Table 2. Means and standard deviations of HRI values calculated from all healthy subjects.

	GM	WM	GM/WM
ΔS-O2	2.54±0.63	0.71±0.30	3.84±1.01
ΔS-CO2	1.33±0.33	0.40±0.24	3.69±0.98
VRM	0.50±0.15	0.22±0.10

ΔS = percent signal intensity changes; GM = gray matter; WM = white matter; VRM = vascular reactivity mismatch.