Abstract #2078

Influence of the Choice of the Impulse Response Function in Statistical Analysis of Diffusion FMRI Time Series at High B-Value

Emilie Valle¹, Live Eikenes², Anders Kristoffersen³, Asta K. Hberg²,³

¹MI Lab, Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway; ²Department of Neuroscience, Norwegian University of Science and Technology, Trondheim, Norway; ³MI Lab, Department of Medical Imaging, St. Olavs Hospital, Trondheim, Norway

Diffusion functional MRI has been proposed as a method that detects true neuronal activity as changes in the grey matter diffusion properties. Due to the high level of noise present in the data, the origin of the diffusion signal remains uncertain. Data was analyzed using a response function modeling the diffusion process (DRF) and the vascular process (HRF). Though the average time-course from DRF analysis showed a 3s earlier and steeper rise than the one from HRF analysis (= BOLD signal), noise measurements suggested that the observed shift was caused by correlated noise (physiological and artefactual) present in the data.