The spectral beam attenuation coefficient is an important optical property of natural water used to quantify light propagation and visibility in the aquatic media, and to study the concentration of the water constituents. Although beam attenuation in the ultraviolet spectral range may be particularly informative, to date, no transmissometer capable of measuring the beam attenuation in the ultraviolet is commercially available. The portable hyperspectral beam transmissometer developed in our lab is capable of measuring across a broad spectral range (300–750 nm) at 2 nm spectral resolution. The transmissometer exhibits a small acceptance angle (0.55 to 0.59° across the spectrum), a well collimated spectral light beam, and precision of ±0.012 m −1 . The attenuation of diverse water samples measured with our transmissometer was found to be significantly similar to that measured with a commercially available transmissometer. Moreover, the attenuation of filtered samples, measured with our transmissometer, was significantly similar to their absorption, measured with a bench‐top spectrometer. Testing the transmissometer in the field, the transmission of water samples collected in Lake Malawi, Africa, was measured on site. The magnitude and spectral shape of attenuation were in general agreement with previous reports. All assessment stages confirm the performance, accuracy, and applicability of our transmissometer. The extended spectral range and high spectral resolution of our portable transmissometer make it an excellent tool for studying the characteristics and distribution of dissolved and particulate matter in aquatic media and exploring the constraints imposed on the visibility and visual communication of aquatic organisms known to have ultraviolet photosensitivity.
Summary Signal reception and production form the basis of animal visual communication, and are largely constrained by environmental light. However, the role of environmental light in producing variation in either signal reception or production has not been fully investigated. To chart the effect of environmental light on visual sensitivity and body colouration throughout ontogeny, we measured spectral sensitivity, lens transmission, and body pattern reflectance from juvenile and adult Nile tilapia held under two environmental light treatments. Spectral sensitivity in juveniles reared under a broad-spectrum light treatment and a red-shifted light treatment differed mostly at short wavelengths, where the irradiance of the two light treatments differed the most. In contrast, adults held under the same two light treatments did not differ in spectral sensitivity. Lens transmission in both juveniles and adults did not differ significantly between environmental light treatments, indicating that differences in spectral sensitivity of juveniles originated in the retina. Juveniles and adults held under the two environmental light treatments differed in spectral reflectance, and adults transferred to a third, white light treatment differed in spectral reflectance from their counterparts held under the two original treatments. These results demonstrate that environmental light plays a crucial role in shaping signal reception in juveniles and signal production throughout ontogeny, reinforcing the notion that environmental light has the capacity to influence animal communication, and suggesting that the characteristics of environmental light should be considered in models of ecological speciation.
The underwater light field is an ever-changing environment. Surface waves induce variability in the radiance and the light's polarization. We examined the dependence of the polarization fluctuations associated with diffuse light (not including contribution from direct skylight) on the viewing zenith angle (30 degrees, 70 degrees, and 90 degrees), solar zenith angle (23 degrees -72 degrees), depth of 0.5-3 m, and light wavelength (380-650 nm) while observing within the azimuthal plane in the wind-wave direction. Polarization and radiance fluctuated with time. Light variability (presented by the coefficient of variation calculated over a series of fluctuations in the radiance and percent polarization, and by the standard deviation calculated over a series of fluctuations in the e-vector orientation) was highest at a viewing zenith angle of 70 degrees , depended positively on the solar zenith angle, and decreased with depth at viewing zenith angles of 30 degrees and 70 degrees . Additionally, the variability of the percent polarization was significantly higher than that of the radiance. The temporal light fluctuations offer possibilities, such as enhancing the detection of transparent and reflecting objects; however, they set constraints on the optimal underwater polarization vision by both animals and by the use of instruments.
Abstract While light can affect emotional and cognitive processes of the medial prefrontal cortex (mPFC), no light-encoding was hitherto identified in this region. Here, extracellular recordings in awake mice revealed that over half of studied mPFC neurons showed photosensitivity, that was diminished by inhibition of intrinsically photosensitive retinal ganglion cells (ipRGCs), or of the upstream thalamic perihabenular nucleus (PHb). In 15% of mPFC photosensitive neurons, firing rate changed monotonically along light-intensity steps and gradients. These light-intensity-encoding neurons comprised four types, two enhancing and two suppressing their firing rate with increased light intensity. Similar types were identified in the PHb, where they exhibited shorter latency and increased sensitivity. Light suppressed prelimbic activity but boosted infralimbic activity, mirroring the regions’ contrasting roles in fear-conditioning, drug-seeking, and anxiety. We posit that prefrontal photosensitivity represents a substrate of light-susceptible, mPFC-mediated functions, which could be ultimately studied as a therapeutical target in psychiatric and addiction disorders.
