scholarly journals The dual rod system of amphibians supports colour discrimination at the absolute visual threshold

2017 ◽  
Vol 372 (1717) ◽  
pp. 20160066 ◽  
Author(s):  
Carola A. M. Yovanovich ◽  
Sanna M. Koskela ◽  
Noora Nevala ◽  
Sergei L. Kondrashev ◽  
Almut Kelber ◽  
...  
Keyword(s):  
Green Light ◽  
Intrinsic Noise ◽  
Colour Discrimination ◽  
Visual Threshold ◽  
Light Levels ◽  
Rod System ◽  
Specific Factors ◽  
The Absolute ◽  
Behavioural Experiments ◽  
Processing Colour

The presence of two spectrally different kinds of rod photoreceptors in amphibians has been hypothesized to enable purely rod-based colour vision at very low light levels. The hypothesis has never been properly tested, so we performed three behavioural experiments at different light intensities with toads ( Bufo ) and frogs ( Rana ) to determine the thresholds for colour discrimination. The thresholds of toads were different in mate choice and prey-catching tasks, suggesting that the differential sensitivities of different spectral cone types as well as task-specific factors set limits for the use of colour in these behavioural contexts. In neither task was there any indication of rod-based colour discrimination. By contrast, frogs performing phototactic jumping were able to distinguish blue from green light down to the absolute visual threshold, where vision relies only on rod signals. The remarkable sensitivity of this mechanism comparing signals from the two spectrally different rod types approaches theoretical limits set by photon fluctuations and intrinsic noise. Together, the results indicate that different pathways are involved in processing colour cues depending on the ecological relevance of this information for each task. This article is part of the themed issue ‘Vision in dim light’.

A Neural Mechanism for Processing Colour Information in Molluscan Extra-Ocular Photoreceptors

1992 ◽  
Vol 168 (1) ◽  
pp. 77-91
Author(s):  
TAKAKO NISHI ◽  
TSUKASA GOTOW
Keyword(s):  
Green Light ◽  
Receptor Potential ◽  
Neural Mechanism ◽  
Colour Discrimination ◽  
Yellow Light ◽  
Marine Mollusc ◽  
Synaptic Potentials ◽  
Reversed Polarity ◽  
Processing Colour ◽  
Inhibitory Synaptic Input

This study was conducted to clarify the electrical and spectral properties of the combined photoresponses of two extra-ocular photoreceptor neurones, A-P-l and Es-1, in the abdominal ganglion of the marine mollusc Onchidium verruculatum. The depolarizing receptor potential or inward receptor current of Es-1 appeared to result from a decrease in K+ conductance, in the same way as in A-P-l. The direct photoresponse of Es-1 had a peak at 580 nm, while A-P-l had its peak at 490nm. Under normal conditions, Es-1 was hyperpolarized by blue-green light (490nm) and was depolarized by yellow light (580nm), indicating that its responses were wavelength-dependent. Slow inhibitory synaptic potentials in Es-1 occurred during a sustained depolarization of A-P-l, suggesting that Es-1 received some inhibitory synaptic input from A-P-l. The amplitude of these slow synaptic hyperpolarizations was dependent on graded changes in the depolarization of A-P-l. However, presynaptic spikes in A-P-l were not followed by discrete synaptic potentials in Es-1. These results suggest that graded photoresponses of A-P-l could produce the slow hyperpolarization of Es-1 and that the photoresponse of A-P-l is thereby transmitted to Es-1 with reversed polarity. The differing responses of Es-1 to light of different wavelengths may have a role in colour discrimination. Note: To whom reprint requests should be addressed.

scholarly journals Thresholds and noise limitations of colour vision in dim light

2017 ◽  
Vol 372 (1717) ◽  
pp. 20160065 ◽  
Author(s):  
Almut Kelber ◽  
Carola Yovanovich ◽  
Peter Olsson
Keyword(s):  
Shot Noise ◽  
Colour Vision ◽  
Absolute Threshold ◽  
Colour Discrimination ◽  
Dark Noise ◽  
Visual Threshold ◽  
Light Intensities ◽  
Purkinje Shift ◽  
Dim Light ◽  
Receptor Noise

