Tinnitus and Chronic Pain Share a Common Brain Dysfunction

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iStock

Long after damage has occurred to a person’s hearing, some people still experience persistent tinnitus—the perception of a buzzing, ringing, or hissing sound—that can’t be accounted for by actual sounds. Remarkably, this phenomenon is very similar to bouts of chronic pain that persist after an injury has healed—and sometimes without the precursor of an injury.

Now researchers at Georgetown University Medical Center, in collaboration with Germany’s Technische Universität München, say they've identified a single brain dysfunction that causes both tinnitus and chronic pain. Their study, published in the journal Trends in Cognitive Sciences, revealed a common cause for these conditions, which affect 50 million (tinnitus) and 76.2 million (chronic pain) Americans alone. 

In a normally functioning brain, neural structures such as the nucleus accumbens, the ventromedial prefrontal cortex, and the anterior cingulate cortex act as “gatekeepers” to control noise, pain, and emotional signals and keep them from getting dysfunctional. In people who've suffered hearing loss, “the brain tries to reorganize and make the person hear as well as possible, but the side effect is that tinnitus noise is generated,” says Josef Rauschecker, one of the authors of the study. In people with tinnitus, these gatekeepers don't work as they should, letting through unwanted signals.

Strikingly, says Rauschecker, the brains of people who suffer from tinnitus have similar, measurable neural activity to those who suffer from chronic pain. In both cases this suggests that while there may be no external source of sound or pain—often referred to as “phantom pain”—the brain is receiving signals nonetheless.

“In tinnitus, the sound comes from the structures like the auditory cortex. It signals to the person that it’s a sound,” Rauschecker tells mental_floss. “It’s the same with chronic pain. There’s neuron activity in the brain’s pain system long after the injury has healed.”

Even more intriguing is the fact that those who suffer tinnitus or chronic pain also often suffer from depression or anxiety, says Rauschecker. This may stem from the fact that these brain structures also regulate emotions and interpret sensations. They do so via the nucleus accumbens, the brain’s reward and learning center, using the neurotransmitters dopamine and serotonin.

“The frontal cortex is part of the brain’s executive system—part of the limbic system—which regulates emotions. In tinnitus and chronic pain, we find that when these structures are impaired, there are fewer neurons and hyperactivity in the striatum that controls these emotions,” says Rauschecker. In essence, the brain is no longer able to turn down the volume, or incorrectly overemphasizes the signals, amplifying them and creating noise, pain, depression, or anxiety. 

While researchers don’t yet understand how these neural structures become broken, they are getting closer to understanding how the brain modulates—or fails to modulate—these signals. Now that they've identified the brain structures involved, their next line of research is learning how the neurotransmitters involved, such as glutamate, GABA, serotonin, and dopamine, play a role.

Through a variety of treatments, Rauschecker hopes they can learn to modulate the gatekeepers’ excessive reception and "turn down" signals of noise and pain to normal levels. "The ultimate goal is to get drug treatment and develop something that can mitigate this suffering," he says.

In the meantime, he suggests that we can all limit our potential to develop tinnitus by steering clear of excessively loud noises, or using earplugs and other means to reduce noise when possible. “Once you have tinnitus, it’s much harder to reverse.”

NASA Reveals How Living in Space for a Year Affected Scott Kelly’s Poop

NASA, Getty Images
NASA, Getty Images

When you agree to be part of a yearlong space study, you forfeit some right to privacy. In astronaut Scott Kelly’s case, the changes his body endured while spending a year at the International Space Station (ISS) were carefully analyzed by NASA, then published in a scientific journal for all to see. Kelly submitted blood samples, saliva samples, and cheek swabs. Even his poop was subjected to scrutiny.

As PBS reports, Scott Kelly’s fecal samples revealed that his gut microbiome underwent significant but reversible changes during his time in orbit. In what was surely good news for both Kelly and NASA, his gut bacteria didn’t contain anything “alarming or scary,” according to geneticist Martha Hotz Vitaterna, and it returned to normal within six months of landing on Earth.

Even after being subjected to the challenging conditions of space, “Scott’s microbiome still looked like Scott’s microbiome, just with a space twist on it,” said Vitaterna, who was one of the study’s authors.

The fecal probe was one small part of a sweeping NASA study that was just published in the journal Science, more than three years after Kelly’s return. Dubbed the Twins Study, it hinged on the results of Kelly’s tests being compared with those of his identical twin, retired astronaut Mark Kelly, who remained on Earth as the control subject.

NASA’s goal was to gain insight into the hazards that astronauts could face on proposed long-term missions to the Moon and Mars. The agency has gone to great lengths to get this information, including offering to pay people $18,500 to stay in bed for two months in order to replicate the conditions of anti-gravity.

It also explains why NASA was willing to launch unmanned rockets into space to collect samples of Kelly’s poop. On four different occasions at the ISS, Kelly used cotton swabs to pick up poo particles. When the rockets arrived to drop off lab supplies, they returned to Earth with little tubes containing the swabs, which had to be frozen until all of the samples were collected. The process was tedious, and on one occasion, one of the SpaceX rockets exploded shortly after it launched in 2015.

The study also found that his telomeres, the caps at the ends of chromosomes, had lengthened in space, likely due to regular exercise and a proper diet, according to NASA. But when Kelly returned to Earth, they began to shorten and return to their pre-spaceflight length. Shorter telomeres have a correlation with aging and age-related diseases. “Although average telomere length, global gene expression, and microbiome changes returned to near preflight levels within six months after return to Earth, increased numbers of short telomeres were observed and expression of some genes was still disrupted,” researchers wrote.

Researchers say more studies will be needed before they send the first human to Mars. Check out NASA's video below to learn more about what they discovered.

[h/t PBS]

Astronomers Want Your Help Naming the Largest Unnamed Dwarf Planet in the Universe

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iStock.com/jgroup

Part of the fun of becoming involved in science is naming things. Entomologists are notorious for branding new species of insects with fanciful names, like the Star Wars fans who labeled apoid wasps Polemistus chewbacca and Polemistus yoda. Sometimes scientists invite the public’s opinion, as in the 2016 petition by the UK's Natural Environment Research Council to have internet users name a polar research ship. They dubbed it Boaty McBoatFace. (That choice was overruled, and the ship is now known as the RRS Sir David Attenborough.)

Now, astronomers are looking to outsource the name of a dwarf planet. But the catch is that there’s no write-in ballot.

The planet, currently known as (225088) 2007 OR10, was discovered in 2007 in the Kuiper Belt orbiting the Sun beyond Neptune and may have a rocky, icy surface with a reddish tint due to methane present in the ice. It's bigger than two other dwarf planets in the Kuiper Belt—Haumea and Makemake—but smaller than Pluto and Eris.

The three astronomers involved in its identification—Meg Schwamb, Mike Brown, and David Rabinowitz of Caltech’s Palomar Observatory near San Diego, California—are set to submit possible names for the dwarf planet to the International Astronomical Union (IAU). They’ve narrowed the choices down to the following: Gongong, Holle, and Vili.

Gonggong, a Mandarin word, references a Chinese water god who is reputed to have visited floods upon the Earth. Holle is a German fairy tale character with Yuletide connotations, and Vili is a Nordic deity who defeated a frost giant.

The team is accepting votes on the planet’s website through 2:59 EDT on May 11. The winning name will be passed on to the IAU for final consideration.

[h/t Geek.com]

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