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Amithavikram R. Hathibelagal, Beatrix Feigl, Jan Kremers, Andrew J. Zele; Correlated and Uncorrelated Invisible Temporal White Noise Alters Mesopic Rod Signaling. Journal of Vision 2016;16(4):45-46. doi: 10.1167/16.4.48.
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© 2017 Association for Research in Vision and Ophthalmology.
Rods input to all the three retinogeniculate visual pathways under mesopic illumination. The relative rod weights in these pathways vary with the temporal profile of the rod signal. Here, we determined how rod signalling is altered in the presence of correlated (pathway specific) and uncorrelated (rod photoreceptor specific) temporal white noise that does not provide a stimulus for visual perception. Temporal white noise was generated using a 4-primary photostimulator to provide independent control of rod and cone excitations (5 Troland). Psychometric functions (Weibull) were measured with a method of constant stimuli for rod incremental pulses (50 to 250 ms) in the presence (or absence; control) of perceptually invisible (subthreshold) temporal white noise with constant spectral density (0–255 Hz). Three types of correlated noise were generated: Magnocellular (MC) pathway L+M+S noise, Parvocellular (PC) pathway +L-M noise and Koniocellular (KC) pathway S-cone noise. We found that the 3 types of correlated noise differentially affected the rod psychometric functions. Rod threshold elevations were largest with correlated PC pathway noise, intermediate with correlated KC pathway noise and lowest with correlated MC pathway noise. Facilitation was observed in the presence of uncorrelated rod noise. Weibull slopes mostly decreased (16/19 conditions) in the presence of noise. The effect of noise on rod signalling is inversely related to the strength of the rod inputs to the retinogeniculate pathways. We infer that this could be due to a change in observer decision criterion or the relative rod weights in the retinogeniculate pathways.
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