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Amithavikram R Hathibelagal, Beatrix K Feigl, Andrew J Zele; Extrinsic noise modifies the post-receptoral pathway rod weights. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5409.
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© ARVO (1962-2015); The Authors (2016-present)
Temporal white noise that selectively stimulates one of the three post-receptoral pathways (correlated noise) or a single type of photoreceptor class (uncorrelated noise) alters mesopic rod sensitivity (masking or facilitation) and increases variability in rod signalling (Hathibelagal, Feigl, Kremers & Zele, JOSA, 2015, 33(3), A93-A103); the mechanism underlying this phenomenon is unknown. We hypothesize that these effects could be due to a change in the observer decision criterion and/or altered rod weights in the post-receptoral pathways.
The rod and three cone photoreceptor excitations were independently controlled using a four-primary photostimulator to generate correlated and uncorrelated temporal white noise (0-255 Hz). Experiment 1 measured receiver operating characteristic (ROC) curves using a method of constant stimuli with rod incremental pulses by varying the stimulus probability (10-90%). The probability scores were converted to Z-scores and plotted in inverse cumulative Gaussian axes. Experiment 2 estimated the rod signal weights by perceptually matching a 20% rod incremental pulse (50-250ms) by altering the L+M (MC pathway), L/[L+M] (PC pathway) and S/[L+M] (KC pathway) cone excitations. The magnitude and ratio of rod weights in the post-receptoral pathways were quantified with noise and compared to a control condition (no noise). The resultant noise and control matches were then compared to determine if there was a perceptual effect of the change in rod weights.
In Experiment 1, the noise and control ROC slopes were parallel; rod noise (slope = 0.68) vs control (slope = 0.67); LMS noise (0.89) vs control (0.94); +L-M noise (0.93) vs control (0.92); S-cone noise (0.62) vs control (0.58). In Experiment 2, the correlated and uncorrelated noise decreased the luminance weights in 91% (40/44) of the test conditions and decreased the chromatic weights in 69.3% (61/88) of the test conditions. The change in rod weights were not accompanied by a perceptual difference in the colour match between the noise and control conditions for any stimulus duration.
Temporal white noise does not alter the observer decision criterion but acts to change the rod weights in the post-receptoral pathways, which may be an intrinsic response to noise to maintain constant visual perception.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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