For the first time, signals relating to tinnitus have been mapped out in the brain of a patient undergoing surgery.
The patient, a 50-year-old man suffering with intractable epilepsy, was showing signs of tinnitus but being monitored for two weeks to trace the cause of his epileptic seizures being opting for surgery. 164 electrodes were placed directly onto his brain and researchers compared brain activity when he heard loud ringing in his ears to when it was quieter, finding surprising differences spread across a wide set of brain areas.
Dr Phillip Gander from the University of Iowa in the US, said: “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.”
At the heart of the study is a method called “residual inhibition” used to manipulate tinnitus. Over the course of two days, researchers played a burst of noise for 30 seconds to the patient on some headphones. This was done on 60 occasions and for half of that time, the man’s tinnitus was quiet in the time immediately after the noise.
“Once we had that contrast between the normal tinnitus and the suppressed tinnitus trials… we could compare the brain activity between those two states,” co-author William Sedley, a doctor and neuroscientist at Newcastle University said. This comparison was able to show traces of tinnitus within the man’s brain.
Professor Andrew King, an auditory neuroscientist at Oxford University, described the findings as a “huge step up” in tracing the detailed underpinnings of tinnitus. However, he stressed that this is just a single case study and said tinnitus is “highly variable” between individuals.
“There are a lot of animal studies which look at what happens to individual neurons… but human work has largely been limited to fMRI,” he said.
“So this provides a step in between. It provides much higher resolution information about the changes that take place in the brain – albeit of this one individual – whilst tinnitus is being perceived.”
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