Combining functional MRI and EEG source imaging

Even though the entire data for multislice imaging in functional magnetic resonance imaging (fMRI) can be acquired in 50-100 ms using echo-planar imaging, the effective temporal resolution for studying brain function is limited to 1-2s due to the relatively slow temporal response of the underlying hemodynamics. The objective of the preliminary study reported here was to combine evoked potential measurements (commonly referred to as EEG) with fMRI of the same subject to improve temporal resolution. EEG and 1.5T fMRI data were acquired from the subjects during checkerboard stimulation. The EEG data were recorded on a standard 10-20 electrode placement system and sources were reconstructed using a 4-sphere model based on the anatomical MRI of the subjects. Simulated annealing based algorithms were developed to estimate single equivalent dipole and multiple dipole parameters for both single time-point and spatio-temporal EEG data. The results from both single and multiple dipole estimations indicate good correlation between the dipole locations and fMRI