BRAIN IMAGINGThe variability of serial fMRI data Correlation between a visual and a motor taskWaldvogel, Daniel1; Gelderen, Peter van2; Immisch, Ilka1; Pfeiffer, Christopher1; Hallett, Mark1,3Author Information 1Human Motor Control Section, NINDS, NIH, Building 10, Room 5N226, 10 Center Drive, MSC-1428, Bethesda, MD 20892–1428 2In Vivo NMR Research Center, NINDS, NIH, Building 10, 10 Center Drive, Bethesda, MD 20892, USA 3Corresponding author: Mark Hallett Acknowledgements: The authors appreciate the skillful editing of Devera G. Schoenberg, M.Sc. Received 19 July 2000; accepted 28 September 2000 NeuroReport: November 27, 2000 - Volume 11 - Issue 17 - p 3843-3847 Buy Abstract We investigated whether the intersession variability of serial fMRI studies correlates between two activation modalities, i.e. a standardized visual and a standardized motor task. Six volunteers were scanned in at least weekly intervals. The number of pixels activated as well as the activation amplitude varied widely. The maximal difference of the number of pixels activated was 1150%, of the activation amplitude 250%. In three volunteers, the variability was highly correlated between the two tasks. Three other volunteers showed one outlier each. We conclude that the intersession variability is due to global factors affecting the whole brain, but that due to unpredictable outliers, using a standardized task to normalize the data of interest is of limited value. © 2000 Lippincott Williams & Wilkins, Inc.