title: Caffeine reduces the initial dip in the visual BOLD response at 3 T.
abstract: Localized changes in oxygen consumption related to increased neural activity can result in a small and transient "initial dip" of the blood oxygenation level-dependent (BOLD) signal used in functional magnetic resonance imaging (fMRI). The initial dip has been of great interest to the fMRI community because it may provide a more accurate and localized measure of neural activity than the conventional BOLD signal increase. Although potentially useful as a technique for human brain mapping, the initial dip is not always detected and has been a source of some controversy. In this study, the BOLD response to a 4-s long visual stimulus was measured with a 3-T MRI system in 5 healthy volunteers both before and immediately after a 200-mg oral caffeine dose. The caffeine dose significantly (P < 0.001) reduced or eliminated the initial dip in all subjects. These findings suggest that caffeine usage may be a key factor in the detection of the initial dip in human fMRI studies.
authors.affiliation: Center for Functional Magnetic Resonance Imaging and Department of Radiology, University of California-San Diego, 9500 Gilman Drive, La Jolla, MC 0677, CA 92093-0677, USA.
authors.forename: Yashar
authors.initials: Y
authors.lastname: Behzadi
authors.forename: Thomas T
authors.initials: TT
authors.lastname: Liu
mesh_terms: D000328:Adult; D001628:Beverages; D002110:Caffeine / Q000494:pharmacology*; D002560:Cerebrovascular Circulation / Q000187:drug effects / Q000502:physiology*; D003069:Coffee; D006801:Humans; D007700:Kinetics; D008279:Magnetic Resonance Imaging; D010100:Oxygen / Q000097:blood*; D013662:Tea
chemical_list: D003069:Coffee; D013662:Tea; D002110:Caffeine; D010100:Oxygen