title: Modeling hemodynamic responses in auditory cortex at 1.5 T using variable duration imaging acoustic noise.
abstract: A confound for functional magnetic resonance imaging (fMRI), especially for auditory studies, is the presence of imaging acoustic noise generated mainly as a byproduct of rapid gradient switching during volume acquisition and, to a lesser extent, the radiofrequency transmit. This work utilized a novel pulse sequence to present actual imaging acoustic noise for characterization of the induced hemodynamic responses and assessment of linearity in the primary auditory cortex with respect to noise duration. Results show that responses to brief duration (46 ms) imaging acoustic noise is highly nonlinear while responses to longer duration (>1 s) imaging acoustic noise becomes approximately linear, with the right primary auditory cortex exhibiting a higher degree of nonlinearity than the left for the investigated noise durations. This study also assessed the spatial extent of activation induced by imaging acoustic noise, showing that the use of modeled responses (specific to imaging acoustic noise) as the reference waveform revealed additional activations in the auditory cortex not observed with a canonical gamma variate reference waveform, suggesting an improvement in detection sensitivity for imaging acoustic noise-induced activity. Longer duration (1.5 s) imaging acoustic noise was observed to induce activity that expanded outwards from Heschl's gyrus to cover the superior temporal gyrus as well as parts of the middle temporal gyrus and insula, potentially affecting higher level acoustic processing.
authors: School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, USA. hu@ecn.purdue.edu
authors: Shuowen
authors: S
authors: Hu
authors: Olumide
authors: O
authors: Olulade
authors: Javier Gonzalez
authors: JG
authors: Castillo
authors: Joseph
authors: J
authors: Santos
authors: Sungeun
authors: S
authors: Kim
authors: Gregory G
authors: GG
authors: Tamer
authors: Wen-Ming
authors: WM
authors: Luh
authors: Thomas M
authors: TM
authors: Talavage
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods*; D001303:Auditory Cortex / Q000502:physiology*; D001783:Blood Flow Velocity / Q000502:physiology; D001931:Brain Mapping / Q000379:methods; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003198:Computer Simulation; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008954:Models, Biological; D009622:Noise