Local Axonal Conduction Shapes the Spatiotemporal Properties of Neural Sequences.

Sequential activation of neurons has been observed during various behavioral and cognitive processes, but the underlying circuit mechanisms remain poorly understood. Here, we investigate premotor sequences in HVC (proper name) of the adult zebra finch forebrain that are central to the performance of the temporally precise courtship song. We use high-density silicon probes to measure song-related population activity, and we compare these observations with predictions from a range of network models. Our results support a circuit architecture in which heterogeneous delays between sequentially active neurons shape the spatiotemporal patterns of HVC premotor neuron activity. We gauge the impact of several delay sources, and we find the primary contributor to be slow conduction through axonal collaterals within HVC, which typically adds between 1 and 7.5 ms for each link within the sequence. Thus, local axonal "delay lines" can play an important role in determining the dynamical repertoire of neural circuits.

A Theoretical Framework for Human and Nonhuman Vocal Interaction.

Vocal communication is a critical feature of social interaction across species; however, the relation between such behavior in humans and nonhumans remains unclear. To enable comparative investigation of this topic, we review the literature pertinent to interactive language use and identify the superset of cognitive operations involved in generating communicative action. We posit these functions comprise three intersecting multistep pathways: (a) the Content Pathway, which selects the movements constituting a response; (b) the Timing Pathway, which temporally structures responses; and (c) the Affect Pathway, which modulates response parameters according to internal state. These processing streams form the basis of the Convergent Pathways for Interaction framework, which provides a conceptual model for investigating the cognitive and neural computations underlying vocal communication across species.

Thalamus drives vocal onsets in the zebra finch courtship song.

While motor cortical circuits contain information related to specific movement parameters1, long-range inputs also have a critical role in action execution2,3. Thalamic projections can shape premotor activity2-6 and have been suggested7 to mediate the selection of short, stereotyped actions comprising more complex behaviours8. However, the mechanisms by which thalamus interacts with motor cortical circuits to execute such movement sequences remain unknown. Here we find that thalamic drive engages a specific subpopulation of premotor neurons within the zebra finch song nucleus HVC (proper name) and that these inputs are critical for the progression between vocal motor elements (that is, 'syllables'). In vivo two-photon imaging of thalamic axons in HVC showed robust song-related activity, and online perturbations of thalamic function caused song to be truncated at syllable boundaries. We used thalamic stimulation to identify a sparse set of thalamically driven neurons within HVC, representing ~15% of the premotor neurons within that network. Unexpectedly, this population of putative thalamorecipient neurons is robustly active immediately preceding syllable onset, leading to the possibility that thalamic input can initiate individual song components through selectively targeting these 'starter cells'. Our findings highlight the motor thalamus as a director of cortical dynamics in the context of an ethologically relevant behavioural sequence.

A speech planning network for interactive language use.

During conversation, people take turns speaking by rapidly responding to their partners while simultaneously avoiding interruption1,2. Such interactions display a remarkable degree of coordination, as gaps between turns are typically about 200 milliseconds3-approximately the duration of an eyeblink4. These latencies are considerably shorter than those observed in simple word-production tasks, which indicates that speakers often plan their responses while listening to their partners2. Although a distributed network of brain regions has been implicated in speech planning5-9, the neural dynamics underlying the specific preparatory processes that enable rapid turn-taking are poorly understood. Here we use intracranial electrocorticography to precisely measure neural activity as participants perform interactive tasks, and we observe a functionally and anatomically distinct class of planning-related cortical dynamics. We localize these responses to a frontotemporal circuit centred on the language-critical caudal inferior frontal cortex10 (Broca's region) and the caudal middle frontal gyrus-a region not normally implicated in speech planning11-13. Using a series of motor tasks, we then show that this planning network is more active when preparing speech as opposed to non-linguistic actions. Finally, we delineate planning-related circuitry during natural conversation that is nearly identical to the network mapped with our interactive tasks, and we find this circuit to be most active before participant speech during unconstrained turn-taking. Therefore, we have identified a speech planning network that is central to natural language generation during social interaction.

The Inverted Case Study Technique: changing the traditional case-study approach to prioritize physiological mechanisms over correct diagnosis and treatment.

