Distinction between a Proximal Negative Response and the Local b Wave in the Retina

Abstract

WHEN light is flashed on the retina, a spatial and temporal pattern of neural activity is produced among several types of retinal cells. The resulting pattern of extracellular voltage can be recorded by placing a microelectrode at various depths within the retina. Recently, most of the graded slow potentials recorded in this way have been identified with components of the intraretinal electroretinogram^1–3. In this communication, I conclude that there is another major type of local extracellular slow potential in the frog retina. This potential, referred to here as the proximal negative response (PNR), is most clearly evident in the proximal (anterior) part of the retina^4,5. In the past, it has been suggested that the PNR and the electroretinogram (ERG) are fundamentally different in nature^4–6. It has never been clearly shown, however, that the PNR can be distinguished from the local, negative intraretinal b wave of the ERG. An alternative hypothesis^3,7 that the PNR may simply be the local b wave therefore seems tenable and apparently prevails at present.