bluuebunny/crossref_metadata_2025_split huggingface dataset:
The remarkable visual capacities of nocturnal insects: vision at the limits with small eyes and tiny brains
Authors: Warrant Eric J. 
Published: February 2017

Nocturnal insects have evolved remarkable visual capacities, despite small eyes and tiny brains. They can see colour, control flight and land, react to faint movements in their environment, navigate using dim celestial cues and find their way home after a long and tortuous foraging trip using learned visual landmarks. These impressive visual abilities occur at light levels when only a trickle of photons are being absorbed by each photoreceptor, begging the question of how the visual system nonetheless generates the reliable signals needed to steer behaviour. In this review, I attempt to provide an answer to this question. Part of the answer lies in their compound eyes, which maximize light capture. Part lies in the slow responses and high gains of their photoreceptors, which improve the reliability of visual signals. And a very large part lies in the spatial and temporal summation of these signals in the optic lobe, a strategy that substantially enhances contrast sensitivity in dim light and allows nocturnal insects to see a brighter world, albeit a slower and coarser one. What is abundantly clear, however, is that during their evolution insects have overcome several serious potential visual limitations, endowing them with truly extraordinary night vision.This article is part of the themed issue ‘Vision in dim light’.
Living in the dark does not mean a blind life: bird and mammal visual communication in dim light
Authors: Penteriani Vincenzo , Delgado María del Mar 
Published: February 2017

For many years, it was believed that bird and mammal communication ‘in the dark of the night’ relied exclusively on vocal and chemical signalling. However, in recent decades, several case studies have conveyed the idea that the nocturnal world is rich in visual information. Clearly, a visual signal needs a source of light to work, but diurnal light (twilight included, i.e. any light directly dependent on the sun) is not the only source of luminosity on this planet. Actually, moonlight represents a powerful source of illumination that cannot be neglected from the perspective of visual communication. White patches of feathers and fur on a dark background have the potential to be used to communicate with conspecifics and heterospecifics in dim light across different contexts and for a variety of reasons. Here: (i) we review current knowledge on visual signalling in crepuscular and nocturnal birds and mammals; and (ii) we also present some possible cases of birds and mammals that, due to the characteristics of their feather and fur coloration pattern, might use visual signals in dim light. Visual signalling in nocturnal animals is still an emerging field and, to date, it has received less attention than many other means of communication, including visual communication under daylight. For this reason, many questions remain unanswered and, sometimes, even unasked.This article is part of the themed issue ‘Vision in dim light’.
Thresholds and noise limitations of colour vision in dim light
Authors: Kelber Almut , Yovanovich Carola , Olsson Peter 
Published: February 2017

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’.
Seeing in the deep-sea: visual adaptations in lanternfishes
Authors: de Busserolles Fanny , Marshall N. Justin 
Published: February 2017

Ecological and behavioural constraints play a major role in shaping the visual system of different organisms. In the mesopelagic zone of the deep- sea, between 200 and 1000 m, very low intensities of downwelling light remain, creating one of the dimmest habitats in the world. This ambient light is, however, enhanced by a multitude of bioluminescent signals emitted by its inhabitants, but these are generally dim and intermittent. As a result, the visual system of mesopelagic organisms has been pushed to its sensitivity limits in order to function in this extreme environment. This review covers the current body of knowledge on the visual system of one of the most abundant and intensely studied groups of mesopelagic fishes: the lanternfish (Myctophidae). We discuss how the plasticity, performance and novelty of its visual adaptations, compared with other deep-sea fishes, might have contributed to the diversity and abundance of this family.
This article is part of the themed issue ‘Vision in dim light’.
The evolution of rod photoreceptors
Authors: Morshedian Ala , Fain Gordon L. 
Published: February 2017

Photoreceptors in animals are generally of two kinds: the ciliary or c-type and the rhabdomeric or r-type. Although ciliary photoreceptors are found in many phyla, vertebrates seem to be unique in having two distinct kinds which together span the entire range of vision, from single photons to bright light. We ask why the principal photoreceptors of vertebrates are ciliary and not rhabdomeric, and how rods evolved from less sensitive cone-like photoreceptors to produce our duplex retina. We suggest that the principal advantage of vertebrate ciliary receptors is that they use less ATP than rhabdomeric photoreceptors. This difference may have provided sufficient selection pressure for the development of a completely ciliary eye. Although many of the details of rod evolution are still uncertain, present evidence indicates that (i) rods evolved very early before the split between the jawed and jawless vertebrates, (ii) outer-segment discs make no contribution to rod sensitivity but may have evolved to increase the efficiency of protein renewal, and (iii) evolution of the rod was incremental and multifaceted, produced by the formation of several novel protein isoforms and by changes in protein expression, with no one alteration having more than a few-fold effect on transduction activation or inactivation.
This article is part of the themed issue ‘Vision in dim light’.
Functional preservation and variation in the cone opsin genes of nocturnal tarsiers
Authors: Moritz Gillian L. , Ong Perry S. , Perry George H. , Dominy Nathaniel J. 
Published: February 2017

