Decay-sampling design for echo-planar functional Magnetic Resonance Imaging (fMRI) of the auditory cortex

The main limiting factor to the application of the functional Magnetic Resonance Imaging (fMRI) to the study of the auditory cortex is the presence of the loud background acoustic noise in the MR scanner during functional measurements. In the present work, we propose an averaged single-trial experimental design for EPI-fMRI (decay-sampling design) which does not require the presentation of stimuli during echo-planar acquisitions and allows for mapping of auditory cortex without the interference of scanner noise. We apply the decay-sampling technique to the study of the cortical responses to amplitude modulated tones in healthy volunteers. Results point out the presence, within the auditory cortex, of neuronal clusters that correspond to different models of responses to the stimulus and to the EPI noise. Furthermore, some of these clusters show a clear tonotopic organization.