Microvascular GE BOLD Specificity and Dynamics Revealed by Ultra High Field MRI in Humans

Jeroen C. W. Siero¹, ², Nick F. Ramsey¹, Hans Hoogduin¹, ², Dennis W. J. Klomp², Peter R. Luijten², Natalia Petridou¹, ²

Gradient-echo BOLD at high fields has opened up the possibility to visualize the cortical columnar and laminar functional organization but its specificity can suffer from contributions of several vessel sizes even at high fields. Here we assess the microvascular contributions of the GE BOLD response (HRF) across the cortical depth at 7T by relating it to the microvascular specific SE BOLD response. We show that the early phase (onset time and rising slope) of the GE HRF is specific to the microvasculature in deep gray matter which presumably contains layers III-V.