Ala-Laurila, P. | Search bioRxiv

bioRxiv2022

Human retina trades single-photon detection for high-fidelity contrast encoding

We lack a fundamental understanding of how the spike output of the retina enables human visual perception. Here we show that human vision at its ultimate sensitivity limit depends on the spike output of ON but not OFF parasol (magnocellular) ganglion cells. Surprisingly, nonlinear signal processing in the retinal ON pathway precludes perceptual detection of single photons in darkness, but enables quantal-resolution discrimination of differences in light intensity.

neuroscience↗

bioRxiv2021

Retinal OFF ganglion cells allow detection of quantal shadows at starlight

Perception of light in darkness requires no more than a handful of photons and this remarkable behavioral performance can be directly linked to a particular retinal circuit - the retinal ON pathway. However, the neural limits to shadow detection in very dim light have remained unresolved. Here, we unravel the neural mechanisms that determine the sensitivity of mice to the dimmest light decrements by measuring signals from the most sensitive ON and OFF retinal ganglion cell types and by correlating their signals with visually guided behavior. We show that mice can detect shadows when only a few photon absorptions are missing among thousands of rods. Behavioral detection of "quantal" shadows relies only on the retinal OFF pathway and is limited by noise and losses of single-photon signals in retinal processing. Thus, in the dim-light regime, light increments and decrements are encoded separately via the ON and OFF retinal pathways, respectively.

neuroscience↗