1High-field MR Centre, Max Planck Institute for Biological Cybernetics, Tbingen, Germany; 2Sir Peter Mansfield Magnetic Resonance Centre, University of Nottingham, Nottingham, United Kingdom; 3Department for Biomedical Magnetic Resonance Imaging, University of Tbingen, Tbingen, Germany
Gradient echo BOLD fMRI contrast was compared to the underlying local susceptibility changes, calculated from the same time-series using functional quantitative susceptibility mapping (fQSM). Comparing voxels coincidentally activated in both fQSM and GE-fMRI, differences were found between motor, visual and somatosensory paradigms in the respective brain areas. In most of these common voxels the signs of susceptibility and magnitude change were opposite confirming expectations. Yet, in a significant number of voxels the signs matched, suggesting strong non-local contributions. Experiments with the motor paradigm showed positive susceptibility shifts and magnitude signal changes in deep cortical layers.