Brain activation in patients with idiopathic hyperacusis.

The neural network associated with idiopathic hyperacusis is still not well known. We studied the brain activation of 3 middle-aged patients with mild to moderate hyperacusis by functional magnetic resonance imaging while they were listening to white noise binaurally. In addition to the temporal lobes, in all patients, sound elicited activation in the frontal lobes (superior, middle, or inferior frontal gyri) and occipital lobes (precuneus, cuneus, superior occipital gyrus, lingual gyrus, or fusiform gyrus). The parahippocampus was activated in 2 of 3 patients. Furthermore, the precentral and postcentral gyri, superior and inferior parietal lobules, thalamus, midbrain, claustrum, insula, posterior cingulated gyrus, and orbital and rectal gyrus were also activated in one patient. The neural network associated with idiopathic hyperacusis might be associated with the frontal lobes and parahippocampus.

Hemispheric difference in activation patterns of human auditory-associated cortex: an FMRI study.

The purpose of this study was to demonstrate interhemispheric differences in activation patterns of the auditory-associated cortex elicited by a series of sounds. Functional magnetic resonance imaging was performed while different sounds were presented binaurally to 10 healthy subjects with normal hearing. Characteristic activation patterns were elicited although variability was shown between subjects. The activation number was significantly higher on the right than on the left side for non-speech (but not for speech) stimulations. As stimulation increased in complexity (from a pure tone to white noise to ocean wave sounds to classical music), the activation pattern of the superior temporal lobe became more pronounced in both hemispheres while that of the auditory cortex tended to become more sustained and concentrated on the right rather than on the left side. No hemispheric differences in activation pattern were seen in response to speech.