UNews - tinnitus

Auditory research study to further tinnitus knowledge

caroline.zentner — Thu, 23 Jun 2016 15:29:26 +0000

In the quest to learn more about the brain and brain diseases, Dr. Majid Mohajerani has been assembling a team of researchers—three graduate students, three post-doctoral researchers, a research associate and two technicians—as he’s been building a state-of-the-art optical imaging lab.

Dr. Michael Kyweriga is one of the post-doctoral researchers and he’s investigating tinnitus. He’s currently conducting a study to determine if the parietal association area of the brain is involved in a task that requires a transgenic mouse to discriminate between two auditory tones.

Dr. Michael Kyweriga

“Many people are aware of the cocktail party effect, which is when you’re in a noisy environment and you’re talking to your friend but there’s all these distracting sounds. You are able to tune out those distracting sounds. That’s a form of attention called top-down control, where you try to suppress other inputs and pay attention to what your friend is saying. How the brain does this is not well understood,” he says.

Researchers like Kyweriga have some candidate regions of the brain that might be involved, one of them being the parietal association area. At a cocktail party, a person’s ears receive information about the sounds in the environment. The signals travel on the auditory nerves and on to the brain’s auditory cortex for further processing.

“When the signals get up into the cerebral cortex—the wrinkly, thinky part of the brain—that’s where we start assigning meaning to sounds, identifying songs or a person’s voice. Beyond that are these association areas that are now starting to draw in memories and accessing other parts of the brain that pull all this together,” says Kyweriga. “We’re trying to deal with the information as we try to listen to a friend speak and some people will close a door or put their dominant ear closer to the person to cut out other distractors.”

How people are able to direct their attention through top-down control, by willing themselves to pay attention, has eluded scientists for a long time. Some scientists have speculated that tinnitus could be a disorder of top-down control. If Kyweriga can show that the parietal association area is involved in top-down control, then he can test whether tinnitus is the result of faulty top-down control. Only with the tools in Mohajerani’s lab can these hypotheses be tested.

Kyweriga is training mice to learn whether a high- or low-frequency tone is associated with a reward. Once the mice have been sufficiently trained, a fibre optic connector is implanted close to the surface of their brains. To test his hypothesis, the mice do the auditory task again.

“While they’re doing the task and, simultaneously with them getting the sound, we’re going to turn on the blue light and that should either disrupt or enhance their neural responses to the sound,” says Kyweriga. “This is a really cool set of experiments that we’re able to do here with all the technology that we have and get to answering these long-standing questions we have in neuroscience about how our brains are able to do these type of things.”

As researchers like Kyweriga uncover more of the secrets of how the brain works, the higher is the likelihood of developing therapeutic approaches that will help people with tinnitus.

While Kyweriga uses lasers to alter the behaviour of his mice subjects, another post-doctoral researcher, Dr. Maurice Needham, uses lasers to view neuronal activity and provides expertise on the technical side of things. He’s in charge of making sure the optical equipment runs properly, including the two new shiny two-photon microscopes placed on a stainless steel table that’s suspended on air.

Dr. Maurice Needham

“The reason it’s suspended on air is to eliminate vibrations because when you have so many components working so finely, you have to ensure that any minor movements emanating from the building will be absorbed by this table. Any vibrations from the ground first have to move the heavy stainless steel table and even if that happens, the air cushion protects the stability of the tabletop and thus the images,” says Needham. “When it comes to two-photon imaging, this is probably the most advanced system you can buy.”

Needham has been at the U of L for five years and during that time he’s become more familiar with imaging systems. When the two-photon microscopes were installed, Needham watched, listened and learned so now he’s in charge of making sure they continue to work and performing any necessary repairs.

“Once Majid started increasing the amount of imaging systems here, we connected because I was interested,” he says.

While two-photon systems have been available for years, Mohajerani’s system is special. In addition to being very fast, it can simultaneously stimulate specific brain regions while viewing the subsequent response. It can also look much deeper into brain tissue than previous systems. This will be of great benefit to many experiments in Mohajerani’s lab, including Kyweriga’s work on tinnitus.

