Simultaneous quantification of oxygen and glucose consumption during visual stimulation in the human cortex

The brain relies on oxidized glucose as its primary fuel. Despite robust coupling of cerebral oxygen and glucose consumption during rest, the oxygen to glucose index (OGI) has been suggested to drop significantly during neuronal activation. However, empirical evidence regarding the extent of this uncoupling is scarce, mainly due to the inability of previous studies to measure CMRO2 and CMRglc concurrently during tasks. Therefore, in the present study, we integrated multiparametric quantitative BOLD (mqBOLD) with functional PET (fPET) to simultaneously quantify cerebral oxygen and glucose metabolism during visual stimulation and rest within a single session. Results show increases in both CMRO2 and CMRglc in visual areas, concomitant with focal blood flow increases. Moreover, OGI values during rest were close to the theoretical value of 6, which is in line with previous literature. In response to visual stimulation, the OGI decreased by 6.6-21.6%, depending on the mask applied. For the first time, the present study demonstrates the feasibility of combining mqBOLD and fPET to study CMRO2 and CMRglc simultaneously. This setup has the potential to be applied to various experimental settings, providing valuable information about the extent of oxidative glucose metabolism in the human brain under different conditions in health and disease.