title: Nonlinear blood oxygen level-dependent responses for transient activations and deactivations in V1 - insights into the hemodynamic response function with the balloon model.
abstract: We report studies of the nonlinear nature of blood oxygen level-dependent (BOLD) responses to short transient deactivations in human visual cortex. Both functional magnetic resonance imaging (fMRI) and near-infrared spectroscopy (NIRS) have been used to compare and contrast the hemodynamic response functions (HRFs) associated with transient activation and deactivation in primary visual cortex. We show that signal decreases for short duration deactivations are smaller than corresponding signal increases in activation studies. Moreover, the standard balloon model of BOLD effects may be modified to account for the observed nonlinear nature of deactivations by appropriate changes to simple hemodynamic parameters without recourse to new assumptions about the nature of the coupling between activity and oxygen use.
authors.affiliation: Department of Physics, Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN 37312, USA. in.tang@alumni.vanderbilt.edu
authors.forename: Lin
authors.initials: L
authors.lastname: Tang
authors.forename: Malcolm J
authors.initials: MJ
authors.lastname: Avison
authors.forename: John C
authors.initials: JC
authors.lastname: Gore
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods*; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008955:Models, Cardiovascular; D008959:Models, Neurological; D017711:Nonlinear Dynamics; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption / Q000502:physiology*; D014793:Visual Cortex / Q000502:physiology*; D055815:Young Adult
chemical_list: D010100:Oxygen