A nonlinear BOLD model accounting for refractory effect by applying the longitudinal relaxation in NMR to the linear BOLD model.
A mathematical model to regress the nonlinear blood oxygen level-dependent (BOLD) fMRI signal has been developed by incorporating the refractory effect into the linear BOLD model of the biphasic gamma variate function. The refractory effect was modeled as a relaxation of two separate BOLD capacities corresponding to the biphasic components of the BOLD signal in analogy with longitudinal relaxation of magnetization in NMR. When tested with the published fMRI data of finger tapping, the nonlinear BOLD model with the refractory effect reproduced the nonlinear BOLD effects such as reduced poststimulus undershoot and saddle pattern in a prolonged stimulation as well as the reduced BOLD signal for repetitive stimulation.
Brain Imaging Research Center, University of Pittsburgh, Pittsburgh, PA 15203, USA. kjj1@pitt.edu
Kwan-Jin
KJ
Jung
D000465:Algorithms; D001931:Brain Mapping / Q000379:methods; D003198:Computer Simulation; D019054:Evoked Potentials, Motor / Q000502:physiology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008959:Models, Neurological; D009044:Motor Cortex / Q000502:physiology*; D009068:Movement / Q000502:physiology; D017711:Nonlinear Dynamics; D010101:Oxygen Consumption / Q000502:physiology*; D012032:Refractory Period, Electrophysiological / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity