Abstract #0721

Anticorrelated FMRI Signal Changes of Hemodynamic Origin in Large Cerebral Vessels

Molly Gallogly Bright¹,², Marta Bianciardi²,³, Jacco A. de Zwart², Jeff H. Duyn²

¹CUBRIC, School of Psychology, Cardiff University, Cardiff, United Kingdom; ²Advanced MRI Section, LFMI, NINDS, National Institutes of Health, Bethesda, MD, United States; ³A.A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, United States

Negative fMRI signal changes have been observed in large cerebral vessels, and modeling suggests this phenomenon originates from changes in blood volume rather than deoxyhemoglobin concentration. To better understand the underlying mechanisms, respiratory challenges were used to create transient hypocapnia and global decreases in blood volume in 10 subjects during BOLD-weighted EPI acquisition at 7 Tesla. The global timeseries was correlated with every voxel, and the time-to-peak of the voxelwise response was extracted. Large vessels exhibited anticorrelated signal changes of physiological origin that occurred significantly earlier than the response across gray matter, suggesting early blood volume changes are responsible.