Changes in Arterial Oxygen Tension with Evoked Stimulation in the Rat Somato-Sensory Cortex: Implications for Quantitative FMRI

Alberto L. Vazquez¹, Mitsuhiro Fukuda¹, Seong-Gi Kim¹

In an effort to investigate the changes in vascular and tissue oxygenation with evoked brain function, arterial, tissue and venous oxygen tension (and saturation) were measured in the rat somato-sensory cortex using oxygen micro-electrodes. Significant increases in the oxygen tension and saturation of pre-penetrating pial arterioles were observed. The largest increases in oxygen saturation were observed at the sampled small emerging pial veins. The observed steep oxygen tension and saturation gradient indicates that the quantification of the relative changes in CMRO2 from high-resolution BOLD fMRI data (hundreds of microns) will be underestimated.