Melanopsin-mediated image statistics from natural and human-made environments.

Melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs) play a critical role in regulating physiological and behavioral responses to light. However, little is known about how melanopsin and ipRGC signals are shaped by the statistical properties of real-world environments. Here, we analyzed the statistics of melanopsin, ipRGC codification of extrinsic and intrinsic photoresponses, and luminance using hyperspectral images of natural and human-made scenes under daylight illumination. The statistics were obtained by modeling human retinal receptive fields from current knowledge about ipRGC anatomy and physiology. Our findings reveal that human-made environments exhibit significantly higher melanopsin, luminance, and ipRGC excitations compared to natural environments. This difference is linked to higher reflectance values in human-made environments. In natural scenes, luminance contrasts were higher than melanopsin and ipRGC contrasts across most of the range. Melanopsin contrast was largely independent of excitation and was significantly reduced for larger receptive fields. Differences between ipRGC codification models suggest an interaction between input weighting and environmental structure. These results indicate that modifications of natural regularities by human-made environments could affect ipRGC-driven physiology in everyday life and may deviate from the evolutionary constraints that shaped ipRGC function.