Ontogenesis of the electroretinogram in a precocial mammal, the guinea pig ( Cavia porcellus)

1. 1. Ontogenesis of the electroretinogram, the mass electrical response of the retina to flash light stimuli, was studied in the guinea pig ( Cavia porcellus), a precocial species with visual function at birth. 2. 2. a-Wave components, b-wave, oscillatory potentials, slow PIII, and c-wave responses to flash stimuli developed between 55 and 64 days of gestation (full term is 68–69 days). 3. 3. a-Waves attributable to photoreceptor functions were fully mature at 60 days. 4. 4. ERG development lagged behind the reported critical milestones in retinal development; its prenatal onset indicates that no history of light entrainment is required for initiation of a mature ERG response.