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Jussi Tiihonen, Amir Tavala, Krishna Dovzhik, Petri Ala-Laurila; Retinal loss sets a fundamental limit to the variance of visual signals originating from single-photon stimulation. Invest. Ophthalmol. Vis. Sci. 2020;61(7):1106.
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The uncertainty arising from Poisson statistics of light has until recently precluded the possibility to stimulate the visual system with precise number of photons. Recent studies utilizing a single-photon gun (SPG) postulate that it is possible to produce sub-Poisson signal statistics in retinal rods1 and in human psychophysics2. However, the key prerequisite for these results has remained untested, namely that the loss of single-photon signals in the retina strictly constrains the extent at which biological signal statistics can deviate from Poisson statistics. Now we test the impact of single-photon loss on the variability of visual signals from rods to human psychophysics at the sensitivity limit of vision.
We stimulated toad (Bufo marinus) retinal rods axially using a state-of-the-art SPG and measured their light-sensitive current using suction pipette technique. We measured the minimum loss of single-photon signals in rods. Finally, we estimated the minimum loss of single-photon signals across the relevant pathway in the primate retina (rod bipolar pathway) to analyze the minimum number of trials required for distinguishing the biological signal distributions originating from a Poisson source or a SPG.
We estimate that the minimum cumulative single-photon loss in rods is 86% (source loss: ~75%, rod loss ~43%), requiring a minimum of ~3 000 trials in optimal conditions for a statistically significant difference between the response distributions arising from a Poisson source or a SPG. The cumulative single-photon loss in human psychophysics experiments even with a lossless SPG was estimated to be ~99.5%, requiring a minimum of > 4 000 000 trials (several months of experiment) and a perfect memory for distinguishability in response distributions between Poisson and SPG stimulation.
We show that due to the loss of single-photon signals it is impossible to distinguish the response distributions originating from Poisson or SPG sources in retinal outputs or at the level of perception on a biologically relevant timescale. Our results require a fundamental re-evaluation of the previous results relying on SPG stimulation and set tight constraints to which extent visual signal statistics can deviate from Poisson statistics at the sensitivity limit.1Phan et al. (2014). Phys. Rev. Lett. 112, 213601.2Tinsley et al. (2016). Nature Communications 7, 12172.
This is a 2020 ARVO Annual Meeting abstract.
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