FIGURE 2.

Three current sources (e.g., synaptic ion channels) located in upper cortical layers of frontal, midline and occipital areas are shown, together with the charge paths they would produce (dotted lines with small arrows). Synaptic currents are usually carried by positive charges (Na⁺ and Ca⁺⁺) that enter cells across dendritic membranes, so current lines show negative charge movement. These charge paths flow bidirectionally to produce fields above the cortex; these are what we measure with EEG surface electrodes. There are also charge paths directed inward, toward the thalamus and brainstem regions. Inward directed charge pathways would extend further because they are propagating through an electrolytic media that is not impeded by the dura and skull. I propose that these current paths would be concentrated toward the center of brains and generate much stronger EMFs compared to outward directed fields. Brain image modified from ProProfs.com.