The relation between the after-negative potential of the pattern electroretinogram and the visually evoked cortical potential.

The relationship between the after-negative potential of the pattern electroretinogram (PERG) and the visually evoked cortical potential (VECP) was studied. The PERG was recorded through the use of Toray's high water content, soft contact lens electrode. The PERG consisted of an initial positive potential, a subsequent negative potential and then a slow positive potential. To reduce or avoid contamination of the VECP on the PERG, the most important factor was found to be the reference electrode position; special attention was paid in cases where the amplitude of the VECP was large. In the steady-state condition, the PERG was thought to be modulated by the VECP when the ear lobe was used as the reference electrode position; when the temple was used as the reference electrode position, the amplitude of the PERG was thought to represent that of the after-negative potential.