Origin of the oscillatory potentials in the primate retina.

The current source and sink profiles of the oscillatory potentials (OPs) of the primate (macaque) electroretinogram (ERG) were studied. The intraretinal local ERG (LERG) and the local resistivity were recorded with a bipolar microelectrode in the intact macaque eye in response to a 10 deg and full field stimulus. A statistical method, a principle component analysis, was performed on high pass digitally filtered LERGs to extract and more closely study the oscillatory components of the LERG's at a number of electrode depths in the retina. The OPs were found to represent radial current flow and to have a current distribution different from those of the receptor and b-wave components. They are generated more proximal than the a- and b-waves, most probably by the bipolar cells. However, the interplexiform cell cannot be excluded as a generator. If so, the OPs should represent activity in a feed-back neural pathway in the inner part of the retina, also in the primate. The OPs can be used to monitor the inner neuronal layer but further differentiation in depth regarding consecutive peaks is not possible.