The Effect of OFF-Pathways on the Human ERG Oscillatory Potentials

Abstract

Human OPs are a group of high-frequency, low-amplitude wavelets superimposed on the ascending limb of the b-wave of the ffERG. Therefore, a bandpass filter between 75–300 Hz is required to properly isolate them. Despite extensive research, the cellular origin of OPs remains unresolved, with a potential contribution by the OFF-pathway being debated. The present study investigated the extent to which the OFF-pathway contributes to OPs. FfERG measurements were obtained from 15 participants. The ffERG protocol was adapted from the ISCEV standard protocol, with particular emphasis on systematically increasing the stimulus duration in several steps. In addition to standard extractions, the measurements were analyzed using a complex Morlet wavelet transform and frequency-specific filtering. The results revealed a reduction in energy, particularly in later response components and in higher- frequency ranges of responses to higher luminance levels and longer stimulus durations compared with the standard duration. This effect was most pronounced at the highest luminance. Altogether, it can be concluded that the findings provided evidence for a likely influence of the OFF-pathway on OPs. Since the observed effects were limited to a specific range, a modulatory function of the OFF-pathway can be assumed. Furthermore, the influence of the OFF-pathway showed variability with respect to the applied luminance.