THE VEP THRESHOLDS FOR FULL-FIELD STIMULI IN DARK-ADAPTED INFANTS

Dark-adapted adults' electroretinographic b-wave thresholds are simila r to 2 log units below a-wave thresholds and similar to 3 log units ab ove the perceptual threshold, and their perceptual and the visually ev oked cortical potential (VEP) thresholds are similar. Dark-adapted inf ants' scotopic a- and b-wave thresholds for full-field stimuli are bot h about 0.5 log units above those of adults, but their scotopic VEP th resholds for such stimuli have not been studied. We obtained scotopic VEP thresholds for brief, full-field stimuli from dark-adapted, infant s and adults to consider the relationships of the cortical responses t o the responses of more distal structures, namely the rod photorecepto rs (scotopic a-wave) and ON-bipolars (scotopic b-wave). The median VEP threshold of infants is 0.5 log unit above that of adults. Thus, the relationships of a- and b-wave and VEP thresholds in infants are simil ar to those in adults. These results are consistent with rod cell imma turities being the primary determinant of the difference between infan ts' and adults' thresholds.