Functional Magnetic Resonance Imaging Study of Brain Activation by Sound Localization in Artificial Unilateral Hearing Loss

抄録

Purpose : We aimed to identify brain activation on functional magnetic resonance imaging after a sound localization task in artificial unilateral hearing loss using an earplug.
Materials and Methods : Subjects were 16 healthy volunteers who were divided equally into the right hearing loss group (R group) and the left hearing loss group (L group). Sound stimuli were stereo and pure tone of 2000 Hz with varying right and left amplitude ratios. Using a block design, sound stimuli were randomly presented to the subjects every 2 sec into the task. We investigated the activation areas under conditions of normal hearing (NH) and artificial unilateral hearing loss (UHL). The analysis region was focused on the combined Heschl's and superior temporal gyri. In addition, the % signal change was calculated to examine hemispheric laterality of the hemisphere.
Results : In artificial unilateral hearing loss, significant activation in response to the sound localization task was observed in the hemisphere ipsilateral to the ear with hearing loss. The % signal change of the right hemisphere was significantly higher in the R group under UHL conditions and that of the left hemisphere was significantly higher in the L group under NH conditions. In the analysis of laterality index (LI) and LI of each individual after wearing the earplug, the shift of laterality was right predominance.
Conclusion : In an artificial acute-phase UHL, the ipsilateral combined Heschl's and superior temporal gyri showed significant activation in a sound localization task. The right hemisphere was suggested to be the dominant brain region associated with sound localization.