Polarization sensitivity (PS) in vertebrate vision is controversial, perhaps because its underlying mechanism has remained obscure. An issue that might have added to the controversy is that rainbow trout ( Oncorhynchus mykiss ), which have served as the primary model system for polarization-based orientation, lose their ability to orient relative to celestial polarized-light patterns when parr (fry) transform into migratory smolts (juveniles), which would benefit most from polarization-based orientation. Here we addressed two key questions: (1) what is the mechanism underling PS?, and (2) how can the paradoxical loss of PS in trout smolts be reconciled? We assessed PS from optic nerve recordings in parr and smolts and found that the retinal region with enhanced PS shifted from the ventral retina in parr to the dorsal retina in smolts. This adaptation may allow fish to use the most reliable polarization field encountered at each life stage, the celestial polarization field in the shallow-swimming parr and the depth-insensitive underwater polarization field in the deep-swimming smolts. In addition, we assessed spectral sensitivity across the retina and during ontogeny and fit a cascade retinal model to PS data. We found that differential contribution of two cone detectors with orthogonal PS could drive the variation in PS and that feedback from horizontal cells to cones could explain the differential amplification of PS. This elegant arrangement, in which weak PS of cones is amplified and tuned by retinal networks, allows for PS without interfering with sampling of other visual information and illustrates how sensory systems may simultaneously process disparate aspects of physical environments.
(Neuron 109, 2928–2942.e1–e8; September 15, 2021)In the originally published version of this article, there were errors in equations used to determine the length constant (Figures 2D–2F). Although the parameters ri=Ri/πa2 and rm=Rm/2πashould have been used (Hodgkin and Rushton, 1946, Proc. R. Soc. B.), ri=Ri/πa2 and rm=Rm/2πa were used instead. These errors were introduced because an online Brain Science Dictionary that we relied on (https://dx.doi.org/10.14931/bsd.7666) had these errors in their equations. The author of the Brain Science Dictionary has agreed on these errors in response to our inquiry and corrected these on 3 September 2021 (original article with errors: https://bsd.neuroinf.jp/w/index.php?title=%E3%82%B1%E3%83%BC%E3%83%96%E3%83%AB%E7%90%86%E8%AB%96&direction=prev&oldid=46764). These errors caused incorrect values in Figures 2D–2F and suboptimal discussion in the originally published version of the article.The errors do not affect the conclusions of the paper.We apologize for this error. Figures 2D–2F and the related text, as well as the model parameters in STAR Methods, have been modified in the online version of the article.Editorial noteThis correction outlines an error in an underlying formula used to calculate lengths in a passive cable model. This model was added to the paper at the request of reviewers and unfortunately was not checked carefully in re-review. The corrected model is now accurately built but no longer fits entirely with the authors’ initial hypothesis as to how individual branches of bipolar cells can be tuned independently. Thus, the biophysical mechanisms that shape the output of individual bipolar cell axonal branches remain to be fully elucidated. However, the current correction has no bearing on the main conclusion of the paper, which is based on iGluSnFR imaging.Figure 2Passive cable model to simulate electrical spreads of activities along bipolar cell axon terminal branches (original)View Large Image Figure ViewerDownload Hi-res image Download (PPT) (Neuron 109, 2928–2942.e1–e8; September 15, 2021) In the originally published version of this article, there were errors in equations used to determine the length constant (Figures 2D–2F). Although the parameters ri=Ri/πa2 and rm=Rm/2πashould have been used (Hodgkin and Rushton, 1946, Proc. R. Soc. B.), ri=Ri/πa2 and rm=Rm/2πa were used instead. These errors were introduced because an online Brain Science Dictionary that we relied on (https://dx.doi.org/10.14931/bsd.7666) had these errors in their equations. The author of the Brain Science Dictionary has agreed on these errors in response to our inquiry and corrected these on 3 September 2021 (original article with errors: https://bsd.neuroinf.jp/w/index.php?title=%E3%82%B1%E3%83%BC%E3%83%96%E3%83%AB%E7%90%86%E8%AB%96&direction=prev&oldid=46764). These errors caused incorrect values in Figures 2D–2F and suboptimal discussion in the originally published version of the article. The errors do not affect the conclusions of the paper. We apologize for this error. Figures 2D–2F and the related text, as well as the model parameters in STAR Methods, have been modified in the online version of the article. Editorial note This correction outlines an error in an underlying formula used to calculate lengths in a passive cable model. This model was added to the paper at the request of reviewers and unfortunately was not checked carefully in re-review. The corrected model is now accurately built but no longer fits entirely with the authors’ initial hypothesis as to how individual branches of bipolar cells can be tuned independently. Thus, the biophysical mechanisms that shape the output of individual bipolar cell axonal branches remain to be fully elucidated. However, the current correction has no bearing on the main conclusion of the paper, which is based on iGluSnFR imaging. Direction selectivity in retinal bipolar cell axon terminalsMatsumoto et al.NeuronAugust 13, 2021In BriefMatsumoto et al. uncover that cardinal direction selectivity emerges in retinal bipolar cell axon terminals. The selectivity is established de novo at the terminals by starburst amacrine cells, mediated by both cholinergic transmission and wide-field amacrine cells. The bipolar cells transmit tuned glutamate inputs to directional preference-matched ganglion cells. Full-Text PDF Open Access
