Characterization and use of a digital light projector for vision research

For creating stimuli in the laboratory, digital light projection (DLP) technology has the potential to overcome the low output luminance, lack of pixel independence, and limited chromaticity gamut of the cathode ray tube (CRT). We built a DLP-based stimulator for projecting patterns on the in vitro primate retina. The DLP produces high light levels and has good contrast. Spatial performance was similar to that of a CRT. Temporal performance was limited by the refresh rate (63 Hz). The chromatic gamut was modestly larger than that of a CRT although the primary spectra varied to a small degree with light output and numerical aperture.     

Light visor treatment for jet lag after westward travel across six time zones

INTRODUCTION: The aim of this field study was to evaluate the efficacy of a light treatment for jet lag, using a head-mounted light visor, following a westward flight across six time zones. METHODS: There were 20 subjects who were exposed to bright white light (3000 lux) or dim red light (10 lux) for 3 h on the first two evenings after a flight from Zurich to New York. Salivary dim light melatonin onset (DLMO), assessed 2 d before and 2 d after the flight, provided a measure of circadian phase. Sleep was recorded by actigraphy, while post-flight performance testing and subjective scales provided additional indices of jet lag severity. RESULTS: The DLMO measurements showed a larger phase delay in the bright light than in the dim light group (2.59 h vs. 1.58 h, p < 0.02). There was no overall difference in sleep efficiency (SE) between the two groups, but a significant Group x Night interaction reflected a small increase across the first two post-flight nights in the bright light group, and a small decrease in the dim light group. Reaction time on one of two performance tests was consistently faster in the dim light group, but was unrelated to circadian phase or to prior sleep. There were no major group differences in subjective sleep quality, daytime sleepiness, jet lag severity, or mood. DISCUSSION: This is the first full-scale study to show that bright light treatment can accelerate circadian reentrainment following transmeridian travel. However, the effect on reentrainment rate was modest, and was not accompanied by any improvement in sleep, performance, or subjective assessments of jet lag symptoms.     

Commonness and rarity in the marine biosphere

Explaining patterns of commonness and rarity is fundamental for understanding and managing biodiversity. Consequently, a key test of biodiversity theory has been how well ecological models reproduce empirical distributions of species abundances. However, ecological models with very different assumptions can predict similar species abundance distributions, whereas models with similar assumptions may generate very different predictions. This complicates inferring processes driving community structure from model fits to data. Here, we use an approximation that captures common features of “neutral” biodiversity models—which assume ecological equivalence of species—to test whether neutrality is consistent with patterns of commonness and rarity in the marine biosphere. We do this by analyzing 1,185 species abundance distributions from 14 marine ecosystems ranging from intertidal habitats to abyssal depths, and from the tropics to polar regions. Neutrality performs substantially worse than a classical nonneutral alternative: empirical data consistently show greater heterogeneity of species abundances than expected under neutrality. Poor performance of neutral theory is driven by its consistent inability to capture the dominance of the communities’ most-abundant species. Previous tests showing poor performance of a neutral model for a particular system often have been followed by controversy about whether an alternative formulation of neutral theory could explain the data after all. However, our approach focuses on common features of neutral models, revealing discrepancies with a broad range of empirical abundance distributions. These findings highlight the need for biodiversity theory in which ecological differences among species, such as niche differences and demographic trade-offs, play a central role.Determining how biodiversity is maintained in ecological communities is a long-standing ecological problem. In species-poor communities, niche and demographic differences between species can often be estimated directly and used to infer the importance of alternative mechanisms of species coexistence (1–3). However, the “curse of dimensionality” prevents the application of such species-by-species approaches to high-diversity assemblages: the number of parameters in community dynamics models increases more rapidly than the amount of data, as species richness increases. Moreover, most species in high-diversity assemblages are very rare, further complicating the estimation of strengths of ecological interactions among species, or covariation in different species’ responses to environmental fluctuations. Consequently, ecologists have focused instead on making assumptions about the overall distribution of demographic rates, niche sizes, or other characteristics of an assemblage, and then deriving the aggregate assemblage properties implied by those assumptions (4–8). One of the most commonly investigated of these assemblage-level properties is the species abundance distribution (SAD)—the pattern of commonness and rarity among species (9–11). Ecologists have long sought to identify mechanisms that can explain common features of, and systematic differences among, the shapes of such distributions, and have used the ability to reproduce empirical SADs as a key test of biodiversity theory in species-rich systems (4, 6, 11–14).Over the last decade, one of the most prevalent and influential approaches to explaining the structure of high-diversity assemblages has been neutral theory of biodiversity (12, 15, 16). Neutral models assume that individuals are demographically and ecologically equivalent, regardless of species. Thus, variation in relative abundance among species arises purely from demographic stochasticity: chance variation in the fates of individuals (i.e., birth, death, immigration, and speciation events). Most studies investigating neutral theory aim to determine whether community structure in nature is consistent with the theory’s core species equivalence assumption. This is typically done by assessing the fit of a neutral model to empirical data, sometimes relative to a putatively nonneutral alternative (17–20). However, although all neutral models share the species equivalence assumption, they differ with respect to auxiliary assumptions, such as the mode of speciation assumed, leading to different predictions for SADs and other ecological patterns. Indeed, attempts to draw conclusions from tests of neutral theory are almost invariably disputed, largely due to arguments about the extent to which alternative auxiliary assumptions can materially alter neutral theory’s ability to explain the data (11, 12, 18, 21).An alternative, potentially more robust approach to evaluating neutral theory was proposed by Pueyo (22), based on approximating neutral and nonneutral dynamics as successively higher-order perturbations of a model for the idealized case of pure random drift in abundances. This approach predicts that a gamma distribution should approximate the distribution of species abundances for small departures for random drift, whereas assemblages exhibiting greater departures from neutrality should be better approximated by a lognormal distribution. This raises the possibility that a comparison of gamma and lognormal SADs could offer a robust test for the signature of nonneutrality in species abundance data, provided that the gamma distribution provides a sufficiently close approximation to SADs produced by neutral models.Here, we evaluate Pueyo’s framework and apply it to patterns of commonness and rarity in 1,185 SADs from 14 marine ecosystems ranging from shallow reef platforms to abyssal depths, and from the tropics to polar regions (Fig. 1 and Tables S1 and S2). First, we test the gamma neutral approximation against several models of community dynamics that share the core neutrality assumption of species equivalence, but make different assumptions about the speciation process, spatial structure of the metacommunity, and the nature of competition between individuals. Then, we analyze the marine species abundance data, to evaluate whether they are consistent with the hypothesis that marine assemblages are neutrally structured. Finally, we ask whether patterns of commonness and rarity deviate from neutral expectation in idiosyncratic ways, or whether there are particular features of real SADs that cannot be captured by neutral models.Open in a separate windowFig. 1.Sampling locations of SADs. Color and symbol combinations correspond to particular ecosystems. These symbols are reproduced in the surrounding panels, which show observed and fitted SADs for the site-level data (averaged across sites) of the corresponding ecosystem. The bars represent the mean proportion of species at each site in different octave classes of abundance, across all sites in the corresponding dataset [the first bar represents species with abundance 1, then abundances 2–3, abundances 4–7, etc. (10)]. The blue and red lines show the mean of fitted values from site-by-site fits of the Poisson-gamma and Poisson-lognormal distributions to the data, respectively.     

