If the rate of cone pigment regeneration is decreased, the ERP amplitude should decrease to a lower level during light adaptation. This decrease in the rate of cone pigment regeneration can be accomplished by waiting about 1 hr before dissecting the retina from the whole excised eye (ie by “ageing” the retina). Figure 2 shows ERP amplitudes measured during light and dark adaptation of “aged” and “fresh” retinas. The decreased cone pigment regeneration in the aged retina is indicated by the slowed rate of ERP recovery during dark adaptation, and by the low ERP amplitudes at the end of light adaptation. After the lo-mm bleaching exposure, the relative pigment concentration in the aged retina has dropped