The goal of functional magnetic resonance imaging is to establish where in the brain neural activity occurs (e.g., Fig. 1). Unlike electroencephalography (EEG) or magnetoencephalography (MEG), which directly record changes associated with neuronal firing, fMRI relies on the metabolic processes that accompany neural activity, and the associated changes in blood flow, to generate spatial maps that show where the neural activity is likely to occur in the brain (Fig. 1). Neurons consume oxygen and glucose when they are active, and because neither is stored in the cell, active neurons absorb oxygen and glucose from the surrounding capillary bed. This creates a local decrease in oxygenated blood and a corresponding increase in deoxygenated blood. To compensate this, there is an increase in regional cerebral blood flow (rCBF), which results in a large influx of oxygenated blood – far more than is needed to compensate for the decrease in oxygenated blood caused by...