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Brain Res. 2009 Dec 22;1304:129-37. doi: 10.1016/j.brainres.2009.09.089. Epub 2009 Sep 28.

Auditory cortex stimulation by low-frequency tones-an fMRI study.

Author information

1
Department of Neuroradiology, Charité-Universitary Medicine Berlin, Charitéplatz 1, 10117 Berlin, Germany. Esther.dommes@charite.de

Abstract

BACKGROUND AND PURPOSE:

Low-frequency tones (LFT) and infrasound (IS) are looked upon as potentially hazardous to human health. We aimed at assessing LFT/IS-induced activation of the auditory cortex by using fMRI.

MATERIALS AND METHODS:

fMRI was used to investigate LFT/IS perception in 17 healthy volunteers. Short tone bursts of 12, 36, 48 and 500 Hz were delivered directly into the right external ear canal through a 12-m long silicone tube and an ear plug. Sound pressure levels (SPL) and spectral analysis of the stimuli and scanner noise were measured in situ by using a metal-free optical microphone and a fiber-optic cable.

RESULTS:

SPL-dependent activation of the superior temporal gyrus, i.e. Brodmann areas (BA) 41 and 42 as well as BA 22, was delineated subsequent to acoustic stimulation with 12-, 48- and 500-Hz stimuli. Thresholds for LFT/IS-induced brain activation were between 110 and 90 dB SPL in normal hearing subjects. Spectral analysis revealed the occurrence of harmonics together with LFT, of which 36-Hz harmonics interfered with IS exposure at 12 Hz as well as scanner noise.

CONCLUSION:

Our results provide evidence that auditory cortex activation may be induced by LFT/IS exposure, depending on sound pressure levels applied. Clinical implications of our findings will have to be addressed by subsequent studies involving patients presumptively suffering from LFT-dependent disorders.

PMID:
19796632
DOI:
10.1016/j.brainres.2009.09.089
[Indexed for MEDLINE]

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