Testing hypotheses about development with electroretinographic and incremental-threshold data.

Electroretinographic (ERG) and incremental-threshold [threshold-versus-intensity (tvi)] data have been used to infer mechanisms of development. For a hypothesis about development to be tested, the hypothesis must be specified in the context of a model of the adult visual system. Here, published ERG and tvi data obtained from infants are analyzed in the context of models with two sites. The first site in each of these models has the properties of the rod receptors. By a combination of hypotheses about development and these models, other hypotheses are considered. Taken together, the ERG and tvi data are consistent with a scheme in which developmental changes during the first 18 weeks occur largely, if not entirely, in the retina. Some of these changes may be receptoral in origin. The need for explicit adult models and explicit developmental hypotheses is emphasized.