Abstract
Purpose :
To study ERGs elicited by temporal white noise (TWN) stimuli that excite only the L- or the M-cones or all photoreceptors in concert.
Methods :
ERGs were recorded from the right eyes of five anesthetized macaques (Macaca mulatta ; three males, two females). Stimuli were created with a 4-colour ganzfeld stimulator. The stimuli were luminance (22% contrast), selective L-cone excitation and selective M-cone excitation (both 22% cone contrast). Cone isolating stimuli were generated using triple silent substitution. The stimuli had equal amplitudes at all frequencies between 0 and 512 Hz. Inverse Fourier transform resulted in a TWN stimulus with a Gaussian luminance or cone excitation distribution. All ERG measurements were performed twice to study reproducibility and correlations.
Results :
The repeated measurements showed that the measured ERGs were reproducible. The responses to identical stimuli measured in different animals were correlated but less strongly as the responses to the same stimuli in the same animals. A cross-correlation between ERG responses and stimuli resulted in impulse response functions (IRFs) for luminance stimuli that were similar to flash ERGs in having an a-wave-like negativity and a b-wave-like positivity, but lacked oscillatory potentials and showed a late (after 40 ms) positive wave. L-cone driven IRFs were similar to luminance IRFs albeit smaller. The a- and b-wave-like components were absent in the M-cone driven IRFs. The M-cone driven late positivity was of similar amplitude as those obtained for L-cone isolating stimuli.
Conclusions :
ERGs elicited with temporal white noise are reproducible. The a-like and b-like waves of the luminance IRF are L-cone dominated as previous seen for ERG responses in humans and macaques to sine wave, square wave and sawtooth stimuli. A late positive wave, present in luminance, L- and M-cone IRFs but not visible in conventional flash ERGs may provide a new measure of retinal function.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.