Retinal pathway origins of the pattern electroretinogram (PERG)

Area of Science:

• Neuroscience
• Ophthalmology
• Retinal Physiology

Background:

• The pattern electroretinogram (PERG) is a valuable tool for assessing retinal function.
• Understanding the specific neural pathways contributing to PERG components is crucial for interpreting clinical findings.

Purpose of the Study:

• To elucidate the retinal pathway origins of transient and steady-state PERGs in macaque monkeys.
• To differentiate the contributions of ON and OFF retinal pathways to PERG signals using pharmacologic agents.

Main Methods:

• Recording of transient and steady-state PERGs and electroretinograms (ERGs) in macaque monkeys.
• Intravitreal injections of L-AP4 (to block ON pathway), PDA (to block hyperpolarizing neurons), and TTX (to block spiking activity).
• PERG simulations were created by averaging ON and OFF responses.

Main Results:

• L-AP4 reduced transient PERG amplitudes, while PDA eliminated negative components (N95, N2) and enhanced positive components (P50, P1).
• TTX and experimental glaucoma affected PERG components differently, indicating roles for spiking and non-spiking neurons.
• Steady-state PERGs were eliminated by L-AP4, suggesting a strong ON pathway contribution, whereas PDA enhanced responses.

Conclusions:

• Transient PERGs arise from nearly equal contributions of both ON and OFF retinal pathways.
• The N95 component reflects ganglion cell spiking activity, while P50 involves both spiking and non-spiking neuronal activity.
• Steady-state PERGs are predominantly driven by spike-related activity within the ON pathway.