Colour discrimination is based on opponent photoreceptor interactions, and limited by receptor noise. In dim light, photon shot noise impairs colour vision, and in vertebrates, the absolute threshold of colour vision is set by dark noise in cones. Nocturnal insects (e.g. moths and nocturnal bees) and vertebrates lacking rods (geckos) have adaptations to reduce receptor noise and use chromatic vision even in very dim light. In contrast, vertebrates with duplex retinae use colour-blind rod vision when noisy cone signals become unreliable, and their transition from cone- to rod-based vision is marked by the Purkinje shift. Rod–cone interactions have not been shown to improve colour vision in dim light, but may contribute to colour vision in mesopic light intensities. Frogs and toads that have two types of rods use opponent signals from these rods to control phototaxis even at their visual threshold. However, for tasks such as prey or mate choice, their colour discrimination abilities fail at brighter light intensities, similar to other vertebrates, probably limited by the dark noise in cones. This article is part of the themed issue 'Vision in dim light’.

Emerging research in plant photosynthesis

2020 ◽  
Vol 4 (2) ◽  
pp. 137-150 ◽  
Author(s):  
Thomas D. Sharkey
Keyword(s):  
Green Light ◽  
Basic Research ◽  
Light Energy ◽  
Good News ◽  
Regulatory Mechanisms ◽  
Large Area ◽  
Protective Mechanisms ◽  
Light Levels ◽  
Plant Photosynthesis ◽  
To Come

Photosynthesis involves capturing light energy and, most often, converting it to chemical energy stored as reduced carbon. It is the source of food, fuel, and fiber and there is a resurgent interest in basic research on photosynthesis. Plants make excellent use of visible light energy; leaves are ideally suited to optimize light use by having a large area per amount of material invested and also having leaf angles to optimize light utilization. It is thought that plants do not use green light but in fact they use green light better than blue light under some conditions. Leaves also have mechanisms to protect against excess light and how these work in a stochastic light environment is currently a very active area of current research. The speed at which photosynthesis can begin when leaves are first exposed to light and the speed of induction of protective mechanisms, as well as the speed at which protective mechanisms dissipate when light levels decline, have recently been explored. Research is also focused on reducing wasteful processes such as photorespiration, when oxygen instead of carbon dioxide is used. Some success has been reported in altering the path of carbon in photorespiration but on closer inspection there appears to be unforeseen effects contributing to the good news. The stoichiometry of interaction of light reactions with carbon metabolism is rigid and the time constants vary tremendously presenting large challenges to regulatory mechanisms. Regulatory mechanisms will be the topic of photosynthesis research for some time to come.

scholarly journals Behavioural and physiological limits to vision in mammals

2017 ◽  
Vol 372 (1717) ◽  
pp. 20160072 ◽  
Author(s):  
Greg D. Field ◽  
Alapakkam P. Sampath
Keyword(s):  
Single Photon ◽  
Signal Transmission ◽  
High Sensitivity ◽  
Human Vision ◽  
Past Century ◽  
Single Photons ◽  
Rod Photoreceptors ◽  
Physiological Limits ◽  
Visual Threshold ◽  
Behavioural Experiments

Human vision is exquisitely sensitive—a dark-adapted observer is capable of reliably detecting the absorption of a few quanta of light. Such sensitivity requires that the sensory receptors of the retina, rod photoreceptors, generate a reliable signal when single photons are absorbed. In addition, the retina must be able to extract this information and relay it to higher visual centres under conditions where very few rods signal single-photon responses while the majority generate only noise. Critical to signal transmission are mechanistic optimizations within rods and their dedicated retinal circuits that enhance the discriminability of single-photon responses by mitigating photoreceptor and synaptic noise. We describe behavioural experiments over the past century that have led to the appreciation of high sensitivity near absolute visual threshold. We further consider mechanisms within rod photoreceptors and dedicated rod circuits that act to extract single-photon responses from cellular noise. We highlight how these studies have shaped our understanding of brain function and point out several unresolved questions in the processing of light near the visual threshold. This article is part of the themed issue ‘Vision in dim light’.

