 million say it is debilitating.
What causes it: Causes aren’t fully known, but in some cases loud noises, such as gunfire, can trigger it.
How to treat it: There is no known cure, since tinnitus isn’t fully understood. Formby’s trial will combine counseling with a hearing aid-like device that makes a sound in the patient’s ear that will blend in with the ringing. With prolonged use, patients may begin to become less affected by tinnitus.

“There’s been a lot of attempts to come up with treatments, but nothing has been very successful,” said Craig Formby, a UA graduate research professor in audiology.

About 50 million Americans say they suffer from tinnitus, but a smaller group, less than 5 million, say the ringing is debilitating. For those people, tinnitus is an all-consuming disease that dominates their life, Formby said.

“We’re trying to bring people back into the pack of those who aren’t bothered by it,” he said.

The treatment being tested is non-medical and is hoped to help patients live with the disease. There is no known cure for the ringing, since the disease is not fully understood.

The new method, called tinnitus retraining therapy, will combine current methods of counseling with a hearing aid like device that will pipe a sound into the ear that blends with the ringing, Formby said.

Patients are encouraged to use the device all day in an effort to help them cope with the ringing. They are asked to try to live a normal day and forget the devices are in, he said.

Previous work has shown about 80 percent of people who undergo the treatment and use the device consistently report diminished influence of tinnitus, Formby said.

Formby didn’t invent the treatment, but he and his UA team will lead the trial, paid for by a $3.2 million award from the National Institute of Deafness and Other Communication Disorders. If successful, the treatment will likely be accepted as standard.

“It’s not new or innovative, it just needs to be tested out,” Formby said. “Ours is sort of be-all, end-all of whether this works and is a viable treatment for people to consider.”

Researchers at Johns Hopkins University have a $2.4 million award to manage and analyze the study data. The project will be spread over five years, including four years for recruiting study participants and conducting the treatment and follow-up measurements, according to a UA news release.

All the patients will be drawn from U.S. Navy and Air Force hospitals in California, Texas, Maryland and Virginia. Researchers expect to recruit 228 participants for the study.

Tinnitus is the military’s Number 1 disability among veterans returning from the Middle East conflicts. In 2008, compensation for tinnitus disability in the Veteran Affairs medical system was more than $500 million and is projected to exceed $1.1 billion and affect more that 800,000 veterans by 2011, according to a UA news release.

It’s not clear what causes tinnitus, but loud noises, such as gunfire, can trigger it in some cases, Formby said.

For more info, Reach Adam Jones at 205-722-0230

They Fly 7,000+ Miles, 40 MPH, Nonstop in 9 Days –

Awesome Lesson in Tenacity and Focus

The Amazing Bar-tailed Godwit

The New York Times, May 27, 2010, by Carl Zimmer  –  In 1976, the biologist Robert E. Gill Jr. came to the southern coast of Alaska to survey the birds preparing for their migrations for the winter. One species in particular, wading birds called bar-tailed godwits, puzzled him deeply. They were too fat.

“They looked like flying softballs,” said Mr. Gill.

At the time, scientists knew that bar-tailed godwits spend their winters in places like New Zealand and Australia. To get there, most researchers assumed, the birds took a series of flights down through Asia, stopping along the way to rest and eat. After all, they were land birds, not sea birds that could dive for food in the ocean. But in Alaska, Mr. Gill observed, the bar-tailed godwits were feasting on clams and worms as if they were not going to be able to eat for a very long time.

“I wondered, why is that bird putting on that much fat?” he said.

Mr. Gill wondered if the bar-tailed godwit actually stayed in the air for a much longer time than scientists believed. It was a difficult idea to test, because he could not actually follow the birds in flight. For 30 years he managed as best he could, building a network of bird-watchers who looked for migrating godwits over the Pacific Ocean. Finally, in 2006, technology caught up with Mr. Gill’s ideas. He and his colleagues were able to implant satellite transmitters in bar-tailed godwits and track their flight.

The transmitters sent their location to Mr. Gill’s computer, and he sometimes stayed up until 2 in the morning to see the latest signal appear on the Google Earth program running on his laptop. Just as he had suspected, the bar-tailed godwits headed out over the open ocean and flew south through the Pacific. They did not stop at islands along the way. Instead, they traveled up to 7,100 miles in nine days — the longest nonstop flight ever recorded. “I was speechless,” Mr. Gill said.

