Valerie E.M. Griffeth1, Nicholas P. Blockley2, Richard B. Buxton2
1Department of Bioengineering, University of California, San Diego, La Jolla, CA, United States; 2Department of Radiology, University of California, San Diego, La Jolla, CA, United States
We used a detailed model of the BOLD effect to reexamine the original assumptions of the Davis model for calibrated BOLD, particularly the relationship between the BOLD signal and the change in total deoxyhemoglobin content. A simple heuristic model, as an alternative to the Davis model, incorporates transparent dependency on the underlying physiology, and works remarkably well for CBF/CMRO2 coupling ratios from 1.3-5. Additionally, it directly defines the null line of the BOLD response while also providing a means by which to directly compare CBF/CMRO2 coupling ratios between two stimuli without calibrating to measure the scaling parameter, M.
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