Contribution from proximal retina to intraretinal pattern ERG: the M-wave.

Intraretinal electroretinographic (ERG) responses were recorded from cat to spatial square wave gratings that were reversed in contrast (pattern ERG, PERG). Maximum 8 Hz PERG amplitudes occurred in proximal retina. Intraretinal ERGs to circular spots (photopic) also were maximal in proximal retina and resembled the M-waves of cold-blooded retinas. The temporal transforms of M-wave responses to 8 Hz flicker (to simulate contrast reversal conditions) imitated the 8 Hz PERG, suggesting that the M-wave may contribute significantly to the PERG.