Posted on 09/12/2011 2:28:34 PM PDT by Red Badger
Neuroscientists at the University of California, Berkeley, are offering hope to the 10 percent of the population who suffer from tinnitus – a constant, often high-pitched ringing or buzzing in the ears that can be annoying and even maddening, and has no cure.
Their new findings, published online last week in the journal Proceedings of the National Academy of Sciences, suggest several new approaches to treatment, including retraining the brain, and new avenues for developing drugs to suppress the ringing.
"This work is the most clearheaded documentation to this point of what's actually happening in the brain's cortex in ways that account for the ongoing genesis of sound," said Michael Merzenich, professor emeritus of otolaryngology at UC San Francisco and inventor of the cochlear implant, who was not involved with the research. "As soon as I read the paper, I said, 'Of course!' It was immediately obvious that this is almost certainly the true way to think about it."
Merzenich is also chief scientific officer at Posit Science, which develops software to retrain the brain, primarily to improve learning and memory but more recently to address problems like schizophrenia, Alzheimer's Disease and tinnitus.
"Two million Americans are debilitated by tinnitus; they can't work, they can't sleep. Its life destroying and a substantial cause of suicide," he said. "These experiments have led us to rethink how we attack the tinnitus by our training strategies."
Loud noises kill hair cells
According to coauthor Shaowen Bao, adjunct assistant professor in the Helen Wills Neuroscience Institute at UC Berkeley, tinnitus – pronounced TIN-it-tus or tin-NIGHT-us – is most commonly caused by hearing loss. Sustained loud noises, as from machinery or music, as well as some drugs can damage the hair cells in the inner ear that detect sounds. Because each hair cell is tuned to a different frequency, damaged or lost cells leave a gap in hearing, typically a specific frequency and anything higher in pitch.
Experiments in the past few years have shown that the ringing doesn't originate in the inner ear, though, but rather in regions of the brain – including the auditory cortex – that receives input from the ear.
Bao's experiments in rats with induced hearing loss explain why the neurons in the auditory cortex generate these phantom perceptions. They showed that neurons that have lost sensory input from the ear become more excitable and fire spontaneously, primarily because these nerves have "homeostatic" mechanisms to keep their overall firing rate constant no matter what.
"With the loss of hearing, you have phantom sounds," said Bao, who himself has tinnitus. In this respect, tinnitus resembles phantom limb pain experienced by many amputees,
One treatment strategy, then, is to retrain patients so that these brain cells get new input, which should reduce spontaneous firing. This can be done by enhancing the response to frequencies near the lost frequencies. Experiments over the past 30 years, including important research by Merzenich, have shown that the brain is plastic enough to reorganize in this way when it loses sensory input. When a finger is amputated, for example, the region of the brain receiving input from that finger may start handling input from neighboring fingers.
Bao noted that retraining the ear has been tried before, but with limited success. Most such attempts have taken patients with some residual hearing and trained their ears to be more sensitive to the affected frequencies. This wouldn't work for patients with profound hearing loss, however.
Most retraining is also based on the assumption that reorganization of the brain – that is, changing how frequencies "map" to regions of the auditory cortex – is a cause of the tinnitus. This is the opposite of Bao's conclusion.
"We argue that reorganizing the cortical map should be the goal, so that the nerves get some input and stop their tinnitus activity," he said. "You don't want to leave these cells without sensory input."
"We changed our (brain training) strategy from one where we completely avoided the tinnitus domain to one where we directly engage it and try to redifferentiate or reactivate it, and we seem to be seeing improvement," Merzenich said.
Drugs can boost inhibitors
Another treatment strategy, Bao said, is to find or develop drugs that inhibit the spontaneous firing of the idle neurons in the auditory cortex. Hearing loss causes changes at junctions between nerve cells, the so-called synapses, that both excite and inhibit firing. His experiments showed that tinnitus is correlated with lower levels of the inhibitory neurotransmitter GABA (gamma-aminobutyric acid), but not with changes in the excitatory neurotransmitters.
He demonstrated that two drugs that increase the level of GABA eliminated tinnitus in rats. Unfortunately, these drugs have serious side effects and cannot be used in humans. He has applied for several grants to start screening drugs for their ability to enhance GABA receptor function, increase the synthesis of GABA, slow the re-uptake of GABA around nerve cells, or slow its enzymatic degradation.
