title: The importance of distributed sampling in blocked functional magnetic resonance imaging designs.
abstract: In this study we demonstrate the importance of distributed sampling of peristimulus time in blocked design fMRI studies. Distributed sampling ensures all the components of an event-related hemodynamic response are sampled and avoids the bias incurred when stimulus presentation is time-locked to data acquisition. We found that differences in the temporal offset between stimulus presentation and data acquisition had a significant effect on some language-related activations. These effects, induced by simply shifting stimulus presentation by a fraction of the interscan interval, suggest that fixed sampling does indeed bias estimated responses, even in blocked designs.
authors.affiliation: PET Center, Vrije Universiteit Medical Center. De Boelelaan 1117, Amsterdam, The Netherlands.
authors.forename: Dick J
authors.initials: DJ
authors.lastname: Veltman
authors.forename: Andrea
authors.initials: A
authors.lastname: Mechelli
authors.forename: Karl J
authors.initials: KJ
authors.lastname: Friston
authors.forename: Cathy J
authors.initials: CJ
authors.lastname: Price
mesh_terms: D000328:Adult; D001288:Attention / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods*; D002540:Cerebral Cortex / Q000502:physiology*; D004292:Dominance, Cerebral / Q000502:physiology; D005260:Female; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D010100:Oxygen / Q000097:blood; D011932:Reading; D012016:Reference Values
chemical_list: D010100:Oxygen