The traditional case study has been used as a learning tool for the past 100 years, and in our program, graduate physiology students are presented with a real-world scenario and must determine the diagnosis and treatment of the patient. We found that students defaulted to memorization of disease with treatment and bypassed gaining an understanding of the mechanistic physiology behind disease and treatment. To adjust our student's approach, we developed a novel way to enhance student learning. To accomplish this shift from memorization to physiological mastery, we created the Inverted Case Study. This approach diverges from the traditional model in that students are given the diagnosis and treatment beforehand and are tasked with explaining the actual physiology of the case. In this way, students can no longer rely on the memorization of symptoms-disease-treatment but rather gain a solid understanding of the physiological mechanisms of the disease since that is the focus of the Inverted Case Study Technique. The Inverted Case Study approach is an effective approach to apply and hone critical thinking skills.NEW & NOTEWORTHY This article presents a novel approach to century-old learning techniques that enhances students' self-reported learning and also their attitudes toward learning mechanistic physiology and increases their perception of preparedness for professional school.

De novo assembly and annotation of the singing mouse genome.

BACKGROUND: Developing genomic resources for a diverse range of species is an important step towards understanding the mechanisms underlying complex traits. Specifically, organisms that exhibit unique and accessible phenotypes-of-interest allow researchers to address questions that may be ill-suited to traditional model organisms. We sequenced the genome and transcriptome of Alston's singing mouse (Scotinomys teguina), an emerging model for social cognition and vocal communication. In addition to producing advertisement songs used for mate attraction and male-male competition, these rodents are diurnal, live at high-altitudes, and are obligate insectivores, providing opportunities to explore diverse physiological, ecological, and evolutionary questions. RESULTS: Using PromethION, Illumina, and PacBio sequencing, we produced an annotated genome and transcriptome, which were validated using gene expression and functional enrichment analyses. To assess the usefulness of our assemblies, we performed single nuclei sequencing on cells of the orofacial motor cortex, a brain region implicated in song coordination, identifying 12 cell types. CONCLUSIONS: These resources will provide the opportunity to identify the molecular basis of complex traits in singing mice as well as to contribute data that can be used for large-scale comparative analyses.

Projected U.S. State-Level Prevalence of Adult Obesity and Severe Obesity.

BACKGROUND: Although the national obesity epidemic has been well documented, less is known about obesity at the U.S. state level. Current estimates are based on body measures reported by persons themselves that underestimate the prevalence of obesity, especially severe obesity. METHODS: We developed methods to correct for self-reporting bias and to estimate state-specific and demographic subgroup-specific trends and projections of the prevalence of categories of body-mass index (BMI). BMI data reported by 6,264,226 adults (18 years of age or older) who participated in the Behavioral Risk Factor Surveillance System Survey (1993-1994 and 1999-2016) were obtained and corrected for quantile-specific self-reporting bias with the use of measured data from 57,131 adults who participated in the National Health and Nutrition Examination Survey. We fitted multinomial regressions for each state and subgroup to estimate the prevalence of four BMI categories from 1990 through 2030: underweight or normal weight (BMI [the weight in kilograms divided by the square of the height in meters], <25), overweight (25 to <30), moderate obesity (30 to <35), and severe obesity (≥35). We evaluated the accuracy of our approach using data from 1990 through 2010 to predict 2016 outcomes. RESULTS: The findings from our approach suggest with high predictive accuracy that by 2030 nearly 1 in 2 adults will have obesity (48.9%; 95% confidence interval [CI], 47.7 to 50.1), and the prevalence will be higher than 50% in 29 states and not below 35% in any state. Nearly 1 in 4 adults is projected to have severe obesity by 2030 (24.2%; 95% CI, 22.9 to 25.5), and the prevalence will be higher than 25% in 25 states. We predict that, nationally, severe obesity is likely to become the most common BMI category among women (27.6%; 95% CI, 26.1 to 29.2), non-Hispanic black adults (31.7%; 95% CI, 29.9 to 33.4), and low-income adults (31.7%; 95% CI, 30.2 to 33.2). CONCLUSIONS: Our analysis indicates that the prevalence of adult obesity and severe obesity will continue to increase nationwide, with large disparities across states and demographic subgroups. (Funded by the JPB Foundation.).

An investigation of the control of quadriceps in people who are hypermobile; a case control design. Do the results impact our choice of exercise for people with symptomatic hypermobility?