The short-wavelength sensitive (S-) opsin geneOPN1SWis pseudogenized in some nocturnal primates and retained in others, enabling dichromatic colour vision. Debate on the functional significance of this variation has focused on dark conditions, yet many nocturnal species initiate activity under dim (mesopic) light levels that can support colour vision. Tarsiers are nocturnal, twilight-active primates and exemplary visual predators; they also express different colour vision phenotypes, raising the possibility of discrete adaptations to mesopic conditions. To explore this premise, we conducted a field study in two stages. First, to estimate the level of functional constraint on colour vision, we sequencedOPN1SWin 12 wild-caught Philippine tarsiers (Tarsius syrichta). Second, to explore whether the dichromatic visual systems of Philippine and Bornean (Tarsius bancanus) tarsiers—which express alternate versions of the medium/long-wavelength sensitive (M/L-) opsin geneOPN1MW/OPN1LW—confer differential advantages specific to their respective habitats, we used twilight and moonlight conditions to model the visual contrasts of invertebrate prey. We detected a signature of purifying selection forOPN1SW, indicating that colour vision confers an adaptive advantage to tarsiers. However, this advantage extends to a relatively small proportion of prey–background contrasts, and mostly brown arthropod prey amid leaf litter. We also found that the colour vision ofT. bancanusis advantageous for discriminating prey under twilight that is enriched in shorter (bluer) wavelengths, a plausible idiosyncrasy of understorey habitats in Borneo.This article is part of the themed issue ‘Vision in dim light’.
Comparative system identification of flower tracking performance in three hawkmoth species reveals adaptations for dim light vision
Authors: Stöckl Anna L. , Kihlström Klara , Chandler Steven , Sponberg Simon 
Published: February 2017

Flight control in insects is heavily dependent on vision. Thus, in dim light, the decreased reliability of visual signal detection also prompts consequences for insect flight. We have an emerging understanding of the neural mechanisms that different species employ to adapt the visual system to low light. However, much less explored are comparative analyses of how low light affects the flight behaviour of insect species, and the corresponding links between physiological adaptations and behaviour. We investigated whether the flower tracking behaviour of three hawkmoth species with different diel activity patterns revealed luminance-dependent adaptations, using a system identification approach. We found clear luminance-dependent differences in flower tracking in all three species, which were explained by a simple luminance-dependent delay model, which generalized across species. We discuss physiological and anatomical explanations for the variance in tracking responses, which could not be explained by such simple models. Differences between species could not be explained by the simple delay model. However, in several cases, they could be explained through the addition on a second model parameter, a simple scaling term, that captures the responsiveness of each species to flower movements. Thus, we demonstrate here that much of the variance in the luminance-dependent flower tracking responses of hawkmoths with different diel activity patterns can be captured by simple models of neural processing.This article is part of the themed issue ‘Vision in dim light’.
Stellar performance: mechanisms underlying Milky Way orientation in dung beetles
Authors: Foster James J. , el Jundi Basil , Smolka Jochen , Khaldy Lana , Nilsson Dan-Eric , Byrne Marcus J. , Dacke Marie 
Published: February 2017

Nocturnal dung beetles (Scarabaeus satyrus) are currently the only animals that have been demonstrated to use the Milky Way for reliable orientation. In this study, we tested the capacity ofS. satyrusto orient under a range of artificial celestial cues, and compared the properties of these cues with images of the Milky Way simulated for a beetle's visual system. We find that the mechanism that permits accurate stellar orientation under the Milky Way is based on an intensity comparison between different regions of the Milky Way. We determined the beetles' contrast sensitivity for this task in behavioural experiments in the laboratory, and found that the resulting threshold of 13% is sufficient to detect the contrast between the southern and northern arms of the Milky Way under natural conditions. This mechanism should be effective under extremely dim conditions and on nights when the Milky Way forms a near symmetrical band that crosses the zenith. These findings are discussed in the context of studies of stellar orientation in migratory birds and itinerant seals.This article is part of the themed issue ‘Vision in dim light’.
Can model-free reinforcement learning operate over information stored in working-memory?
Authors: da Silva Carolina Feher , Yao Yuan-Wei , Hare Todd A. 
Published: February 2017

