Table II.

Errors in the estimation of activation %ΔCMRO₂ with calibrated‐BOLD, using recent experimental measurements of CBF and BOLD responses to hypercapnia and activation

Study	Brain region	Hypercapnia		Activation		Estimated ΔCMRO2 (%)a		%ΔCMRO2 %ΔCBF
		ΔCBF (%)	ΔBOLD (%)	ΔCBF (%)	ΔBOLD (%)	δCO2 = 0	δCO2 = −0.11	δCO2 = 0	δCO2 = −0.11
Perthen et al., 2008	Visual cortex	48	2.6	48	1.2	18.5	14.0	0.39	0.29
Ances et al., 2008	Visual cortex	71	2.08	78	0.89	32.5	28.4	0.42	0.36
Ances et al., 2008	Basal ganglia	42	1.52	32	0.13	20.3	19.6	0.64	0.61
Leontiev et al., 2007	Visual cortex	66	2.52	82	1.81	21.5	13.6	0.26	0.17

^aCalculated from the Davis model [Eq. (1)] with the assumption that the fractional change in CMRO₂ with hypercapnia is δ_CO2. The standard assumption is δ_CO2 = 0, and the calculations were repeated assuming that the fractional decrease in CMRO₂ is identical to the observed fractional decrease in MEG power in the gamma band (δ_CO2 = −0.11).