Since then, scientists have tracked a number of other migrating birds, and they are beginning now to publish their results. Those results make clear that the bar-tailed godwit is not alone. Other species of birds can fly several thousand miles nonstop on their migrations, and scientists anticipate that as they gather more data in the years to come, more birds will join these elite ranks.

“I think it’s going to be a number of examples,” said Anders Hedenström of Lund University in Sweden.

As more birds prove to be ultramarathoners, biologists are turning their attention to how they manage such spectacular feats of endurance. Consider what might be the ultimate test of human endurance in sports, the Tour de France: Every day, bicyclists pedal up and down mountains for hours. In the process, they raise their metabolism to about five times their resting rate.

The bar-tailed godwit, by contrast, elevates its metabolic rate between 8 and 10 times. And instead of ending each day with a big dinner and a good night’s rest, the birds fly through the night, slowly starving themselves as they travel 40 miles an hour.

“I’m in awe of the fact that birds like godwits can fly like this,” said Theunis Piersma, a biologist at the University of Groningen.

Not long ago, ornithologists had far lower expectations for birds. Ruby-throated hummingbirds, for example, were known to spend winters in Central America and head to the United States for the summer. But ornithologists believed that the hummingbirds burned so much fuel flapping their wings that they simply could not survive a nonstop trip across the Gulf of Mexico. They were thought to have flown over Mexico, making stops to refuel.

In fact, ruby-throated hummingbirds returning north in the spring will set out from the Yucatán Peninsula in the evening and arrive in the southern United States the next afternoon.

In the 1960s, zoologists began to track bears and other mammals with radio collars, and then later moved on to satellite transmitters. All the while, ornithologists could only look on in envy. The weight and drag of the trackers made them impossible to put on migrating birds.

Over the past decade, however, transmitters have finally shrunk to a size birds can handle. In Mr. Gill’s first successful experiment with bar-tailed godwits, he and his colleagues slipped a battery-powered model weighing just under an ounce into the abdominal cavity of the birds, which weigh about 12 ounces and have a wingspan of 30 inches.

The epic odyssey that those transmitters recorded spurred Mr. Gill and other researchers to gather more data, both on bar-tailed godwits and other species. And even as they planned their experiments, tracking technology got better. This summer, for example, Mr. Gill will implant bar-tailed godwits with transmitters that weigh only six-tenths of an ounce.

Still, most migrating birds are so small that even a transmitter of that weight — about the same as three nickels — would be an intolerable burden. Fortunately, researchers have been able to scale down a different kind of tracking device. Known as a geolocator, it can get as light as two grains of rice, less than two-hundreths of an ounce. “Now we can track really small birds,” Dr. Hedenström said.

Geolocators can get so small because they do not communicate with satellites. Instead, they just record changing light levels. If scientists can recapture birds carrying geolocators, they can retrieve the data from the devices and use sophisticated computer programs to figure out the location of the birds based on the rising and setting of the sun.

In 2007, Carsten Egevang of Aarhus University in Denmark and his colleagues attached geolocators to Arctic terns nesting in Greenland. Based on years of bird spotting, the scientists knew that the terns migrated to the Southern Ocean around Antarctica and then returned to the Arctic the following spring. But they did not know much more than that. “It was all based on snapshots,” Dr. Egevang said.

In 2008, the scientists managed to capture 10 Arctic terns that had come back to Greenland. It then took them months to make sense of the data. “You have to use three kinds of special software,” Dr. Egevang said. “It takes quite a long time.”

The researchers reported this February that the Arctic terns flew from Greenland to a region of the Atlantic off the coast of North Africa, where they spent about three weeks. Unlike bar-tailed godwits, which wade on beaches for food, Arctic terns are ocean birds that can dive for fish in the open sea.

The Arctic terns then resumed their journey south. They spent five months in the Southern Ocean. “They probably just stayed on an iceberg and fished,” Dr. Egevang said.

In the spring, the terns then returned to the Arctic, often hugging the coasts of South America or Africa along the way. All told, the birds logged as much as 49,700 miles on their geolocators, the longest migration ever recorded. Over the 30-year lifetime of a tern, it may migrate about 1.5 million miles — the distance a spaceship would cover if it went to the moon and back three times.

Other scientists are now placing geolocators on small wading birds as well. In a paper to be published in the Wader Study Group Bulletin, a team of ornithologists describe attaching geolocators to four ruddy turnstones. The birds left northern Australia in May 2009 and flew nonstop to Taiwan, a distance of 4,700 miles.

