Comparison of continuous sampling with active noise cancellation and sparse sampling for cortical and subcortical auditory fMRI

Purpose: Detecting sound-related activity using fMRI requires the auditory stimulus to be more salient than the intense background scanner acoustic noise. Various strategies can reduce the impact of scanner acoustic noise including “sparse” temporal sampling with single/clustered acquisitions providing intervals without any background scanner acoustic noise, or active noise cancellation (ANC) during “continuous” temporal sampling which generates an acoustic signal that adds destructively to the scanner acoustic noise substantially reducing the acoustic energy at the participant’s eardrum. Further, multiband fMRI allows multiple slices to be collected simultaneously, thereby reducing scanner acoustic noise in a given sampling period. Methods: 1.5mm isotropic multiband fMRI with sparse sampling (effective TR 9,000ms, acquisition duration 1,962ms) and continuous sampling (TR 2,000ms) with ANC were compared in 15 normally hearing participants. A sustained broadband noise stimulus was presented to drive activation of both sustained and transient auditory responses within subcortical and cortical auditory regions Results: Robust broadband noise-related activity was detected throughout the auditory pathways. Continuous sampling with ANC was found to give a statistically significant advantage over sparse sampling for the detection of the transient (onset) stimulus responses particularly in auditory cortex (p<0.001) and inferior colliculus (p<0.001), whereas gains provided by sparse over continuous ANC for detecting offset and sustained responses were marginal (p~0.05 in superior olivary complex, inferior colliculus, medial geniculate body, and auditory cortex). Conclusions: Sparse and continuous ANC multiband fMRI protocols provide differing advantages for observing the transient (onset and offset) and sustained stimulus responses.