Origin of the electroretinogram in the intact macaque eye--II. Current source-density analysis.

Local electroretinograms (LERGs), evoked by 400 msec flashes of white light, were recorded as a function of retinal depth with a microelectrode in the intact eye of a macaque monkey. Retinal resistivity was measured as the potential difference between the tips of a bipolar microelectrode, resulting from a 300 msec current pulse which was passed through the retina. From the light evoked potentials and the resistivity the local currents in the retina were calculated. Current sources and sinks were localised for three LERG components. The receptor component had a current source in the outer segments (90% depth) and a sink in the ONL (70% depth). Both the b-wave and the d.c.-component had a source around 40% depth and a sink around 70% depth. The distribution of b-wave sources and sinks in primate seems to deviate from that in lower species, since no large current source is found in the most proximal layers.