40 million people in the U.S. are currently suffering from tinnitus which seems to have no effective treatment. Well, a detailed insight into the ailment can supposedly help design appropriate treatments. Neuroscientists from the Georgetown University Medical Center (GUMC) claim that tinnitus is triggered by a confluence of structural and functional alterations in the brain. Similar process may also be responsible for chronic pain and other perceptual disorders.
With the help of fMRI, scientists tested 22 volunteers, half of whom had been diagnosed with chronic tinnitus. The primary and posterior auditory cortices of tinnitus patients possibly have moderate hyperactivity, but the nucleus accumbens shows the greatest degree of hyperactivity. This hyperactivity may be specific to sounds that were matched with frequencies lost in patients. The nucleus accumbens, a part of the corticostriatal circuit, seems to be involved in evaluation of reward, emotion, and unwillingness.
Josef P. Rauschecker, Ph.D., a neuroscientist, remarked, “This suggests that the corticostriatal circuit is part of a general ‘appraisal network’ determining which sensations are important, and ultimately affecting how or whether those sensations are experienced. In this study, we provide evidence that these limbic structures, specifically the nucleus accumbens and the ventromedial prefrontal cortex, do indeed differ in the brains of individuals with tinnitus.”
Functional lapses in these same areas reportedly have been implicated to altered mood states and chronic pain. Both of these conditions are apparently included in the inability to curb unwanted sensory signals. It was concluded that tinnitus can be understood, on examining the way auditory and limbic systems interact to influence perception.
The study is published in the January 13th issue of Neuron.