Neuronal activity in the human brain induces ionic currents across neuronal membranes. These ionic currents generate electric fields which can be measured at the cortical surface in the electrocorticogram (ECoG) and at the scalp in the electroencephalogram (scalp-EEG). Furthermore, each electrical current induces a weak magnetic field according to BiotSavart’s law which can be measured outside the head in the magnetoencephalogram (MEG) . Several important points concerning the biophysical principles underlying the neurogenesis of ECoG, scalp-EEG, and MEG have to be mentioned in the following.
KeywordsStimulus Duration Volume Conductor Cortical Stimulation Synaptic Potential Equivalent Dipole
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