Relief could soon be on the way for sufferers of tinnitus, the annoying and occasionally debilitating persistent ringing in some people's ears, according to a new study that found that stimulating a nerve in the neck might "reboot" the defective auditory neurons responsible for the buzz. Persistent tinnitus affects around 23 million American adults. Exposure to extremely loud noises is the most common cause, and frequent exposure over long periods of time can accumulate damage.

When audio-sensing cells of the ear become damaged, they send faulty signals to the brain that result in a constant high-pitched ringing.

"The pathology is actually in the brain, it's not in the ear," said the study's co-author, Navzer Engineer, an audiologist at the medical device company MicroTransponder, Inc.

Tinnitus is especially a problem for military veterans who've been repeatedly exposed to loud blasts and equipment noise, Engineer said. Auditory problems are among the most common service-related problems reported by veterans returning from Iraq.

So far, scientists searching for a cure to tinnitus have come up empty, but Engineer and co-author Michael Kilgard, an audiologist at the University of Texas, Dallas, wanted to try a technique that's been successful with motor control disorders: electrically stimulating a nerve to "reset" neurons to their default state and halt the faulty misfiring.

The researchers exposed rats in an experiment to loud noises at specific frequencies to induce tinnitus. They trained the rats to startle whenever there was a pause in the continuously played frequency. They determined the rats with tinnitus by seeing which ones didn't startle -- these rats never noticed the pause because their brains filled in the silence with tinnitus's ringing.

In these tinnitus-afflicted rats, Engineer and Kilgard hooked up electrodes to the vagus nerves, which run close to the carotid artery in the neck and releases brain chemicals such as acetylcholine and norepinephrine. These chemicals have been linked in previous studies with making neurons more plastic and susceptible to change.

Over the course of 20 days, the researchers delivered intermittent electrical impulses accompanied by a high-pitched tone matching the frequency of their tinnitus.

"This tells the neuron that this is an important sensation, so pay attention to this," Engineer said.

After the nerve stimulation therapy, the researchers repeated the tinnitus test and found that the rats jumped when they heard the pause, which suggests their tinnitus had been cured, Engineer said. Rats with tinnitus who didn't receive the vagus nerve stimulations, or who received them without the accompanying tones, didn't show any improvement. The researchers published their results this week in the journal Nature.

Engineer and Kilgard are already preparing for clinical trials in humans and expect to have results by the end of this year. Because vagus nerve stimulation is minimally invasive and is already FDA-approved to treat other disorders such as epilepsy and depression, Engineer said he's hopeful it will soon be able to help humans suffering from tinnitus.

Richard Tyler, an audiologist at the University of Iowa, said it's difficult to know whether the rats tested actually had tinnitus, so proof will have to wait until the therapy is tested on humans. But he believes the researchers on the right track. "I think it's still pretty early-stage," she said, "but at the present, there's no cure for tinnitus, so this looks promising."