Linear coupling of undershoot with BOLD response in ER-fMRI and nonlinear BOLD response in rapid-presentation ER-fMRI

► We found the correlation of the undershoot with the BOLD response in an ER paradigm. ► This voxelwise linear coupling supports a homogeneous hemodynamic response. ► The blood volume fraction was found to affect the BOLD response. ► We also studied the effect of nonlinear vascular response in a rapid ER paradigm. ► The effect might be accounted for by a scaling factor across the visual cortex.