[Article] Investigating mechanisms of fast BOLD responses: The effects of stimulus intensity and of spatial heterogeneity of hemodynamics
Summary: Many studies had reported that fast fMRI can track neural activity well above the temporal limit of the canonical HRF model but the biophysical mechanisms under those techniques were not much investigated. In this study, they use visual and somatosensory tasks with simultaneous EEG-fMRI data to show the difference of the HRF’s timing and shapes by the differences of the stimulus intensity. Secondly, they show that as the spatial resolution of fMRI increases, voxel-wise HRFs begin to deviate from the canonical model, with a considerable portion of voxels exhibiting faster temporal dynamics than predicted by the canonical HRF.