Daniel A.
Handwerker1, Paula Wu1,2, Ronald M. Harper3,
Peter A. Bandettini1,4
1Section on Functional Imaging Methods,
National Institute of Mental Health, Bethesda, MD, United States; 2Neuroscience,
University of California, Los Angeles, Los Angeles, CA, United States; 3Neurobiology,
David Geffen School of Medicine, UCLA, Los Angeles, CA, United States; 4Functional
MRI Facility, National Institute of Mental Health, Bethesda, MD, United
States
Hypercapnia
creates global changes in cerebral blood flow, volume, and oxygenation that
can be measured with fMRI and used for calibration. Breath-holding is a
simple way to induce hypercapnia, but it may alter thoracic chest pressure
and include a ValSalva effect. We alter chest pressure while keeping the hold
duration constant to see how the BOLD signal changes. The initial BOLD
undershoot and following peak scale with pressure. Because the precise
contrast mechanisms behind these changes are not fully understood, they may
be a confound in calibration studies, or a novel way to rapidly induce calibration-useful
global BOLD signal changes.