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Zusammenfassung:
Cerebral metabolic rate of oxygen (CMRO2) can be obtained with magnetic resonance imaging (MRI) by calibrating BOLD using hypercapnia. CO2 administration influences BOLD by increasing and eventually stabilizing blood flow and volume respectively. This leaves blood oxygenation as the predominating (if not the only) factor affecting the magnitude of BOLD. Obviously, the above assortment implies that CO2 increase acts exclusively as vasoactive agent, without affecting neuronal activity and hence oxygen metabolism. Amongst others, the latter assumption was strengthened by the results of Schmidt and Kety in the 50s. Most of the fMRI studies report coupling of cerebral blood flow (CBF) and oxygen metabolism (the ratio of fractional changes in CBF and CMRO2 is n = 2). In this study we investigated the dependence of neural activity on enhanced CO2 concentration by means of simultaneous intracortical recordings and BOLD imaging in the anesthetized macaque monkey.
