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Neuroimage. 2012 Aug 15;62(2):594-601. doi: 10.1016/j.neuroimage.2012.01.103. Epub 2012 Jan 28.

The coupling controversy.

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Department of Radiology, Research Imaging Institute, University of Texas Health Science Center at San Antonio, USA.


Functional magnetic resonance imaging (fMRI) relies on the well-known phenomenon of coupling between neuronal activity and brain blood flow. For nearly a century, the presumption was that hemodynamics were coupled to neuronal activity via energy demand and oxidative metabolism. Early (15)O positron-emission tomographic (PET) studies challenged this theory, demonstrating a physiological "uncoupling" between brain blood flow and oxygen metabolism. These PET observations played a pivotal role in guiding the development of fMRI, by demonstrating which physiological parameters were most closely coupled to neuronal activity and by presaging the BOLD-contrast effect. Subsequent PET studies were crucial for constraining theories concerning the physiological mechanisms underlying hemodynamic/neuronal coupling and, thereby, guiding the development of models for quantification of oxygen metabolic rate %∆ from fMRI. A first-person account of the PET "coupling" studies and their influence on the development of fMRI is provided.

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