A simultaneous EEG and high temporal resolution fMRI study of trial-by-trial fluctuations in visual evoked potentials

Introduction Simultaneous electroencephalography and functional MRI (EEG-fMRI) take advantage of the high temporal resolution of EEG to detect neuronal events of interest, while fMRI can localize, with a high spatial resolution, the hemodynamic response function (HRF) associated with these events. However, the poor temporal resolution of standard fMRI experiments, of the order of seconds, prevents an accurate estimation of the HRF shape at the single-trial level. While the HRF is known to be temporally sluggish, a high temporal resolution may still detect subtle spatial variations related to distinct events visible on EEG. Recently, the development of MR-encephalography (MREG) has allowed whole-brain fMRI with a high temporal resolution of the order of 100 ms [1-3]. This study uses this new technique to investigate trial-bytrial fluctuations related to visual evoked potentials (VEP) recorded with simultaneous EEG-fMRI.