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Alódia Brasil, Tina I Tsai, Givago S Souza, Anderson Manoel Herculano, Dora Fix Ventura, Luiz Carlos L Silveira, Jan J Kremers; The light adaptation phenomenon in human: receptoral and post-receptoral involvement. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3596. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
The amplitudes of full-field flash and flicker electroretinograms (ERG) were found to increase over several minutes during light adaptation (LA) after an extended period in the dark. The aim of this study was to elucidate the involvement of the M- and L-cone photoreceptor streams and their respective post-receptoral pathways during LA using the flicker ERG.
Six healthy subjects (2 male and 4 female, 26-35 years old) with normal trichromatic color vision participated in the study. Four ERG protocols were presented to isolate individually, contributions of: L-cone-driven, M-cone-driven, luminance-driven (LUM), and chromaticity-driven (CHROM) channels at 12 and 36 Hz. All subjects underwent 30 min of dark adaptation before each protocol. Then the adapting light (284 cd/m2) was switched on. Sinusoidal flicker modulation around the adapting field was presented every 2 min from time 0 to time 16 min after light onset. Amplitudes and phases of the fundamental component were obtained from Fourier analysis of all responses. LA-response profiles were fit with an inverse exponential function for each subject to obtain estimates of the semi-saturation time constant (τ) and total amplitude and phase change (Δ).
Most amplitudes and phases changed during LA (except for CHROM 36 Hz amplitude, phase, and CHROM 12 Hz phase). Specifically, they increased as a function of LA (positive Δ). Only with the LUM 12 Hz condition was a negative Δ found. Estimates of τ could be grouped into two categories: one that exhibited shorter τ of approx. 2 min on average (L-cone, M-cone, CHROM 12 Hz, amplitude range 1-4 min, phase 1-2 min), and the other that had a longer τ of 4 min (L-cone, M-cone, LUM 36 Hz, amplitude 3-5 min, phase 2-4). For 12 Hz data, amplitudes and phases exhibited similar time constants for the different isolating conditions. L- and M-cone behaviors with increasing LA time had similar τ at 12 Hz. This was also the case at 36 Hz.
That L-cone and M-cone-driven responses exhibit similar behaviors during LA suggests that the LA-induced changes are likely a post-receptoral phenomenon. LA processes driven by activity in the magnocellular-based luminance (reflected by LUM, L- and M-cone at 36 Hz) and parvocellular-based chromaticity channels (CHROM, L- and M-cone at 12 Hz) show distinct response dynamics (τ of 4 and 2 min, respectively).
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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