The origins of luminance and pattern responses of the pattern electroretinogram

A luminance response is spatially insensitive and dependent upon temporal contrast. The contribution of luminance to the pattern onset electroretinogram (PERG) can be estimated from the temporal contrast of a pattern's illuminance profile on the retina. A profile can be computed for different spatial frequencies by resynthesising the Fourier transform of the pattern after it has been filtered by the eye's MTF. A pure luminance response does not fully account for the amplitude of the PERG. The residual response is called "pattern specific". After the effects of spatial contrast degradation have been corrected for the response is spatially bandpass tuned with a peak that changes with eccentricity. An optimum foveal stimulus is estimated to be 3.5' arc. The pattern specific response component shows a correlation with inner nuclear and ganglion cell volumes. When the relationship of the luminance ERG with temporal contrast was explored empirically it was found to behave in good approximation to the theoretical predictions.