Clinical pharmacology profile of raltegravir, an HIV-1 integrase strand transfer inhibitor

Raltegravir is an HIV-1 integrase inhibitor approved to treat HIV infection in adults in combination with other antiretrovirals. Data from healthy volunteers demonstrate that raltegravir is rapidly absorbed with a mean half-life of approximately 7 to 12 hours, with steady state achieved in approximately 2 days. Raltegravir is characterized by both high intra- and interindividual variabilities, although neither gender, race, age, body mass index, food intake, nor renal or hepatic insufficiency has a clinically meaningful effect on raltegravir pharmacokinetics. Raltegravir lacks activity as a perpetrator of drug-drug interactions and demonstrates a low propensity to be subject to drug-drug interactions. Raltegravir is metabolized primarily by UGT1A1 and is not affected by P450 inhibitors or inducers. Inhibitors of UGT1A1 (eg, atazanavir) can increase plasma concentrations of raltegravir, although this increase has not been found to be clinically meaningful. Likewise, inducers of UGT1A1 (eg, rifampin) can reduce plasma concentrations of raltegravir, and the clinical significance of this reduction is being investigated in ongoing clinical studies. Raltegravir demonstrates favorable clinical pharmacology and a drug interaction profile that permits administration to a wide, demographically diverse patient population and coadministration with many other therapeutic agents, including antiretroviral agents and supportive medications, without restrictions or dose adjustment.     

Cardiomyopathy and right-sided congestive heart failure in a red-tailed hawk (Buteo jamaicensis)

A 15-year-old female red-tailed hawk (Buteo jamaicensis) was evaluated because of dyspnea, anorexia, and coelomic distension. Diagnostic imaging results confirmed severe coelomic effusion and revealed a markedly dilated right ventricle. The diagnosis was right-sided congestive heart failure. Results of measurements of vitamin E, selenium, lead, zinc, and cardiac troponin levels were normal or nondiagnostic. The hawk was treated with furosemide, antifungal and antimicrobial agents, and supplemental fluids and oxygen, but euthanasia was elected because of the poor prognosis and the practical difficulties associated with intensive case management. To our knowledge, this is the first described case of cardiomyopathy and congestive heart failure in a captive red-tailed hawk.     

