Left-right asymmetry of visual evoked potentials in a realistic 3-dimensional numerical model of the head

The distribution of electric potentials was studied by using a realistic 3-D numerical model of the head. Computerized Tomography (CT) imaging scans were used to construct the three dimensional model of the head. Several compartments of the head were defined and a different conductivity was assigned for each compartment. The integral conservation equation in biological volume conductor was solved numerically by a finite volume method for the potential distribution created by dipole sources in the occipital region. The influence of several parameters, such as the geometry of the head, the location of the current source, and the presence of damaged tissue, on the left-right asymmetry of the surface Visual Evoked Potentials (VEP) were examined. The numerical model revealed that the major source of scalp potential asymmetry (Right-Left) is due to asymmetric location of the source (a change of 1.30 Arbitrary Units in O₁-O₂ pair of electrodes for falx deviation of 1° between the occiput and the nasion-inion line). It was also found that the left-right asymmetry in the scalp VEP due to changes in the conductivity of the volume conductor (a damaged region) between the source and the electrodes is insignificant (0.001 Arrbitry Units in P₃-P₄ pair of electrodes)