BACKGROUND: People with symptomatic hypermobility have altered proprioception however, the origin of this is unclear and needs further investigation to target rehabilitation appropriately. The objective of this investigation was to explore the corticospinal and reflex control of quadriceps and see if it differed between three groups of people: those who have symptomatic hypermobility, asymptomatic hypermobility and normal flexibility. METHODS: Using Transcranial Magnetic Stimulation (TMS) and electrical stimulation of peripheral nerves, motor evoked potentials (MEPs) and Hoffman (H) reflexes of quadriceps were evoked in the three groups of people. The threshold and latency of MEPs and the slope of the input-output curves and the amplitude of MEPs and H reflexes were compared across the groups. RESULTS: The slope of the input-output curve created from MEPs as a result of TMS was steeper in people with symptomatic hypermobility when compared to asymptomatic and normally flexible people (p = 0.04). There were no other differences between the groups. CONCLUSION: Corticospinal excitability and the excitability at the motoneurone pool are not likely candidates for the origin of proprioceptive loss in people with symptomatic hypermobility. This is discussed in the light of other work to suggest the receptor sitting in hypermobile connective tissue is a likely candidate. This suggests that treatment aimed at improving receptor responsiveness through increasing muscle tone, may be an effective rehabilitation strategy.

Seated Position Does Not Change Lumbar Dimensions Compared With Lateral Position.

OBJECTIVE: The infant lumbar puncture (LP) can be a technically challenging procedure. Understanding the anatomical lumbar dimensions may optimize LP conditions. Data from preterm neonates, older children, and adults indicate measurements of the lumbar spine in the seated LP position may be superior when compared with the lateral position. We use point-of-care ultrasound (US) to determine if the seated position, when compared with the lateral decubitus position, significantly affected the lumbar dimensions of infants 12 months or younger presenting to the pediatric emergency department. METHODS: We conducted a prospective observational study of a convenience sample of patients 12 months or younger. We used US to obtain 3 still images oriented longitudinally in the midline over the L3 to L4 interspace in the lateral decubitus and seated positions. A US fellowship-trained emergency physician, blinded to patient position, measured interspinous space, subarachnoid space width, and spinal canal depth. We then compared the means of all 3 dimensions in the lateral and seated positions. RESULTS: From 50 subjects, 49 subjects provided 46 evaluable sets of images for each measure. Interspinous space, spinal canal depth, and subarachnoid space width did not differ significantly between positions. Mean differences did not exceed 0.02 cm for any of the measured dimensions. We report no significant differences in the 3 lumbar dimensions at the seated position when compared with the lateral decubitus position. CONCLUSIONS: For infants younger than 12 months, sonographic measurements of lumbar dimensions did not differ between the positions commonly used for LP.

An optimized QF-binary expression system for use in zebrafish.

The zebrafish model organism has been of exceptional utility for the study of vertebrate development and disease through the application of tissue-specific labelling and overexpression of genes carrying patient-derived mutations. However, there remains a need for a binary expression system that is both non-toxic and not silenced over animal generations by DNA methylation. The Q binary expression system derived from the fungus Neurospora crassa is ideal, because the consensus binding site for the QF transcription factor lacks CpG dinucleotides, precluding silencing by CpG-meditated methylation. To optimize this system for zebrafish, we systematically tested several variants of the QF transcription factor: QF full length; QF2, which lacks the middle domain; QF2w, which is an attenuated version of QF2; and chimeric QFGal4. We found that full length QF and QF2 were strongly toxic to zebrafish embryos, QF2w was mildly toxic, and QFGal4 was well tolerated, when injected as RNA or expressed ubiquitously from stable transgenes. In addition, QFGal4 robustly activated a Tg(QUAS:GFPNLS) reporter transgene. To increase the utility of this system, we also modified the QF effector sequence termed QUAS, which consists of five copies of the QF binding site. Specifically, we decreased both the CpG dinucleotide content, as well as the repetitiveness of QUAS, to reduce the risk of transgene silencing via CpG methylation. Moreover, these modifications to QUAS removed leaky QF-independent neural expression that we detected in the original QUAS sequence. To demonstrate the utility of our QF optimizations, we show how the Q-system can be used for lineage tracing using a Cre-dependent Tg(ubi:QFGal4-switch) transgene. We also demonstrate that QFGal4 can be used in transient injections to tag and label endogenous genes by knocking in QFGal4 into sox2 and ubiquitin C genes.

mapMECFS: a portal to enhance data discovery across biological disciplines and collaborative sites.