After a few days in Taiwan, the ruddy turnstones took flight again, making a series of trips northward until they reached Alaska. At the end of the summer, three of the four birds took the same route back south. The fourth struck out on a different path. It flew 3,800 miles nonstop to the Gilbert Islands in the Pacific. From there, it flew 3,100 miles back to Australia.

Mr. Gill and his colleagues have recorded similar odysseys from other wading birds, using satellite transmitters. They found that bristle-thighed curlews fly as far as 6,000 miles without a stop, traveling from Alaska to the Marshall Islands. They have also recorded whimbrels flying 5,000 miles nonstop from Alaska to Central America.

This spring, scientists are attaching geolocators to more birds, and they expect to find new champions. One population of red knots, for example, is now arriving in Delaware Bay from its wintering grounds 5,500 miles away in Argentina. “My bet is that a lot of them make it in one go,” Dr. Piersma said.

The long journeys these transmitters are revealing pose a biological puzzle. Dr. Piersma and other scientists are trying to figure out how the birds manage to push their bodies so far beyond most animals, and why.

As Mr. Gill observed when he first observed bar-tailed godwits, a long journey requires a lot of food. It turns out that long-distance migrators will enlarge their liver and intestines as they feed, so that they can convert their food as fast as possible. They build up large breast muscles and convert the rest of their food to fat.

By the time the birds are ready to leave, their bodies are 55 percent fat. In humans, anything more than 30 percent is considered obese. But as soon as the birds are done eating, their livers and intestines become dead weight. They then essentially “eat” their organs, which shrink 25 percent. The birds use the proteins to build up their muscles even more.

Once they take flight, the birds take whatever help they can get. Bar-tailed godwits time their departure with the onset of stormy weather, so that they can take advantage of tailwinds. “That gives them an extra push,” Dr. Hedenström said.

The birds then fly for thousands of miles. How they get to their final destinations remains a mystery. One thing is clear: they somehow know where they are, even when they are flying over vast expanses of featureless ocean. “It’s as if they have a GPS on board,” Dr. Piersma said.

A bird like a bar-tailed godwit cannot rely on the tricks used by birds that take short migrations. They cannot follow landmarks, for example. Some birds use the Earth’s magnetic field to navigate. But they do so by sensing the tilt of the field lines. At the equator, the lines run parallel to the surface, making them useless for birds that have to travel between hemispheres. Dr. Piersma suspects that when birds travel several thousand miles, they have to combine several different navigation tricks together.

As spectacular as these migrations may be, it may not take long for birds to evolve them. Long-distance migrators are closely related to short-distance birds. It is possible that many birds have the potential to push themselves to make these vast journeys, but they do not because the costs outweigh the benefits.

When animals raise their metabolism above four or five times their resting rate (the Tour de France level), they can become so exhausted that they become very vulnerable to predators. They can even become more prone to getting sick. Birds that go on long migrations may have escaped this tradeoff.

Birds like the bar-tailed godwit have found places like the coast of Alaska where the supply of food is high and predators are scarce. By flying over the open ocean, they continue to avoid predators. They may also reduce their odds of picking up a parasite from another bird.

Their destinations are also safe enough for them to recover. Bar-tailed godwits that arrive in New Zealand face no predators, and so they can simply rest. “They just look exhausted. They’ll land and just go to sleep for several hours before they do anything else,” Mr. Gill said.

Unfortunately, some of the habitats on which these endurance champions depend are under serious threat. In the Delaware Bay, for example, fisherman are scooping up horseshoe crab eggs, which birds like the red knot travel thousands of miles to eat. When bar-tailed godwits return to Alaska in the spring, they make one stop along the coast of China and Korea, a favorite spot for many other migrating birds. The coastal wetlands there are disappearing fast, and many migrant birds are in decline.

“I hope we have these birds to study 100 years from now,” Dr. Piersma said. “But sometimes I wonder.”

Robert E. Gill Jr.
TRACKERS On Alaska’s Yukon River delta, scientists implant a transmitter in a bristle-thighed curlew. The birds fly as far as 6,000 miles without a stop.

Carsten Egevang

FOR THE RECORD Researchers attached geolocators weighing as little as two grains of rice to Arctic terns like this one.

Photo Credit: cjnew