A comparison between electric source localisation and fMRI during somatosensory stimulation.

The present study investigates the electric source localisation of somatosensory evoked potentials (SEPs) using high-resolution EEG (61 scalp electrodes) considering the individual brain morphology as obtained from magnetic resonance images (MRI). A comparison with the activation maps in fMRI under the same somatosensory stimulation paradigm was done. The somatosensory evoked potentials (SEPs) to electrical stimulation of the right median nerve were collected from the scalp of 8 healthy right-handed subjects. The source reconstruction for the 20 ms SEP component was performed by using a single moving dipole model as a source model and a spherical three-shell model as a head model. In 6 of the subjects fMRI was performed using the same electric stimulation of the right median nerve. The source location of the 20 ms SEP component was found to be within the postcentral gyrus. The fMRI activation maps were also located in the postcentral gyrus when using the same somatosensory stimulation paradigm. The appropriateness of using high-resolution EEG and fMRI in the functional localisation of the primary somatosensory cortex is discussed.