Ringing in the ears may be a common, temporary symptom for some people, but when it is permanent and intense it is known as tinnitus and can be debilitating for a number of sufferers.
UB researchers have studied tinnitus for more than a decade at the Center for Hearing and Deafness in the Department of Communication Disorders and Sciences.
According to the principle investigator Richard Salvi, Ph.D., tinnitus is a phantom auditory sensation. People who have tinnitus typically experience ringing, buzzing or cricket-like sounds, but the phantom sound is not present in their environment.
Salvi compares tinnitus to Phantom Pains, a pain or feeling felt by a person in a part of the body that is no longer there, like after an amputation. He believes the two conditions are closely related.
"Tinnitus is basically a phantom sound. There is no real sound in the environment," Salvi said.
Wei Sun, Ph.D., a researcher at the Center for Hearing and Deafness, explains that studying tinnitus is difficult because of the condition's subjunctive nature.
"One thing that makes a study on tinnitus hard is that it is a perception...there is no objective measurement for tinnitus," Sun said.
The researchers explained that people only began to accept in the last one or two decades that tinnitus is not a condition with a psychological root, rather it is caused by a biological change in the brain.
According to Ed Lobarinas, Ph.D., a researcher at the Center for Hearing and Deafness, this finding is a milestone in their field.
"When you get away from the idea that people are imagining tinnitus versus there is some locus in the brain generating some activity that the person perceives as a real sound - that is a big difference," Lobarinas said.
The research is aimed toward uncovering the physiological and biological mechanisms that cause tinnitus.
"The first step was to develop these animal models. The second step, once you have an index of whether the tinnitus is there or not, then you move on to trying to look at the physiology and biological of tinnitus," Lobarinas said. "You can't look at the physiology if you don't have an index of whether a subject is experiencing tinnitus or not."
The researchers have already developed indices of measurement for the occurrence of tinnitus in animal models. The animal models are made to develop tinnitus through pharmaceutical means or noise trauma, according to the researchers.
The two methods of measuring the presence of tinnitus in the animal models were developed separately by Lobarinas and Sun. Both models require rats to distinguish between quiet and noise.
The animal model developed by Lobarinas uses rats trained to lick for water when it is quiet and not to lick for water whenever a sound is present.
According to Lobarinas, the rats without tinnitus will have a high lick rate when it is quiet. Animals with the induced tinnitus will have a lower lick rate because the tinnitus condition will cause the rats to hear noise even when it is completely quiet.
"This is how we determine they no longer can hear quiet," Lobarinas said.
Another method called the Startle Reflex, developed by Sun, measures whether or not the animal perceives a phantom sound.
This method involves playing a background noise for the animal models. A silent period acts as a warning for a subsequent larger sound - the startle stimulus. The silent period is set into the background noise. An animal model with induced tinnitus will not be able to distinguish the quiet from the background noise because the tinnitus will mask the quiet. A normal rat will be able to detect the silence before the startle stimulus and as a result will be less startled.
The two methods that measure the tinnitus in animal models enable the researchers to look at the brains of the animal models through neurophysiology. By determining which animal models have tinnitus researchers can move on to look at brain imaging and positron emission tomography (PET) scanning.
Salvi cites the two goals for the next five years, in which the grant is applicable: to identify the neurophysiological changes when tinnitus is present and to test drugs that suppress the behavioral evidence of tinnitus.
"We want to induce it and we want to find out how to suppress it," Salvi said.
Lobarinas says this dual approach is a novel way of working for them.
Researchers ultimately want to understand the underlying pathology of the condition to help relieve the problem in the future.
Photo: Courtesy of Laron Fomby
