Abstract
Background: Noise pollution has been called an invisible killer. It has been a critical issue for the people working in the noisy environments especially in industry and education. This study was conducted to evaluate the differences of neuronal activity between groups, an experimental group is profession in occupational noise environments and a control group is who did not, and all of the subjects had tinnitus or hyperacusis. We used the electroencephalography data from 17 patients. The two experimental subjects were a tinnitus patient and a hyperacusis patient. The fifteen control subjects were seven tinnitus and eight hyperacusis patients and all of the subjects had normal hearing.Results: We compared the brain activity for three states among the groups: after noise-induced state and no sound exposure state for the two experimental subjects, and no sound exposure state for the control group. The activity of the auditory cortex in the experimental group after noise exposure were significantly increased in gamma (p = 0.002) and decreased in delta and theta band. In other brain areas, the rates of the delta, theta, beta 1~3 and gamma for the control group were higher than the experimental subjects for both with or without noise exposure states.Conclusions: Through this study, it was suggested that the professions of tinnitus and hyperacusis with normal hearing in occupational noise environment could be maintain their pathological states by abnormal hyper-activation of the primary and secondary auditory cortex alone.
Specialization of primary auditory cortex processing by sound exposure in the "critical period"
