Contribution of Different Sources of Signal Variance to T2* and S0 Maps in the Human Brain at Rest: A 7T Study

Marta Bianciardi¹, Masaki Fukunaga¹, Peter van Gelderen¹, Jacco A. de Zwart¹, Jeff H. Duyn¹

To exploit the increased BOLD-contrast available at 7T for fMRI-studies, it is crucial to identify the various noise-sources and their origin. We determined the contribution of non-thermal noise to fluctuations in BOLD-weighted-, T₂*- and S₀-signals in the visual cortex at 7T during rest. The following noise-sources were considered: low-frequency-drifts, effects related to the phase of physiological cycles and to changes in physiological rates, thermal-noise, and other sources, tentatively attributed to spontaneous-activity. Our findings show that low-frequency-drifts have a physiological-contribution, and that spontaneous-activity has an echo-time dependence. Effects related to physiological-cycles and their rates contributed both to T₂*- and to S₀-images.