BACKGROUND: Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating disease which involves multiple body systems (e.g., immune, nervous, digestive, circulatory) and research domains (e.g., immunology, metabolomics, the gut microbiome, genomics, neurology). Despite several decades of research, there are no established ME/CFS biomarkers available to diagnose and treat ME/CFS. Sharing data and integrating findings across these domains is essential to advance understanding of this complex disease by revealing diagnostic biomarkers and facilitating discovery of novel effective therapies. METHODS: The National Institutes of Health funded the development of a data sharing portal to support collaborative efforts among an initial group of three funded research centers. This was subsequently expanded to include the global ME/CFS research community. Using the open-source comprehensive knowledge archive network (CKAN) framework as the base, the ME/CFS Data Management and Coordinating Center developed an online portal with metadata collection, smart search capabilities, and domain-agnostic data integration to support data findability and reusability while reducing the barriers to sustainable data sharing. RESULTS: We designed the mapMECFS data portal to facilitate data sharing and integration by allowing ME/CFS researchers to browse, share, compare, and download molecular datasets from within one data repository. At the time of publication, mapMECFS contains data curated from public data repositories, peer-reviewed publications, and current ME/CFS Research Network members. CONCLUSIONS: mapMECFS is a disease-specific data portal to improve data sharing and collaboration among ME/CFS researchers around the world. mapMECFS is accessible to the broader research community with registration. Further development is ongoing to include novel systems biology and data integration methods.

Smoking and cessation-related attitudes among men who have sex with men in the country of Georgia.

Among men who have sex with men (MSM) in low- or middle-income countries, smoking and related factors have been understudied. We examined correlates of smoking status, level, and importance and confidence regarding quitting among 608 MSM in the country of Georgia recruited in June-September, 2016 (493 without HIV via peer referral in 3 Georgian cities; 115 with HIV via the National AIDS Center). Median age was 26 years, 78.6% reported current (past 30-day) alcohol use, and 22.4% reported past-year illicit drug use. Overall, 73.8% reported current smoking; of these, 87.1% smoked daily, mean cigarettes per day (cpd) was 19.8, 64.6% smoked ≤30 min of waking, and mean quitting importance and confidence were 6.8 and 6.4 (0 = not at all to 10 = extremely), respectively. Multivariable analyses indicated that current smoking correlated with past-month alcohol and past-year illicit drug use (p's < .001). Among smokers, cpd correlated with being older and smoking within 30 min of waking; greater quitting importance (≥7) correlated with higher education and no illicit substance use; and greater quitting confidence (≥7) was associated with fewer cpd, smoking ≤30 min of waking, and regional versus capital city residence. Given these findings, addressing tobacco and other substance use among MSM in Georgia is critical.

A Pilot Randomized Controlled Trial of Text Messaging to Increase Tobacco Treatment Reach in the Emergency Department.

INTRODUCTION: Automated text messaging programs have been studied as a treatment tool, but have not been studied as an outreach tool to increase the reach of smoking cessation treatment. AIMS AND METHODS: Two distinct text messaging programs were developed. One was aimed at connecting smokers to quitline phone counseling via text message (Text4Coach [T4C]) and the other was aimed at connecting smokers to a smoking cessation text messaging program (Text&Quit [T&Q]). Adult daily smokers with Medicaid insurance (N = 80) were recruited from the Emergency Department at an urban hospital and randomized to T4C or T&Q. The primary outcome was program reach. RESULTS: Outreach text messages were found to have moderately high uptake, with the majority of participants (63.8%) opting into their assigned tobacco treatment program and younger and female participants more likely to opt in (p < .01). Receipt of the treatment portion of the program differed among the programs with 67.5% of T&Q receiving the treatment program and 27.5% of T4C receiving the program (p < .001). Most participants across both groups replied to at least one message (71.3%) and very few unsubscribed from the service over the 3-week trial. The majority of participants reported overall satisfaction with their program (63.8%), found it helpful for quitting smoking (60.0%) and would recommend the program to a friend (62.5%). Overall, 11 (13.8%) participants reported being abstinent from smoking for the past 7 days at follow-up, with no differences between groups. CONCLUSIONS: Outreach text messages were found to have moderately high reach among Medicaid smokers. Larger trials are needed to evaluate the impact of such programs on helping low-income smokers quit. IMPLICATIONS: Automated text messaging programs have been tested as a treatment tool, but have not been tested as an outreach tool to increase the reach of smoking cessation treatment. This study tests a new way of conducting outreach to smokers in a health system through text messages. It tests the effect of outreach on (1) rates of opting in and (2) successful treatment delivery. Results may inform new models of providing outreach for tobacco treatment in health systems.

