The Physical Mechanism for Retinal Discrete Dark Noise: Thermal Activation or Cellular Ultraweak Photon Emission?

Abstract

For several decades the physical mechanism underlying discrete dark noise of photoreceptors in the eye has remained highly controversial and poorly understood. It is known that the Arrhenius equation, which is based on the Boltzmann distribution for thermal activation, can model only a part (e.g. half of the activation energy) of the retinal dark noise experimentally observed for vertebrate rod and cone pigments. Using the Hinshelwood distribution instead of the Boltzmann distribution in the Arrhenius equation has been proposed as a solution to the problem. Here, we show that the using the Hinshelwood distribution does not solve the problem completely. As the discrete components of noise are indistinguishable in shape and duration from those produced by real photon induced photo-isomerization, the retinal discrete dark noise is most likely due to ‘internal photons’ inside cells and not due to thermal activation of visual pigments. Indeed, all living cells exhibit spontaneous ultraweak photon emission (UPE), mainly in the optical wavelength range, i.e., 350–700 nm. We show here that the retinal discrete dark noise has a similar rate as UPE and therefore dark noise is most likely due to spontaneous cellular UPE and not due to thermal activation.

A comprehensive data-driven model of cat primary visual cortex

“…The model does not include any external sources of variability, with the exception of white noise current injection into LGN cells in order to induce their spontaneous firing at about 10 Hz, in line with recordings from visual thalamus (Ghose and Freeman 1992). This noise represents the combined effect of the dark discharge (Cavaggioni 1968) in retina due to photonic noise or intrinsic properties of retinal ganglion cells (Levine 1991;Field and Rieke 2002;Croner et al 1993;Salari et al 2016), and the intrinsic mechanisms generating ongoing activity in thalamus (Rogala et al 2013). Consequently, since the thalamic inputs to Layer 4 neurons form only a small fraction of the modeled cortical synapses (in line with anatomy), the spontaneous activity (and variability in general) in the model is largely due to the internal dynamics of the model.…”

Mechanisms of phosphenes in irradiated patients

“…Spontaneous and induced ultraweak bioluminescent photons may also explain the occurrence of phosphenes independent of the Cherenkov radiation [ 54 , 70 ]. Ultraweak bioluminescent photons are particles permanently present at a low concentration within the eye and brain [ 70 , 71 ].…”

“…Spontaneous and induced ultraweak bioluminescent photons may also explain the occurrence of phosphenes independent of the Cherenkov radiation [ 54 , 70 ]. Ultraweak bioluminescent photons are particles permanently present at a low concentration within the eye and brain [ 70 , 71 ]. They are generated by cells in physiological conditions when these emit free radicals essentially derived from the mitochondrial respiration chain and lipid peroxidation metabolism [ 72 , 73 ].…”

Possible existence of optical communication channels in the brain

“…They are produced mostly by electronically excited molecular species in a variety of oxidative metabolic processes78 in cells. They may play a role in cell to cell communication79, and have been observed in many organisms, including humans, and in different parts of the body, including the brain101112131415. Photons in the brain could serve as ideal candidates for information transfer.…”