Why some people with hearing loss develop tinnitus – a buzzing or ringing sound in the ears in the absence of any real sound -and others don’t has puzzled scientists for years. Almost all cases of tinnitus are preceded by a loss of hearing as the result of damage to the inner ear from aging, injury, or long-term exposure to loud noise, but experts estimate that only a third of those with hearing loss will go on to develop tinnitus. That amounts to nearly 23 million American adults annually in the United States.
Researchers funded by an NIDCD challenge grant from the American Recovery and Reinvestment Act (ARRA) are suggesting a novel theory to explain why some people are more vulnerable to tinnitus than others. They propose that the limbic system – a linked network of brain structures involved in emotion, behavior, and long-term memory – acts as a gatekeeper to keep the tinnitus signal from reaching the auditory cortex, the part of the brain that mediates our conscious perception of sounds. In people with tinnitus, they suggest, the gate has broken. Their findings are published in the January 13, 2011, issue of Neuron.