Pediatric Index of Mortality 3-An Evaluation of Function Among ICUs In South Africa.

OBJECTIVES: To evaluate the performance of the Pediatric Index of Mortality 3 as mortality risk assessment model. DESIGN: This prospective study included all admissions 30 days to 18 years old for 12 months during 2016 and 2017. Data gathered included the following: age and gender, diagnosis and reason for PICU admission, data specific for the Pediatric Index of Mortality 3 calculation, PICU outcomes (death or survival), and length of PICU stay. SETTING: Nine units that care for children within tertiary or quaternary academic hospitals in South Africa. PATIENTS: All admissions 30 days to 18 years old, excluding premature infants, children who died within 2 hours of admission, or children transferred to other PICUs, and those older than 18 years old. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: There were 3,681 admissions of which 2,253 (61.3%) were male. The median age was 18 months (interquartile range, 6-59.5 mo). There were 354 deaths (9.6%). The Pediatric Index of Mortality 3 predicted 277.47 deaths (7.5%). The overall standardized mortality ratio was 1.28. The area under the receiver operating characteristic curve was 0.81 (95% CI 0.79-0.83). The Hosmer-Lemeshow goodness-of-fit test statistic was 174.4 (p < 0.001). Standardized mortality ratio for all age groups was greater than 1. Standardized mortality ratio for diagnostic subgroups was mostly greater than 1 except for those whose reason for PICU admission was classified as accident, toxin and envenomation, and metabolic which had an standardized mortality ratio less than 1. There were similar proportions of respiratory patients, but significantly greater proportions of neurologic and cardiac (including postoperative) patients in the Pediatric Index of Mortality 3 derivation cohort than the South African cohort. In contrast, the South African cohort contained a significantly greater proportion of miscellaneous (including injury/accident victims) and postoperative noncardiac patients. CONCLUSIONS: The Pediatric Index of Mortality 3 discrimination between death and survival among South African units was good. Case-mix differences between these units and the Pediatric Index of Mortality 3 derivation cohort may partly explain the poor calibration. We need to recalibrate Pediatric Index of Mortality 3 to the local setting.

A physiology-based mathematical model for the selection of appropriate ventilator controls for lung and diaphragm protection.

Mechanical ventilation is used to sustain respiratory function in patients with acute respiratory failure. To aid clinicians in consistently selecting lung- and diaphragm-protective ventilation settings, a physiology-based decision support system is needed. To form the foundation of such a system, a comprehensive physiological model which captures the dynamics of ventilation has been developed. The Lung and Diaphragm Protective Ventilation (LDPV) model centers around respiratory drive and incorporates respiratory system mechanics, ventilator mechanics, and blood acid-base balance. The model uses patient-specific parameters as inputs and outputs predictions of a patient's transpulmonary and esophageal driving pressures (outputs most clinically relevant to lung and diaphragm safety), as well as their blood pH, under various ventilator and sedation conditions. Model simulations and global optimization techniques were used to evaluate and characterize the model. The LDPV model is demonstrated to describe a CO2 respiratory response that is comparable to what is found in literature. Sensitivity analysis of the model indicate that the ventilator and sedation settings incorporated in the model have a significant impact on the target output parameters. Finally, the model is seen to be able to provide robust predictions of esophageal pressure, transpulmonary pressure and blood pH for patient parameters with realistic variability. The LDPV model is a robust physiological model which produces outputs which directly target and reflect the risk of ventilator-induced lung and diaphragm injury. Ventilation and sedation parameters are seen to modulate the model outputs in accordance with what is currently known in literature.

Socio-demographic, behavioural and health-related characteristics associated with active commuting in a regional Australian state: Evidence from the 2016 Tasmanian Population Health Survey.

ISSUE ADDRESSED: Physical activity is lower and rates of preventable common diseases are higher in regional/rural than urban Australia. Active commuting (walking/bicycling to get from one place to another) may benefit health through increased physical activity, but most evidence of its correlates come from urban studies. This study aimed to investigate associations between active commuting, socio-demographic characteristics, behaviours, total physical activity and health in a regional/rural Australian state. METHODS: This study used data from the 2016 Tasmanian Population Health Survey, a representative cross-sectional self-report survey of 6,300 adults in Tasmania, Australia. Logistic regression modelling investigated associations between socio-demographic, behavioural and health characteristics and past week active commuting frequency. RESULTS: In multivariable models, being younger, having tertiary qualifications, living in a socio-economically advantaged area, being physically active, having a healthy body mass index and good/excellent self-rated health were associated with engaging in more active commuting. Inner regional dwellers were no more likely than outer regional dwellers to actively commute after covariate adjustment. CONCLUSION: Strategies to promote active commuting in regional/rural areas might consider targeting older adults, those less educated, those living in socio-economically disadvantaged areas, those less physically active, those with poorer health and those with higher body mass index. Research could further investigate why these groups appear to be less active for commuting purposes. SO WHAT?: Increasing physical activity and active commuting may help to reduce rates of preventable common diseases in regional/remote areas.

