Valerie E M Griffeth1, Nicholas P. Blockley2, Aaron Simon3, Richard B. Buxton4
1Bioengineering, University of California San Diego, La Jolla, CA, United States; 2FMRIB, University of Oxford, Oxford, United Kingdom; 3Bioengineering, University of California, San Diego, La Jolla, CA, United States; 4Radiology, University of California San Diego, La Jolla, CA, United States
The simple and straightforward ratio method can be used test whether the CBF-CMRO2 coupling ratio is the same for two different stimulus responses using only combined CBF and BOLD measurements, independent of model parameters, and without an additional calibration experiment. We tested the ratio method using a previously published detailed BOLD model demonstrating that it is an effective approach for comparing stimulus responses in order to differentiate between values of CBF-CMRO2 coupling. We also include a reanalysis of recently published data on varying visual stimulus contrast showing consistency of these results in comparison to the traditional Davis model approach.