Lesions of an avian basal ganglia circuit prevent context-dependent changes to song variability

Trial-by-trial variability is important in feedback-based motor learning. Variation in motor output enables evaluation mechanisms to differentially reinforce patterns of motor activity that produce desired behaviors. Here, we studied neural substrates of variability in the performance of adult birdsong, a complex, learned motor skill used for courtship. Song performance is more variable when male birds sing alone (undirected) than when they sing to females (directed). We test the role of the anterior forebrain pathway (AFP), an avian basal ganglia-forebrain circuit, in this socially driven modulation of song variability. We show that lesions of the lateral magnocellular nucleus of the anterior nidopallium (LMAN), the output nucleus of the AFP, cause a reduction in the moment-by-moment variability in syllable structure during undirected song to the level present during directed song. This elimination of song modulation is immediate and long-lasting. We further show that the degree of syllable variability and its modulation are both attenuated in older birds, in concert with decreased variability of LMAN activity in these birds. In contrast to the requirement of LMAN for social modulation of syllable structure, we find that LMAN is not required for modulation of other features of song, such as the number of introductory elements and motif repetitions and the ordering of syllables or for other motor and motivational aspects of courtship. Our findings suggest that a key function of avian basal ganglia circuitry is to regulate vocal performance and plasticity by specifically modulating moment-by-moment variability in the structure of individual song elements.     

Short-wavelength sensitivity for the direct effects of light on alertness, vigilance, and the waking electroencephalogram in humans

STUDY OBJECTIVES: To assess the wavelength-dependent sensitivity of the acute effects of ocular light exposure on alertness, performance, waking electroencephalogram (EEG), and cortisol. DESIGN: A between-subjects design was employed to compare the effects of exposure to 460-nm or 555-nm light for 6.5 hours during the biological night. SETTING: Intensive Physiological Monitoring Unit, Brigham and Women's Hospital, Boston, MA. PATIENTS AND PARTICIPANTS: Sixteen healthy adults (8 women; mean age +/- SD = 23.3 +/- 2.4 years). INTERVENTIONS: Subjects were exposed to equal photon densities (2.8 x 10(13) photons x cm(-2) x s(-1)) of either 460-nm (n = 8) or 555-nm (n = 8) monochromatic light for 6.5 hours, 15 minutes after mydriasis. MEASUREMENTS AND RESULTS: Subjects underwent continuous EEG/electrooculogram recordings and completed a performance battery every 30 to 60 minutes. As compared with those exposed to 555-nm light, subjects exposed to 460-nm light had significantly lower subjective sleepiness ratings, decreased auditory reaction time, fewer attentional failures, decreased EEG power density in the delta-theta range (0.5-5.5 Hz), and increased EEG power density in the high-alpha range (9.5-10.5 Hz). Light had no direct effect on cortisol. CONCLUSIONS: Short-wavelength sensitivity to the acute alerting effects of light indicates that the visual photopic system is not the primary photoreceptor system mediating these responses to light. The frequency-specific changes in the waking EEG indicate that short-wavelength light is a powerful agent that immediately attenuates the negative effects of both homeostatic sleep pressure and the circadian drive for sleep on alertness, performance, and the ability to sustain attention.     

Feasibility and evaluation of an emergency department-based general practitioner streaming and treatment service

Rationale

Offering a primary care service that can provide good quality primary care at emergency departments may reduce pressure on usual emergency department (ED) services.

Aims and Objectives

To evaluate the acceptability, satisfaction, and potential impacts of a co-located primary care service at an emergency department.

Methods

This is a prospective feasibility study and service evaluation comprising a narrative summary of activity, satisfaction, well-being, and safety, and comparisons of wait times for ED services by patient category (‘minor’, ‘majors’, ‘paediatric’ or ‘resus’) before and during the service operation. Patients and staff were asked using semistructured interview topic guides about service perception, well-being, representation within 48 h, safety concerns, and/or satisfaction. Wait times for patient categories in usual ED care service were in secondary care electronic records. Pathway changes were captured under primary care electronic records.

Results

Approximately 96% of general practitioner streaming and treatment (GPST) patients were seen within 1 h. There was a statistically significant reduction in ED patients with minor injuries or illnesses waiting >4 h for admission or discharge ‘breaches’ during the 3 months that GPST was operating compared with the previous 3 months (p ≤ 0.005). Wait times for other ED services did not significantly improve. A total of 769 walk-in patients received GPST consultation and 661 (86%) needed no further ED intervention. Fast discharge was a major determinant of patient satisfaction. No staff expressed dissatisfaction, but some suggested possible improvements in eligibility criteria and built environment design features.

Conclusion

Provision of GPST correlated with shorter waits for discharge from ED. Patient and staff experiences of GPST were positive.