Rod and cone independence in the electroretinogram of the dark-adapted monkey's perifovea.

1. Rod and cone interaction has been studied in the vitreal and intraretinal e.r.g. in the perifovea of the dark-adapted Rhesus monkey retina.2. Rod and cone responses can be completely isolated in the e.r.g. using dim, monochromatic stimuli. The threshold cone response begins at about 50 msec whereas that of the rods begins at 150 msec. There is no detectable interaction between these two responses.3. By comparing the e.r.g. with ganglion cell responses, it is concluded that the time delays and interactions of rod and cone signals arriving at the ganglion cell layer are determined respectively before and after the origin of the b-wave.