Comparison of Hemodynamic Response Models in a Combined EEG-fMRI Study of an Epileptic Patient

Independent component analysis (ICA) and statistical parametric mapping (SPM) are two commonly used methods of analyzing fMRI measurements taken from a patient´s brain. Typically, these methods are applied separately to the measurements to produce brain maps indicating where the patient´s brain was active while he or she performed a task or experienced a stimulus. ICA can also be used to develop a hemodynamic response model that can be used as a regressor in SPM of fMRI measurements, a statistical analysis procedure that uses the general linear model (GLM). This may lead to a more accurate method of localizing patient brain activity because the hemodynamic response model is tailored to the patient´s own measurements. In this study, BOLD fMRI data and EEG data were acquired from a continuous EEG-fMRI study done on a patient suffering from refractory right temporal lobe epilepsy. Spatial ICA was performed on the subject´s BOLD fMRI measurements. One hemodynamic response model signal derived from the spatial ICA (sICA) results was generated to use as a regressor in SPM of the subject data. SPM-generated brain maps of the subject data using the canonical hemodynamic response model and the sICA-derived model were compared.