Brain MR signal has been observed to decrease during cessation of breathing due to the increase of deoxyhemoglobin in the blood. However, for both animal and human studies, we have demonstrated that if the subjects breathed 100% oxygen in advance of apnea for a short time, T2*-weighted MR brain signal increased when breathing was stopped for a period of 30-60 s. This demonstrates the possibility of measuring responses to hemodynamic change throughout the entire brain with a single respiratory perturbation in a rapid, reliable, and robust manner.