AbstractModel-free learning creates stimulus-response associations. But what constitutes a stimulus? Are there limits to types of stimuli a model-free or habitual system can operate over? Most experiments on reward learning in humans and animals have used discrete sensory stimuli, but there is no algorithmic reason that model-free learning should be restricted to external stimuli, and recent theories have suggested that model-free processes may operate over highly abstract concepts and goals. Our study aimed to determine whether model-free learning processes can operate over environmental states defined by information held in working memory. Specifically, we tested whether or not humans can learn explicit temporal patterns of individually uninformative cues in a model-free manner. We compared the data from human participants in a reward learning paradigm using (1) a simultaneous symbol presentation condition or (2) a sequential symbol presentation condition, wherein the same visual stimuli were presented simultaneously or as a temporal sequence that required working memory. We found a significant effect of reward on human behavior in the sequential presentation condition, indicating that model-free learning can operate on information stored in working memory. Further analyses, however, revealed that the behavior of the participants contradicts the basic assumptions of our hypotheses, and it is possible that the observed effect of reward was generated by model-based rather than model-free learning. Thus it is not possible to draw any conclusions from out study regarding model-free learning of temporal sequences held in working memory. We conclude instead that careful thought should be given about how to best explain two-stage tasks to participants.
VICTOR: Genome-based Phylogeny and Classification of Prokaryotic Viruses
Authors: Meier-Kolthof Jan P. , Göker Markus 
Published: February 2017

AbstractBacterial and archaeal viruses (“phages”) play an enormous role in global life cycles and have recently regained importance as therapeutic agents to fight serious infections by multi-resistant bacterial strains. Nevertheless, taxonomic classification of phages is up to now only insufficiently informed by genome sequencing. Despite thousands of publicly available phage genomes, it still needs to be investigated how this wealth of information can be used for the fast, universal and accurate classification of phages. The Genome BLAST Distance Phylogeny (GBDP) approach is a truly whole-genome method currently used forin silicoDNA: DNA hybridization and phylogenetic inference from prokaryotic genomes. Based on the principles of phylogenetic systematics, we here established GBDP for phage phylogeny and classification, using the common subset of genome-sequenced and officially classified phages. Trees inferred with the best GBDP variants showed only few deviations from the official phage classification, which were uniformly due to incorrectly annotated GenBank entries. Except for low resolution at the family level, the majority of taxa was well supported as monophyletic. Clustering genome sequences with distance thresholds optimized for the agreement with the classification turned out to be phylogenetically reasonable. Accordingly modifying genera and species is taxonomically optional but would yield more uniform sequence divergence as well as stronger branch support. Analysing an expanded data set containing > 4000 phage genomes from public databases allowed for extrapolating regarding the number, composition and host specificity of future phage taxa. The selected methods are implemented in an easy-to-use web service “VICTOR” freely available athttp://ggdc.dsmz.de/victor.php.
Inferring decoding strategies for multiple correlated neural populations
Authors: Lakshminarasimhan Kaushik J , Pouget Alexandre , DeAngelis Gregory C , Angelaki Dora E , Pitkow Xaq 
Published: February 2017

AbstractStudies of neuron-behaviour correlation and causal manipulation have long been used separately to understand the neural basis of perception. Yet these approaches sometimes lead to drastically conflicting conclusions about the functional role of brain areas. Theories that focus only on choice-related neuronal activity cannot reconcile those findings without additional experiments involving large-scale recordings to measure interneuronal correlations. By expanding current theories of neural coding and incorporating results from inactivation experiments, we demonstrate here that it is possible to infer decoding weights of different brain areas without precise knowledge of the correlation structure. We apply this technique to neural data collected from two different cortical areas in macaque monkeys trained to perform a heading discrimination task. We identify two opposing decoding schemes, each consistent with data depending on the nature of correlated noise. Our theory makes specific testable predictions to distinguish these scenarios experimentally without requiring measurement of the underlying noise correlations.Author SummaryThe neocortex is structurally organized into distinct brain areas. The role of specific brain areas in sensory perception is typically studied using two kinds of laboratory experiments: those that measure correlations between neural activity and reported percepts, and those that inactivate a brain region and measure the resulting changes in percepts. The two types of experiments have generally been interpreted in isolation, in part because no theory has been able combine their outcomes. Here, we describe a mathematical framework that synthesizes both kinds of results, giving us a new way to assess how different brain areas contribute to perception. When we apply our framework to experiments on behaving monkeys, we discover two models that can explain the perplexing finding that one brain area can predict an animal’s percepts, even though the percepts are not affected when that brain area is inactivated. The two models ascribe dramatically different efficiencies to brain computation. We show that these two models can be distinguished by an experiment that measures correlations while inactivating different brain areas.
Uncharacterized bacterial structures revealed by electron cryotomography
Authors: Dobro Megan J. , Oikonomou Catherine M. , Piper Aidan , Cohen John , Guo Kylie , Jensen Taylor , Tadayon Jahan , Donermeyer Joseph , Park Yeram , Solis Benjamin A. , Kjær Andreas , Jewett Andrew I. , McDowall Alasdair W. , Chen Songye , Chang Yi-Wei , Shi Jian , Subramanian Poorna , Iancu Cristina V. , Li Zhuo , Briegel Ariane , Tocheva Elitza I. , Pilhofer Martin , Jensen Grant J. 
Published: February 2017

