About one in five people experience tinnitus, the perception of a sound, often described as ringing, that isn’t really there. Now, an opensource study in the journal Current Biology, has taken advantage of a rare opportunity to record directly from the brain of a person with tinnitus in order to find the brain networks responsible.  The observations reveal just how different tinnitus is from normal representations of sounds in the brain.

The team, from The University of Iowa and Newcastle University state that 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 that was recorded from.  In contrast, the brain responses to a sound the researchers played that mimicked the subject’s tinnitus were localized to just a tiny area.

In the current study the team contrasted brain activity during periods when tinnitus was relatively stronger and weaker. The study was only possible because the 50-year-old patient they studied required invasive electrode monitoring for epilepsy. The subject also happened to have a typical pattern of tinnitus, including ringing in both ears, in association with hearing loss.  The researchers explain that it is such a rarity that a person requiring invasive electrode monitoring for epilepsy also has tinnitus that the medical community aim to study every such person if they are willing.

The data findings showed the expected tinnitus-linked brain activity, however, the results showed that the unusual activity extended far beyond circumscribed auditory cortical regions to encompass almost all of the auditory cortex, along with other parts of the brain.  The discovery adds to the understanding of tinnitus and helps to explain why treatment has proven to be such a challenge, the researchers say.

The team state that the medical community now knows that tinnitus is represented very differently in the brain to normal sounds, even ones that sound the same, and therefore these cannot necessarily be used as the basis for understanding tinnitus or targeting treatment.  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, the researchers add.

These new insights may help to inform treatments such as neurofeedback, where patients learn to control their brainwaves, or electromagnetic brain stimulation, according to the researchers. The team surmise that a better understanding of the brain patterns associated with tinnitus may also help point toward new pharmacological approaches to treatment, which have so far generally been disappointing.

Source:   The University of Iowa