Response of carp (Cyprinus carpio) horizontal cells to heterochromatic flicker photometry

2006 ◽  
Vol 23 (3-4) ◽  
pp. 437-440 ◽  
Author(s):  
MARLISON JOSÉ L. DE AGUIAR ◽  
DORA FIX VENTURA ◽  
MANOEL DA SILVA FILHO ◽  
JOHN MANUEL DE SOUZA ◽  
ROGÉRIO MACIEL ◽  
...  
Keyword(s):  
Horizontal Cell ◽  
Red Light ◽  
Green Light ◽  
Physiological Solution ◽  
Horizontal Cells ◽  
Xenon Lamp ◽  
Constant Amplitude ◽  
Light Levels ◽  
Electrophysiological Recordings ◽  
Heterochromatic Flicker Photometry

The objective of the present work was to determine the interaction of cone inputs in the response of horizontal cells using heterochromatic flicker photometry (HFP). Intracellular electrophysiological recordings were made in horizontal cells of isolated retinae of carp maintained in physiological solution, with the receptor side up. Sharp glass microelectrodes filled with 3 M KCl solution with resistances between 100 and 120 MΩ were used. Stimuli comprised six cycles of two 6-Hz sinusoidal light waves in counterphase adjusted for the same number of quanta: a green light (550 nm) from a monochromator with a Xenon lamp and an LED red light (628 nm). The stimulation program consisted of 10 steps with the 550-nm wave at constant amplitude, while the 628-nm wave varied in increments of 10% up to 100%, followed by another 10 steps with the 628-nm wave at constant amplitude while the 550-nm wave varied in increments of 10% up to 100%. We recorded responses from four different horizontal cell classes: H1 (monophasic, broadband, n = 37), H2 (biphasic, red-green color-opponent, n = 13), and H3 (biphasic, blue-yellow color-opponent, n = 2) cone horizontal cells; and RH (monophasic, broadband, n = 3) rod horizontal cells. H1 and RH horizontal cells showed a similar cancellation point at a heterochromatic mixture consistent with mixed inputs from 630- and 550-nm cones. No cancellation point was found for the H2 cell class. Fish H1 cells add cone inputs and signal “luminance” in light levels appropriate for cone stimulation. The same occurs with RH cells, which also signal “luminance,” but in light levels appropriate for rod work. For both cell classes there is an HFP cancellation point occurring at a combination of 628-nm and 550-nm lights in opposing phase that leads to the cancellation of the cell's response. No cancellation was found for H2 and H3 cells, which are the chromatically opponent horizontal cells in lower vertebrates.

scholarly journals Distinct contribution of cone photoreceptor subtypes to the mammalian biological clock

2021 ◽  
Vol 118 (22) ◽  
pp. e2024500118
Author(s):  
Hester C. van Diepen ◽  
Robin A. Schoonderwoerd ◽  
Ashna Ramkisoensing ◽  
Jan A. M. Janse ◽  
Samer Hattar ◽  
...  
Keyword(s):  
Neuronal Activity ◽  
Uv Light ◽  
Biological Clock ◽  
Green Light ◽  
Sustained Response ◽  
Activity Levels ◽  
Cone Photoreceptors ◽  
Light Levels ◽  
Electrophysiological Recordings

Ambient light detection is important for the synchronization of the circadian clock to the external solar cycle. Light signals are sent to the suprachiasmatic nuclei (SCN), the site of the major circadian pacemaker. It has been assumed that cone photoreceptors contribute minimally to synchronization. Here, however, we find that cone photoreceptors are sufficient for mediating entrainment and transmitting photic information to the SCN, as evaluated in mice that have only cones as functional photoreceptors. Using in vivo electrophysiological recordings in the SCN of freely moving cone-only mice, we observed light responses in SCN neuronal activity in response to 60-s pulses of both ultraviolet (UV) (λmax 365 nm) and green (λmax 505 nm) light. Higher irradiances of UV light led to irradiance-dependent enhancements in SCN neuronal activity, whereas higher irradiances of green light led to a reduction in the sustained response with only the transient response remaining. Responses in SCN neuronal activity decayed with a half-max time of ∼9 min for UV light and less than a minute for green light, indicating differential input between short-wavelength–sensitive and mid-wavelength–sensitive cones for the SCN responsiveness. Furthermore, we show that UV light is more effective for photoentrainment than green light. Based on the lack of a full sustained response in cone-only mice, we confirmed that rapidly alternating light levels, rather than slowly alternating light, caused substantial phase shifts. Together, our data provide strong evidence that cone types contribute to photoentrainment and differentially affect the electrical activity levels of the SCN.

