Tinnitus is a condition in which patients experience a ringing sound that doesn’t really exist, and by understanding its mechanisms scientists may improve the lives of people who suffer from this often debilitation condition, affecting one in five people.
Both US and UK scientists completed a study that evaluated recordings taken from the brain of a 50-year-old man who was preparing for surgery to treat epilepsy. The man agreed to volunteer for the tinnitus study, creating a rare opportunity for scientists to study both conditions at the same 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,” said study co-leader Will Sedley of Newcastle University in the UK. “In contrast, the brain responses to a sound we played that mimicked (the subject’s) tinnitus were localized to just a tiny area.”
Study co-leader Phillip Gander, a postdoctoral research scholar in the neurosurgery department at the University of Iowa, added: “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.”
In the study, the researchers contrasted brain activity during periods when tinnitus was stronger and weaker, and found the expected tinnitus-linked brain activity. but were surprised to discover that the activity extended to encompass almost the entire auditory cortex, along with other parts of the brain. This was a much greater area than expected.
“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 said.
The new information may advance treatments known as neurofeedback, in which patients learn to control their “brainwaves,” or electromagnetic brain stimulation. A better understanding of the brain patterns associated with tinnitus may also guide new pharmacological approaches to treatment.
The findings were published in Current Biology.