Simultaneous EEG-fMRI has been applied across many functional brain studies to observe the spatiotemporal patterns of cortical activity that support complex cognitive tasks. Emotion regulation becomes a major topic of interest among these studies, with a particular focus of the late positive potential (LPP), which appears over parietal areas during emotion processing. While prefrontal areas have been linked to the LPP, the manner of their involvement remains poorly understood. In this study, EEG-informed fMRI was applied to investigate the cortical areas that modulate the frontal LPP during emotion regulation. Simultaneous EEG and fMRI data were collected during reappraisal-based emotion regulation, with EEG data analyzed from 400-600ms after task onset. Group Independent Component Analysis (ICA) was applied to denoise the EEG signal and extract common features across trials for all subjects and conditions. Extracted features were then used as regressors in general linear model (GLM)-based fMRI analysis. Results indicate that the septum pellucidum, right insula and right subcallosal gyrus are involved in the modulation of the LPP amplitude in prefrontal regions, as it is seen during reappraisal. Results align with previous emotion reappraisal studies and provide evidence for the use of IC-based EEG-informed fMRI in the study of emotional regulation.