Figure 1.

Left: a schematic illustration depicting the sagittal cut of the primary somatosensory cortex. The P20/N20 component of the somatosensory activity occurs in the Brodmann area 3b, which is located in the posterior wall of the central sulcus [24]. Right: the orientation of the primary currents (somatosensory evoked potential (SEP)/somatosensory evoked field (SEF) components) in the cerebral cortex is normal with respect to the surface due to the normal alignment of the pyramidal cells [10].