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The effect of MR scanner noise on auditory cortex activity using fMRI
Carrie J Scarff1, Joseph C Dort, Jos J Eggermont
1Behavioural Neuroscience Research Group, Department of Psychology, University of Calgary, Calgary, Alberta, Canada. carrietobolski@yahoo.com
Human Brain Mapping
|June 18, 2004
Summary
MR scanner noise significantly impacts auditory functional magnetic resonance imaging (fMRI) studies. This noise affects loudness perception and auditory cortex tonotopy, crucial for understanding brain responses to sound.
Area of Science:
- Neuroscience
- Auditory Neuroscience
- Neuroimaging
Background:
- Auditory functional magnetic resonance imaging (fMRI) studies are essential for mapping brain activity.
- Echo planar imaging (EPI) sequences used in fMRI generate significant acoustic noise, potentially confounding results.
- The precise impact of scanner noise on psychophysical measures and tonotopic mapping within the auditory cortex requires quantification.
Purpose of the Study:
- To investigate the influence of MR scanner noise on loudness perception.
- To assess the effect of scanner noise on tonotopic representations in the auditory cortex.
- To determine how scanner noise interacts with auditory stimuli at different frequencies.
Main Methods:
- Seven normal-hearing adults participated in the study.
- Participants were exposed to pure tones of five different frequencies (250–4,000 Hz) at equal loudness.
- Auditory fMRI was conducted using two imaging protocols with peak scanner noise at 1,460 Hz and 2,080 Hz, respectively.
- Psychophysical loudness judgments and fMRI BOLD responses were measured.
Main Results:
- Loudness perception and fMRI activity for tones near the peak scanner noise frequency were reduced compared to other frequencies.
- A 1-kHz tone showed reduced perception and fMRI activity when peak scanner noise was at 1,460 Hz.
- A 2-kHz tone showed reduced perception and fMRI activity when peak scanner noise was at 2,080 Hz.
- fMRI activity generally decreased with increasing stimulus frequency.
Conclusions:
- MR scanner noise directly affects psychophysical loudness perception and fMRI measures of auditory cortex tonotopy.
- Reduced fMRI activity near scanner noise frequencies may result from inflated scanner-induced baseline noise.
- Findings highlight the need to consider scanner noise when interpreting auditory fMRI data, especially for tonotopic mapping.