Two competing theories have been advanced to explain the evolution of multiple cone classes in vertebrate eyes. These two theories have important, but different, implications for our understanding of the design and tuning of vertebrate visual systems. The 'contrast theory' proposes that multiple cone classes evolved in shallow-water fish to maximize the visual contrast of objects against diverse backgrounds. The competing 'flicker theory' states that multiple cone classes evolved to eliminate the light flicker inherent in shallow-water environments through antagonistic neural interactions, thereby enhancing object detection. However, the selective pressures that have driven the evolution of multiple cone classes remain largely obscure. We show that two critical assumptions of the flicker theory are violated. We found that the amplitude and temporal frequency of flicker vary over the visible spectrum, precluding its cancellation by simple antagonistic interactions between the output signals of cones. Moreover, we found that the temporal frequency of flicker matches the frequency where sensitivity is maximal in a wide range of fish taxa, suggesting that the flicker may actually enhance the detection of objects. Finally, using modeling of the chromatic contrast between fish pattern and background under flickering illumination, we found that the spectral sensitivity of cones in a cichlid focal species is optimally tuned to maximize the visual contrast between fish pattern and background, instead of to produce a flicker-free visual signal. The violation of its two critical assumptions substantially undermines support for the flicker theory as originally formulated. While this alone does not support the contrast theory, comparison of the contrast and flicker theories revealed that the visual system of our focal species was tuned as predicted by the contrast theory rather than by the flicker theory (or by some combination of the two). Thus, these findings challenge key assumptions of the flicker theory, leaving the contrast theory as the most parsimonious and tenable account of the evolution of multiple cone classes.
To examine the effect of wave‐induced light fluctuations on the appearance of objects to fish, we recorded the spatial and temporal fluctuations of light reflected from a diffusely reflecting target that served as a simplified proxy for the body of a fish, and of light from the water background that a fish might be viewed against. Measurements were repeated at diverse depths, viewing azimuths, distances to the substrate, and sun conditions. Two conditions that are necessary for wave‐induced light fluctuations to make objects more apparent to fish were satisfied. The contrast of light fluctuations reflected from either the object or water background was higher than the minimum contrast value that is detected by fish, or, alternatively, the contrast of light fluctuations reflected from both the object and water background was higher than the minimum contrast value detected by fish, but differed from one another. Furthermore, the frequency range where most of the power of wave‐induced radiance fluctuations matched the frequency range of maximum contrast sensitivity in fish. Thus, light stimuli having spatial and temporal characteristics similar to those of wave‐induced light fluctuations may make objects more apparent to fish. We suggest that the frequency characteristics of the visual systems of fish were likely shaped by wave‐induced light fluctuations in aquatic ecosystems.
Retinal neurogenesis in fish facilitates cellular rearrangement throughout ontogeny, potentially allowing for optimization of the visual system to shifts in habitat and behaviour. To test this possibility, we studied the developmental trajectory of the photopic visual process in the Nile tilapia. We examined ontogenetic changes in lens transmission, photoreceptor sensitivity and post-receptoral sensitivity, and used these to estimate changes in cone pigment frequency and retinal circuitry. We observed an ontogenetic decrease in ultraviolet (UV) photoreceptor sensitivity, which resulted from a reduction in the SWS1 cone pigment frequency, and was associated with a reduction in lens transmission at UV wavelengths. Additionally, post-receptoral sensitivity to both UV and long wavelengths decreased with age, probably reflecting changes in photoreceptor sensitivity and retinal circuitry. This novel remodelling of retinal circuitry occurred following maturation of the visual system but prior to reaching adulthood, and thus may facilitate optimization of the visual system to the changing sensory demands. Interestingly, the changes in post-receptoral sensitivity to long wavelengths could not be predicted by the changes observed in lens transmission, cone pigment frequency or photoreceptor sensitivity. This finding emphasizes the importance of considering knowledge of visual sensitivity and retinal processing when studying visual adaptations and attempting to relate visual function to the natural environment. This study advances our understanding of ontogeny in visual systems and demonstrates that the association between different elements of the visual process can be explored effectively by examining visual function throughout ontogeny.