Effectiveness and Cost-Benefit of an Elementary School-Based Telehealth Program.

Utilization of telehealth in school-based health centers (SBHCs) is increasing rapidly during the COVID-19 pandemic. This study used a quasi-experimental design to evaluate the effect on school absences and cost-benefit of telehealth-exclusive SBHCs at 6 elementary schools from 2015-2017. The effect of telehealth on absences was estimated compared to students without telehealth using negative binomial regression controlling for absences and health suite visits in 2014 and sociodemographic characteristics. The sample included 7,164 observations from 4,203 students. Telehealth was associated with a 7.7% (p = 0.025; 95% CI: 1.0%, 14%) reduction in absences (0.60 days/year). The program cost $189,000/yr and an estimated total benefit of $384,995 (95% CI: $60,416; $687,479) and an annual net benefit of $195,873 (95% CI: -$128,706; $498,357). While this cost-benefit analysis is limited by a lack of data on total healthcare utilization, the use of telehealth-exclusive SBHCs can improve student health and attendance while delivering cost savings to society.

Simulation of Growth Trajectories of Childhood Obesity into Adulthood.

BACKGROUND: Although the current obesity epidemic has been well documented in children and adults, less is known about long-term risks of adult obesity for a given child at his or her present age and weight. We developed a simulation model to estimate the risk of adult obesity at the age of 35 years for the current population of children in the United States. METHODS: We pooled height and weight data from five nationally representative longitudinal studies totaling 176,720 observations from 41,567 children and adults. We simulated growth trajectories across the life course and adjusted for secular trends. We created 1000 virtual populations of 1 million children through the age of 19 years that were representative of the 2016 population of the United States and projected their trajectories in height and weight up to the age of 35 years. Severe obesity was defined as a body-mass index (BMI, the weight in kilograms divided by the square of the height in meters) of 35 or higher in adults and 120% or more of the 95th percentile in children. RESULTS: Given the current level of childhood obesity, the models predicted that a majority of today's children (57.3%; 95% uncertainly interval [UI], 55.2 to 60.0) will be obese at the age of 35 years, and roughly half of the projected prevalence will occur during childhood. Our simulations indicated that the relative risk of adult obesity increased with age and BMI, from 1.17 (95% UI, 1.09 to 1.29) for overweight 2-year-olds to 3.10 (95% UI, 2.43 to 3.65) for 19-year-olds with severe obesity. For children with severe obesity, the chance they will no longer be obese at the age of 35 years fell from 21.0% (95% UI, 7.3 to 47.3) at the age of 2 years to 6.1% (95% UI, 2.1 to 9.9) at the age of 19 years. CONCLUSIONS: On the basis of our simulation models, childhood obesity and overweight will continue to be a major health problem in the United States. Early development of obesity predicted obesity in adulthood, especially for children who were severely obese. (Funded by the JPB Foundation and others.).

Wait and snap: eastern snapping turtles (Chelydra serpentina) prey on migratory fish at road-stream crossing culverts.

There is growing evidence that culverts at road-stream crossings can increase fish density by reducing stream width and fish movement rates, making these passageways ideal predator ambush locations. In this study, we used a combination of videography and δ13C stable isotope analyses to investigate predator-prey interactions at a road-stream crossing culvert. Eastern snapping turtles (Chelydra serpentina) were found to regularly reside within the culvert to ambush migratory river herring (Alosa spp.). Resident fish species displayed avoidance of the snapping turtles, resulting in zero attempted attacks on these fish. In contrast, river herring did not display avoidance and were attacked by a snapping turtle on 79% of approaches with a 15% capture rate. Stable isotope analyses identified an apparent shift in turtle diet to consumption of river herring in turtles from culvert sites that was not observed in individuals from non-culvert sites. These findings suggest that anthropogenic barriers like culverts that are designed to allow passage may create predation opportunities by serving as a bottleneck to resident and migrant fish movement.