title: The continuing challenge of understanding and modeling hemodynamic variation in fMRI.
abstract: Interpretation of fMRI data depends on our ability to understand or model the shape of the hemodynamic response (HR) to a neural event. Although the HR has been studied almost since the beginning of fMRI, we are still far from having robust methods to account for the full range of known HR variation in typical fMRI analyses. This paper reviews how the authors and others contributed to our understanding of HR variation. We present an overview of studies that describe HR variation across voxels, healthy volunteers, populations, and dietary or pharmaceutical modulations. We also describe efforts to minimize the effects of HR variation in intrasubject, group, population, and connectivity analyses and the limits of these methods.
authors.affiliation: Section on Functional Imaging Methods, Laboratory of Brain and Cognition, National Institute of Mental Health, 10 Center Dr, Room 1D80, MSC1148, Bethesda, MD 20814, USA. handwerkerd@mail.nih.gov
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Handwerker
authors.forename: Javier
authors.initials: J
authors.lastname: Gonzalez-Castillo
authors.forename: Mark
authors.initials: M
authors.lastname: D'Esposito
authors.forename: Peter A
authors.initials: PA
authors.lastname: Bandettini
mesh_terms: D001921:Brain / Q000098:blood supply* / Q000502:physiology; D001931:Brain Mapping / Q000266:history* / Q000379:methods; D002560:Cerebrovascular Circulation / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology*; D049673:History, 20th Century; D049674:History, 21st Century; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000266:history / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000266:history* / Q000379:methods; D008959:Models, Neurological