FIG 1. FAIR maps of blood flow–related signal changes for a typical subject during repeated challenges of breath-holding for 40 seconds after inspiration (top) and for 30 seconds after expiration (bottom). The maps were generated by cross-correlation analysis with a boxcar reference waveform (correlation coefficients exceeding 0.41; P < .01) and a minimal cluster size of 5 pixels superimposed onto T1-weighted images. Areas of significant CBF-related signal changes during breath-holding are found mainly in gray matter.