The possible role of oxygen metabolism in supporting brain activation remains elusive. We have used a newly developed neuroimaging approach based on high-field in vivo 17O magnetic resonance spectroscopic (MRS) imaging to noninvasively image cerebral metabolic rate of oxygen (CMRO2) consumption in cats at rest and during visual stimulation. It was found that CMRO2 increases significantly (32.3%±10.8%, n=6) in the activated visual cortical region as depicted in blood oxygenation level dependence functional maps; this increase is also accompanied by a CMRO 2 decrease in surrounding cortical regions, resulting a smaller increase (9.7%±1.9%) of total CMRO2 change over a larger cortical region displaying either a positive or negative CMRO2 alteration. Moreover, a negative correlation between stimulus-evoked percent CMRO2 increase and resting CMRO2 was observed, indicating an essential impact of resting brain metabolic activity level on stimulus-evoked percent CMRO2 change and neuroimaging signals. These findings provide new insights into the critical roles of oxidative metabolism in supporting brain activation and function. They also suggest that in vivo 17O MRS imaging should provide a sensitive neuroimaging modality for mapping CMRO2 and its change induced by brain physiology and/or pathologic alteration.
- Brain activation
- Cerebral metabolic rate of oxygen
- Functional MRI
- Imaging CMRO
- In vivo O MRS