Time-course of the auditory BOLD response to scanner noise

It is a concern for auditory fMRI studies that acoustic noise generated by the scanner produces an auditory response that can confound stimulus-induce d activation. To establish how to minimize this problem, the present study mapped the time-course of the auditory response to a burst of acoustic scan ner noise by employing a single-event method. Recorded bursts of scanner no ise were interspersed with clustered-volume acquisitions at a range of stim ulus-to-imaging delays to map the response with a temporal resolution of 1 sec. There were strong responses (1.5% signal change) to scanner noise in p rimary and secondary auditory cortex. In both cortical areas, the mean resp onse rose to a peak by 4-5 sec after stimulus onset and decayed after a fur ther 5-8 sec. The time course indicates that noise contamination in auditor y fMRI can be substantially reduced by using a 9-12-sec repetition time, th us maximizing the dynamic range available for displaying the response to ac oustical stimuli of interest. (C) 2000 Wiley-Liss, Inc.