Electroretinographic responses to alternating gratings in the cat.

Electroretinographic (ERG) responses to alternating sinusoidal gratings were investigated in the anaesthetized cat. The alternating grating ERG, but not the flash ERG, is reduced in amplitude during electrical stimulation of the optic nerve. Temporary retinal ischaemia caused either by clamping of the retinal artery or by increased intraocular pressure differentially affects the ERG responses to gratings or flashes. It has also been confirmed that following retrograde degeneration of ganglion cells caused by unilateral section of the optic nerve the alternating grating ERG disappears while the ERG in response to flashes is unaffected. All these findings indicate that the various electrical retinal sources contribute in a different way to the pattern ERG and flash ERG and suggest that the main source of the pattern ERG is at the ganglion cell level.