For the very first time, accurate measurements have been made of activity in the areas of the human brain connected with tinnitus (‘ringing in the ears’). Using innovative measuring and analysis technology, hearing researcher Dave Langers from the ENT department of UMCG managed to conduct a study of the brain’s sensitivity to pitch in people both with and without tinnitus. His research shows that sensitivity to pitch in tinnitus patients does not deviate demonstrably from that of people with normal hearing. This is a new concept that contradicts a number of existing ideas about sound processing in the brain, both in people with normal hearing and in tinnitus patients. It means that the cause of tinnitus is not what had been assumed up until now. Articles about Langer’s research are being published in this month’s editions of the scientific magazines Cerebral Cortex and Frontiers in Systems Neuroscience.
Tinnitus, also known as ‘ringing in the ears’, is a common hearing disorder whereby patients have a subjective perception of sound (usually a high pitch) in silent surroundings. Although not a life-threatening condition, tinnitus can have serious implications for day-to-day life. Unfortunately, no satisfactory treatment has yet been found. Tinnitus is usually assumed to be caused by spontaneous abnormal activity in areas of the brain used for processing certain tones.
Sound is processed in a number of auditory areas of the brain. Measurements recorded in chimpanzees show that these areas are arranged into sub-areas in which low and high-pitched sounds are processed separately, according to a principle known as tonotopy. Due to the limitations of available technology, it had been difficult to demonstrate or analyze the tonotopic organization of the human brain in any detail. However, over the last two years, a number of researchers from different countries have managed to make detailed and straightforward analyses of sensitivity to pitch in the auditory cortex.
The research carried out in Groningen was unique because it studied people with normal hearing as well as tinnitus patients. On the basis of existing theories, it had been assumed that the high-pitch areas of the brain in tinnitus patients would be excessively sensitive, thereby disturbing the tonotopic representation. However, this was not directly proved. Strangely enough, the new readings showed no significant difference: sensitivity to high-pitched sounds in tinnitus patients did not vary demonstrably from that of people with normal hearing. This shows that tinnitus does not necessarily go hand in hand with major tonotopic reorganization. Current models relating to the cause of tinnitus will therefore need to be modified. Although this research has not led to any new treatment options, it does have implications for experimental therapies being developed around the world aimed at restoring the tonotopic organization in tinnitus patients. Plans are currently being drawn up for follow-on research in the UMCG to see whether reorganization of this kind actually plays a role in the majority of tinnitus patients, who also suffer from an associated loss of hearing.
The study of people with normal hearing will shortly be published in the renowned journal Cerebral Cortex and is currently available online in a pre-publication version (http://dx.doi.org/10.1093/cercor/bhr282); the research among tinnitus patients was recently published in Frontiers in Systems Neuroscience (http://dx.doi.org/10.3389/fnsys.2012.00002).
For more information, please contact the press information department of UMCG, which can be reached on telephone number +31 (0)50 361 22 00.
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