"Our findings will guide the kind of research to find drugs that enhance inhibition on auditory cortical neurons," Bao said. "There are a lot of things we can do to change GABA functions, some of which could potentially alleviate tinnitus with fewer side effects."
Provided by University of California - Berkeley
How do they determine that the ringing is not bothering the rats anymore ? Do they ask them ?
I would love to have this ringing stop, I had a rocket impact about 5 feet from me in Vietnam, followed up by bombing runs dropping 500 lbers a few hundred yards away. The ringing is sometimes so loud as to drown out other sounds, but most of the time just an irritating background neverending whine.
That’s not far from the truth. I have pretty bad tinnitus that I mostly ignore. In fact, as I was writing this post, my smartphone started doing something stupid and that distracted me so much that I began to ignore the ringing again.
Ringing since 03-08-68. Bouncing Betty in a railroad tunnel started the show and other events the rest of the year completed the concert. Kind of an irritant, but since that was the only lasting injury during my tour, I’m just happy to be alive to hear it.
For me, sometimes it's so loud I can't hear much else, like right now. At other times it's completely quiet, something some audiologists I've seen seem to have trouble believing.
Speaking of audiologists...I hate those hearing tests where you have to raise your hand or push a button when you hear the tone.
Most of the time, the ringing in my ears is the same frequency and MUCH louder than the hearing test tones.
I’m pushing 50, and mine started a few months ago. I’ve since had a hearing test, and have excellent hearing with no loss.
I’ve enjoyed shooting, home construction projects, and I’m a recent drummer. But I’m obsessive about hearing protection. The doc said my drumming didn’t cause it, and it’s hereditary.
Coincidentally, it started (I first noticed it) the first night after new cymbals were delivered, and I was testing them at limited volumes (I’m a flinching wimp when it comes to loud noises) without protection. I woke up and asked my wife if she left an alarm on or something, but it was just my ears (mostly right ear).
My theory is that it’s caused by 100% agave reposado tequila on the rocks with a squeeze of lime.
What you are describing is called "objective" tinnitus, where there is an actual physical source for the sound--blood flow, or some body process being picked by the ear. The article is discussing "subjective" tinnitus, where there is NO physical source for the sound. It's not an ear problem, but rather a brain problem. The article compared it to phantom limb syndrome.
LOL! As a lifelong tinnitus 'sufferer' myself, I wasn't thinking about or even noticing it until clicking on this thread ... now I've got a 13khz 'test tone' roaring thru my head ...
This article explains something that I’ve puzzeled over, to wit: why does a low-level white noise source help so much? It’s not really just distraction, it actually seems to lessen the volume. If these guys are right, it would make sense that having some sound input could turn some of the cells “off”, so the phantom noise actually subsides.
Whatever works though. It can be maddening.
Several years ago I went to a audiologist and he gave me some exercises to do with your jaw. Seem to calm the noise down a bit.
Can they also make the voices stop too?
You post some of the cutest/funniest pics for this topic.
:-)
Thanks Red Badger.
Two comments, GABA is awesome stuff! You WILL sleep! You may feel like Timoth Leary is in your bedroom with you, however. Wild dreams!
Also Whole Foods carries a supplement called “Clear Tinnitus”
www.clearproductsinc.com
Not a cure but it helps.
Good Luck! Still taking the chromium as well.
But then? the worst part was that the article really had nothing new to say!.
Why did they bother writing it? just to bother ordinary folk like us?
Thanks, Civ.
Oz never did give nothing to the tinnitus man...
Ping
That is a good description for the "VIVID dreams" that can be produced by some antidepressants also, which share some biochemical properties with GABA. If I weren't so lazy I'd do the letters of vivid in different rainbow colors and blinking.
My Dad has it, he also has hearing loss, and I think it interferes with his hearing aids. I have a periodic sound in my ear, but they have not diagnosed it as tinnitis. For the time being it only bothers me off and on (sounds more like a humming bird flying past my ear, with doppler effect and everything). My ear dr has no good explanation for it.
Only Van Halen? Piker.
Explosives, guns, several years in power plants, wood shop tools, no muffler lawn mower, many live concerts in front row, shop vacs, exploding bicycle tires...you name it. I’m surprised I can hear anything at all.
Oil can!
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