scholarly journals Optimizing the use of a sensor resource for opponent polarization coding

2016 ◽  
Author(s):  
Francisco J. H. Heras ◽  
Simon B Laughlin
Keyword(s):  
Mutual Information ◽  
Signal To Noise Ratio ◽  
Limited Resource ◽  
Signal Amplitude ◽  
Intrinsic Noise ◽  
Polarization Angle ◽  
Photon Noise ◽  
Light Levels ◽  
Skylight Polarization ◽  
Lower Light

Flies use specialized photoreceptors R7 and R8 in the dorsal rim area (DRA) to detect skylight polarization. R7 and R8 form a tiered waveguide (rhabdom) with R7 on top, filtering light delivered to R8. We examine how the division of a given resource, rhabdom length, between R7 and R8 affects their ability to code polarization angle. We model optical absorption to show how the length fractions allotted to R7 and R8 determine the rates at which they transduce photons, and correct these rates for transduction unit saturation. The rates give polarization signal and photon noise in R7, and in R8. Their signals are combined in an opponent unit, intrinsic noise added, and the unit’s output analysed to extract two measures of coding ability, number of discriminable polarization angles and mutual information. A very long R7 maximizes opponent signal amplitude, but codes inefficiently due to photon noise in the very short R8. Discriminability and mutual information are optimized by maximizing signal to noise ratio, SNR. At lower light levels approximately equal lengths of R7 and R8 are optimal because photon noise dominates. At higher light levels intrinsic noise comes to dominate and a shorter R8 is optimum. The optimum R8 length fractions falls to one third. This intensity dependent range of optimal length fractions corresponds to the range observed in different fly species and is not affected by transduction unit saturation. We conclude that a limited resource, rhabdom length, can be divided between two polarization sensors, R7 and R8, to optimize opponent coding. We also find that coding ability increases sub-linearly with total rhabdom length, according to the law of diminishing returns. Consequently the specialized shorter central rhabdom in the DRA codes polarization twice as efficiently with respect to rhabdom length than the longer rhabdom used in the rest of the eye.

scholarly journals The absolute visual threshold recorded from the lateral geniculate body of the cat

1959 ◽  
Vol 146 (1) ◽  
pp. 179-184 ◽  
Author(s):  
F. H. C. Marriott ◽  
Valerie B. Morris ◽  
M. H. Pirenne
Keyword(s):  
Lateral Geniculate Body ◽  
Visual Threshold ◽  
Lateral Geniculate ◽  
The Absolute

scholarly journals Simulating Physiological Potentials of Daylight Variables in Lighting Design

2022 ◽  
Vol 14 (2) ◽  
pp. 881
Author(s):  
Mimi Ravn ◽  
Gabriela Mach ◽  
Ellen Kathrine Hansen ◽  
Georgios Triantafyllidis
Keyword(s):  
Vertical Plane ◽  
Holistic Approach ◽  
Lighting Design ◽  
Time Of Day ◽  
Physiological Effects ◽  
Smart Building ◽  
Light Levels ◽  
Orientation Time ◽  
Specific Factors ◽  
Sky Conditions

A holistic approach to daylight dynamics in our built environment can have beneficial outcomes for both physiological and visual effects on humans. Simulations of how daylight variables affect light levels on the horizontal work plane are compared to their physiological effects, measured as melanopic EDI (Melanopic Equivalent Daylight Illuminance) on a vertical plane. The melanopic EDI levels were calculated in a simulated office space in ALFA software (Adaptive Lighting for Alertness) employing the daylight variables of orientation, time of day, season, sky conditions and spatial orientation. Results were analyzed for how daylight design can contribute to the physiological effects of dynamic light in office buildings. Daylight is shown to be a sufficient light source in the majority of cases to meet the recommended values of EDI and provide the suggested horizontal lx level according to the Danish Standards. A mapping of daylight conditions, focusing on the specific factors presented here, can provide guidelines in the design process and future smart building systems. The complex interrelationship between these parameters is important to acknowledge when working with daylight dynamics as a sustainable element in architecture and lighting design.

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