20-Hz flicker stimulus can isolate the cone function in rat retina

Cone electroretinograms (ERGs) are typically isolated in humans by flicker stimuli against rod-desensitizing adapting fields. To investigate the manner in which adapting-field luminance affects the cone ERGs, we recorded ERGs in normal albino Sprague-Dawley rats with flicker stimuli presented against adapting fields that ranged in luminance from -∞ to 1.75 log cd/m². A flicker rate of 20 Hz was used to isolate the cone ERGs under all adaptation conditions. We found the amplitudes of cone ERGs to increase with increasing adapting-field luminance. These response characteristics are similar to human ERGs using 30-Hz flicker stimuli, which suggests that flicker stimuli are a useful technique to isolate the cone function in rats.