Strictly speaking, fMRI machines measure the blood's oxygen level through a technique called blood oxygenation level-dependent (BOLD) contrast. The BOLD fMRI signal is supposedly related to blood changes, which are supposedly related to local metabolic changes, which are supposedly related to changes at the neuronal population activation level. These activation changes are presumably associated with changes in neural information processing. "Almost all of those links are at least under-specified at the moment," says Michael Young, director of the Institute of Neuroscience, University of Newcastle upon Tyne, and a longtime investigator of the relationship between fMRI signals and neuronal information processing.
Young and other fMRI researchers have applauded the recent study as a technical triumph and an important first step toward a much better understanding of fMRI signals. Study leader Nikos Logothetis, director of the physiology of cognitive processes group at Max Planck, and his collaborators, spent years constructing a magnet ...
