Visual evoked potential (VEP) measured by simultaneous 64-channel EEG and 3T fMRI

WE present the first simultaneous measurements of evoked potentials (EPs) a nd fMRI hemodynamic responses to visual stimulation. Visual evoked potentia ls (VEPs) were recorded both inside and outside the static 3T magnetic fiel d, and during fMRI examination. We designed, constructed, and tested a non- magnetic 64-channel EEG recording cap. By using a large number of EEG chann els it is possible to design a spatial filter capable of removing the artif act noise present when recording EEG/EPs within a strong magnetic field. We show that the designed spatial filter is capable of recovering the ballist ocardiogram-contaminated original EEG signal. Isopotential plots of the ele ctrode array recordings at the peak of the VEP response (similar to 100 ms) correspond well with simultaneous fMRI observed activated areas of primary and secondary visual cortices. NeuroReport 10:1893-1897 (C) 1999 Lippincot t Williams & Wilkins.