Correlation between fmri and source reconstructed eeg of steady state visual evoked potentials

Abstract

Electroencephalography (EEG) is a common technique for studying and understandingthe functioning of the brain. In addition, functional Magnetic ResonanceImaging (fMRI), in the recent years has been a very conventional method for neuroimaging.The most important property of the EEG, which makes it superior to otherneuroimaging modalities is its very high temporal resolution. EEG reects functionalactivities in the range of milliseconds. However, due to limited number of electrodemeasurements and some modeling failures, it can provide limited spatial resolution.fMRI provides satisfactory spatial resolution for imaging of these processes but it lacksgood temporal resolution. In this thesis, the steady state human visual evoked potentialsand their corresponding fMRI scans are processed using EEG source reconstructionand fMRI statistical parametric mapping methods. The visual stimulationsare ranging from 2 to 10 Hz. The fMRI voxels which proved signicantly active werecorrelated with their associated EEG neuroelectric power which was determined on thesame geometric head with Low Resolution Electromagnetic Tomography (LORETA).Spatially averaged positive BOLD, post-stimulus undershoot and LORETA amplitudesare determined across the frequencies as well as the spatial correlations between thepositive BOLD and LORETA amplitudes over an activation mask. Finally, the correlationbetween the standardized regression parameter due to the steady state visualeect and the LORETA amplitudes were also computed over the frequencies. The mostconsistent observation for all these analyses is the signicant activation increase at 8Hz together with a strong correlation between the two imaging modalities.Keywords: fMRI, EEG, Source Localization, Statistical Parametric Mapping, GeneralLinear Model, Statistical Inference, T Test, Forward Problem, Inverse Problem,LORETA.