Scalp potentials and magnetic fields of a fully and partially activated central sulcus
Introduction
Due to some disease, such as, stroke or epilepsy, a portion of the cortex could become electrically inactive. This could change the scalp potentials and magnetic field profiles and, hence, could be useful as a diagnostic tool. For this purpose, we modeled the electrical activity of a partially and fully activated central sulcus. We used a finite element model of an adult male subject's head to simulated scalp EEGs and MEGs.
Section snippets
Methods
The scalp potentials and magnetic fields of a part of the central sulcus were simulated with a FEM model of the head constructed from the segmented magnetic resonance (MR) images of an adult male subject. The part of the central sulcus studied extended from 2 to 5 cm from the right side of the midline of the brain. Refer to Fig. 1. The electrical activity was modeled with distributed current dipolar sources (0.1 mA meter) oriented perpendicular to the curved cortical surface. Three
Results
The scalp EEG and MEG of the total sulcus are given in Fig. 2. The electrical and magnetic activity was confined to a portion of the central sulcus on the right side of the brain. The EEG contours are in μV and the MEG contours are in pico Teslas (pT). The positive EEG contours are confined to the right side of the plot and the maximum positive value is almost twice the negative value. The maximum peak value is 6.0 mV and the minimum peak value is 3.8 mV. The activity was confined to the right
Conclusion
The spatial patterns of the scalp potential contours were significantly different for the partial versus full activation. The maximal magnitudes were in relation with the amount of active tissue modeled. Each partial activation gave a uniquely different configuration of peak MEG and EEG locations that could have diagnostic utility. The spatial shifts in the peaks were more pronounced for the MEG compared with the EEG. The EEG and MEG field patterns are not orthogonal to each other as one would
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