Spatial and temporal resolution of functional magnetic resonance imaging

Functional magnetic resonance imaging has become an invaluable tool for cog nitive neuroscience, despite the fact that many of the physiological mechan isms giving rise to the effect are not well understood. We review the known biochemical and physiological basis of the technique and discuss how, with in the noted limits, one might fully exploit the spatial and temporal resol ution that is intrinsic to the very high magnetic fields that we use for hu man studies. This noninvasive brain mapping technique relies on the changes in blood oxygenation, blood volume, and blood flow, and we discuss some of the issues influencing the effects of these hemodynamic parameters on imag e intensity.