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

Area of Science:

• Neuroscience
• Ophthalmology
• Physiology

Background:

• Local electroretinograms (LERGs) provide insights into retinal function.
• Understanding retinal current flow is crucial for diagnosing visual impairments.

Purpose of the Study:

• To localize current sources and sinks for different LERG components in the macaque retina.
• To investigate the distribution of retinal currents as a function of depth.
• To compare primate retinal current patterns with those of lower species.

Main Methods:

• Recording local electroretinograms (LERGs) using microelectrodes at various retinal depths in macaque monkeys.
• Measuring retinal resistivity with a bipolar microelectrode and current pulse.
• Calculating local retinal currents from evoked potentials and resistivity data.

Main Results:

• Localized current sources and sinks for three LERG components: receptor, b-wave, and d.c.-component.
• Receptor component: source in outer segments (90% depth), sink in ONL (70% depth).
• B-wave and d.c.-component: source around 40% depth, sink around 70% depth.
• Primate b-wave current distribution differs from lower species, lacking a proximal layer current source.

Conclusions:

• The study successfully mapped retinal current flow in primates.
• Identified specific depths for current sources and sinks related to LERG components.
• Highlighted species-specific differences in retinal current distribution, particularly for the b-wave.