“All research requires the sharing of data. Seeing numbers and graphs is one thing but seeing pretty images is always the best. A picture is worth a thousand words,” says Needham. “We are one of only two labs in Canada with this imaging set-up, making us competitive on the world stage for neuroscience research. These systems, along with the new two-photon tomography system, will elevate this research centre’s technical abilities to compete with the best universities in the world.”

U of L researcher to investigate tinnitus through funding from Alberta Innovates Health Solutions

caroline.zentner — Mon, 09 Mar 2015 20:02:27 +0000

Dr. Michael Kyweriga, a postdoctoral fellow in Dr. Majid Mohajerani’s lab at the ��Ѹ��Դ��߿�Ƭ of Lethbridge, will be able to build understanding of tinnitus thanks to a postgraduate fellowship from Alberta Innovates Health Solutions.

Tinnitus, a condition in which a person hears constant ringing, buzzing or hissing noises, often occurs as a result of hearing loss or from prolonged exposure to loud noises such as gunfire, sirens or loud music. Approximately three per cent of the population has chronic tinnitus although that’s expected to increase as more people listen to loud music and videos on their personal devices. Kyweriga became interested in tinnitus during his time in the United States Navy.

“One of my jobs as a hospital corpsman was to give marines hearing tests,” he says. “I noticed a lot of them complained about ringing in their ears, or tinnitus, and hearing loss, especially those who were five or 10 years into their service.”

Kyweriga, who was born in Winnipeg into a military family, joined the U.S. Navy a couple of years after finishing high school. At the time, his father, a member of the Canadian Air Force, decided to retire in Montana. Green card in hand, Kyweriga enlisted for five years beginning in 1997. He trained to become a hospital corpsman, a job that entails providing emergency treatment for combat injuries. In the process of his training, he became fascinated by the brain-body connection.

“Even before I was honourably discharged from the Navy, I knew I wanted to go to college and be a neuroscientist some day,” he says.

Given the frequency with which military personnel were affected by tinnitus, Kyweriga thought it would be a fruitful topic of research. The American Tinnitus Association indicates tinnitus is the leading cause of disability of U.S. troops returning from Iraq and Afghanistan, with more than $1 billion paid out in claims in 2009. Tinnitus is also one of the top reasons for disability pension claims by current and former male RCMP members.

“Hearing loss and tinnitus, especially, are major health issues and the costs are expected to keep increasing,” he says.

People with tinnitus can have difficulty concentrating to the point it interferes with their job and other daily activities. Playing other sounds to mask the ringing seems to be the only way to get a measure of relief.

“There’s no cure or effective treatment right now. Antidepressants, white noise, reduce your stress — those are really the only things you can do for tinnitus,” he says. “We don’t understand fully how it works and that’s where I want to go with my research.”

In tinnitus, the brain perceives a sound where none has been created. The brain’s auditory cortex is laid out much like a keyboard. When a particular frequency is damaged, the neighbouring regions remap the cortex, which is likely why, when the two-kilohertz (kHz) region is damaged for example, the three-kHz region remaps over it and one hears a sound at three kHz. Researchers suspect remapping is why the ringing sounds are a half-octave above the damaged frequency but Kyweriga plans to test this hypothesis.

After completing his doctorate at the ��Ѹ��Դ��߿�Ƭ of Oregon, Kyweriga searched for a fellowship position. Impressed by scientists like Mohajerani, Drs. Bruce McNaughton and Bryan Kolb, the tools and techniques available at the U of L and the multicultural, collaborative working environment he’d be joining, Kyweriga came to the U of L last year. He was elated to learn he’d been granted an award from Alberta Innovates worth $50,000 over three years, along with a $5,000 stipend per year for equipment and travel to conferences.

Given researchers know exposure to loud noises causes changes in the auditory cortex of the brain, Kyweriga will be working with mice to see if the changes cause tinnitus and whether the changed areas can be manipulated to alleviate tinnitus.

“I really think this is going to lead to a better understanding of what’s going on in the mouse brain, and the results may translate to the general public,” he says, adding he hopes his research will ultimately lead to medical treatments and interventions that will alleviate tinnitus for people and especially those who go into harm’s way. “I really want to thank our men and women in uniform by helping to reduce their suffering.”

UNews - tinnitus

Auditory research study to further tinnitus knowledge

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U of L researcher to investigate tinnitus through funding from Alberta Innovates Health Solutions

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