Revisit Nonlinearity in Blood-Oxygenation-Level-Dependent Signal

Nanyin Zhang¹, Essa Yacoub¹, Xiao-Hong Zhu¹, Kamil Ugurbil¹, Wei Chen¹

Literature studies suggest that there are significant nonlinear characteristics in the BOLD signal in response to evoked neuronal activity. We demonstrated previously that when eliminating contributions from large vessels, the nonlinearity in the BOLD signal becomes much less significant. In this study we have investigated (non)linear characteristics of the BOLD signal from the microvasculature using a combination of SE fMRI and a paired-stimulus paradigm. We found that that SE BOLD signal acquired at high magnetic fields, which is sensitive mainly to the microvasculature, is primarily a linear system.