Stimulation of rods can increase cone flicker ERGs in man

Recent psychophysical studies in man and electrophysiological studies in lower vertebrates show that dark adapted, unstimulated rods inhibit cone mediated flicker. This investigation uses comparable psychophysical and ERG procedures in man to demonstrate rod-cone interaction of this type. With either procedure the rod cone interaction cannot be demonstrated with Ganzfeld stimulation. A single small, red, flickering test field, which is a common psychophysical stimulus for testing rod-cone interaction, elicits an immeasurably small cone ERG. But an array of many such targets, flickering synchronously, is an effective psychophysical stimulus and produces an ERG with larger cone than rod components. With such an array, it can be shown that a steady, rod-stimulating background selectively enhances cone ERG components.