SUMMARY STATEMENTHere we present a survey of previously uncharacterized structures we have observed in bacterial cells by electron cryotomography, in the hopes of spurring their identification and study.ABSTRACTElectron cryotomography (ECT) can reveal the native structure and arrangement of macromolecular complexes inside intact cells. This technique has greatly advanced our understanding of the ultrastructure of bacterial cells. Rather than undifferentiated bags of enzymes, we now view bacteria as structurally complex assemblies of macromolecular machines. To date, our group has applied ECT to nearly 90 different bacterial species, collecting more than 15,000 cryotomograms. In addition to known structures, we have observed several, to our knowledge, uncharacterized features in these tomograms. Some are completely novel structures; others expand the features or species range of known structure types. Here we present a survey of these uncharacterized bacterial structures in the hopes of accelerating their identification and study, and furthering our understanding of the structural complexity of bacterial cells.
Predisposition towards foreign brands and materialism: a quantitative assessment
Authors: Vohra Aastha Verma , Gupta Garima 
Published: February 2017

Purpose
The purpose of this paper is to identify the dimensions of predisposition towards foreign brands (PTFB) for Indian consumers and examine their impact on materialism/materialist value (MAT). The study further conducts an in-depth analysis of these constructs for possible variations across consumer demographics.

Design/methodology/approach
Using a structured questionnaire, primary data were collected from 487 respondents in the city of Delhi and National Capital Region (NCR). While a modified scale was developed to operationalize PTFB, the measurement instrument for MAT was adapted on the basis of an extensive literature review. Statistical techniques such as Exploratory factor analysis, Confirmatory factor analysis, t-test, analysis of variance (ANOVA) and regression analysis were used to test various hypotheses of the study.

Findings
The study identified five dimensions of PTFB, namely, “Reputation”, “Preference”, “Country of Origin”, “Accessibility” and “Quality”, through confirmatory factor analysis in structural equation modelling. Except for “Preference” and “Accessibility”, all remaining dimensions were found to be exerting a significant impact on MAT. The results further indicate that consumers’ PTFB as well as their MAT differs across demographics such as age, income, gender, occupation and qualification.

Practical implications
The paper brings to the fore useful insights for marketers of foreign brands. The findings can be effectively used for developing a more focused marketing strategy for Indian consumers by helping in identifying demographic segments that are more responsive and susceptible to the entry of foreign brands in Indian markets.

Originality/value
The paper attempts to develop a more robust instrument for measurement of consumers’ PTFB and provides dimensions constituting the construct for consumers of emerging markets such as India. The current research also indicates that there exists a significant variation in PTFB and MAT for different demographic segments of consumers.
Patient satisfaction and brand loyalty in health-care organizations in India
Authors: Sharma Vinay 
Published: February 2017

PurposeThis paper aims to examine the major factors affecting patients’ satisfaction and loyalty at a health-care organization in India.Design/methodology/approachA conceptual model has been developed that includes the behavioural dimensions of total quality management (TQM), patient satisfaction and loyalty. This study is exploratory in nature and has used the existing literature to build the conceptual model.FindingsA solution for improving the quality of health-care services can be found in the application of total relationship management and TQM, together with a customer orientation strategy.Practical implicationsThe results can be used creatively by hospitals to re-engineer and redesign their quality management processes and reorient the future directions of their more effective health-care quality strategies.Originality/valueIn this research, a study is described involving a new instrument and a new method which assure a reasonable level of relevance, validity and reliability, while being explicitly change-oriented.