IOWA CITY, Iowa, April 24 (UPI) -- Ear ringing may seem like a minor problem, but incessant ringing in the ears -- the cause, usually unknown -- can be much more than a nuisance. It can be infuriating, even debilitating.
In an attempt to get to the bottom of this health mystery -- a problem known as tinnitus -- researchers at the University of Iowa use specialized invasive brain monitoring technology to locate and observe the brain networks responsible for phantom ear ringing in real time.
"Perhaps the most remarkable finding was that activity directly linked to tinnitus was very extensive and spanned a large proportion of the part of the brain we measured from," study co-author Will Sedley, a researcher at Newcastle University in England, said in a press release. "In contrast, the brain responses to a sound we played that mimicked [the subject's] tinnitus were localized to just a tiny area."
The monitoring technique is typically used during epilepsy surgery, but the technology proved vital to tracking the neurological origins of tinnitus.
"This has profound implications for the understanding and treatment of tinnitus, as we now know it is not encoded like normal sound, and may not be treatable by just targeting a localized part of the hearing system," said study author Phillip Gander, postdoctoral research scholar in Iowa's neurosurgery department.
The brain research lab at the University of Iowa is one of the few places in the world with the technology and know-how to do invasive brain monitoring. Because most epilepsy surgery patients volunteer to participate in ongoing studies, scientists at the lab are in a unique position to conduct exciting experimental research on neurological problems.
"We are putting a recording platform into the patient's brain for clinical purposes and we can modify it without changing the risk of the surgery," said Matthew Howard, who heads up Iowa's Human Brain Research Laboratory. "This allows us to understand functions in the brain in a way that is impossible to do with any other approach."
Even though 1 in 5 people deal with some form of tinnitus, however, it's not necessarily common for people needing epilepsy surgery to also experience significant bouts of phantom ear ringing.
"It is such a rarity that a person requiring invasive electrode monitoring for epilepsy also has tinnitus that we aim to study every such person if they are willing," Gander said.
To locate the source of tinnitus, researchers compared brain signals during weaker and stronger moments of ringing. They also looked at brain signals while the patient listened to an actual ring that mimicked the phantom sound.
Whereas actual sounds -- even those imitating phantom ringing -- produce brain activity in an especially contained and localized fashion, phantom ringing produces a vast network of brain stimulation.
"The sheer amount of the brain across which the tinnitus network is present suggests that tinnitus may not simply 'fill in the gap' left by hearing damage, but also actively infiltrates beyond this into wider brain systems," Gander explained.
The new research was published in the journal Current Biology.