What We Can and What We Can’t Do with fMRI

Functional activation of the brain can be detected with magnetic resonance imaging (MRI) by directly measuring tissue perfusion, blood-volume changes, or changes in the concentration of oxygen. The latter blood oxygenation level–dependent (BOLD) contrast mechanism (Logothetis, 2003; Logothetis and Wandell, 2004; Logothetis, 2008) is currently the mainstay of human neuroimaging. The interpretation of fMRI signals in brain research, and by extension, the utility of fMRI, critically depends on factors such as signal specificity and spatial and temporal resolution. Signal specificity ensures that the generated maps reflect actual neural changes, whereas spatial and temporal resolution determine our ability to discern the elementary units of the activated networks and the time course of various neural events