Sexual coordination in a whole-brain map of prairie vole pair bonding.

Sexual bonds are central to the social lives of many species, including humans, and monogamous prairie voles have become the predominant model for investigating such attachments. We developed an automated whole-brain mapping pipeline to identify brain circuits underlying pair-bonding behavior. We identified bonding-related c-Fos induction in 68 brain regions clustered in seven major brain-wide neuronal circuits. These circuits include known regulators of bonding, such as the bed nucleus of the stria terminalis, paraventricular hypothalamus, ventral pallidum, and prefrontal cortex. They also include brain regions previously unknown to shape bonding, such as ventromedial hypothalamus, medial preoptic area, and the medial amygdala, but that play essential roles in bonding-relevant processes, such as sexual behavior, social reward, and territorial aggression. Contrary to some hypotheses, we found that circuits active during mating and bonding were largely sexually monomorphic. Moreover, c-Fos induction across regions was strikingly consistent between members of a pair, with activity best predicted by rates of ejaculation. A novel cluster of regions centered in the amygdala remained coordinated after bonds had formed, suggesting novel substrates for bond maintenance. Our tools and results provide an unprecedented resource for elucidating the networks that translate sexual experience into an enduring bond.

Females counter-sing, but response to male song differs by sex in Alston's singing mouse.

Vocal display behaviours are common throughout the animal kingdom, play important roles in both courtship and aggression, and are frequent subjects of behavioural research. Although females of many species vocalize, an overwhelming fraction of behavioural research has focused on male display. We investigated vocal display behaviours in female singing mice (Scotinomys teguina), small muroid rodents in which both sexes produce songs consisting of trills of rapid, downward frequency sweeps. Previous research established that male singing mice increase song production and engage in precisely timed counter-singing behaviour in response to playback of conspecific male song. We tested whether female singing mice also increased their rate of singing in response to playback of male song, whether they counter-sing, and whether there are sexual dimorphisms in song effort. Our results demonstrate that much like males, female singing mice increase their song effort and counter-sing in response to playback of male song; however, females sing fewer and shorter songs compared to males. This study further informs the understanding of female vocal behaviour and establishes the singing mouse as a valuable model for investigating female vocal display.

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.

Sexual coordination in a whole-brain map of prairie vole pair bonding.

Sexual bonds are central to the social lives of many species, including humans, and monogamous prairie voles have become the predominant model for investigating such attachments. We developed an automated whole-brain mapping pipeline to identify brain circuits underlying pair-bonding behavior. We identified bonding-related c-Fos induction in 68 brain regions clustered in seven major brain-wide neuronal circuits. These circuits include known regulators of bonding, such as the bed nucleus of the stria terminalis, paraventricular hypothalamus, ventral pallidum, and prefrontal cortex. They also include brain regions previously unknown to shape bonding, such as ventromedial hypothalamus, medial preoptic area and the medial amygdala, but that play essential roles in bonding-relevant processes, such as sexual behavior, social reward and territorial aggression. Contrary to some hypotheses, we found that circuits active during mating and bonding were largely sexually monomorphic. Moreover, c-Fos induction across regions was strikingly consistent between members of a pair, with activity best predicted by rates of ejaculation. A novel cluster of regions centered in the amygdala remained coordinated after bonds had formed, suggesting novel substrates for bond maintenance. Our tools and results provide an unprecedented resource for elucidating the networks that translate sexual experience into an enduring bond.

Mapping the vocal circuitry of Alston's singing mouse with pseudorabies virus.

Vocalizations are often elaborate, rhythmically structured behaviors. Vocal motor patterns require close coordination of neural circuits governing the muscles of the larynx, jaw, and respiratory system. In the elaborate vocalization of Alston's singing mouse (Scotinomys teguina) each note of its rapid, frequency-modulated trill is accompanied by equally rapid modulation of breath and gape. To elucidate the neural circuitry underlying this behavior, we introduced the polysynaptic retrograde neuronal tracer pseudorabies virus (PRV) into the cricothyroid and digastricus muscles, which control frequency modulation and jaw opening, respectively. Each virus singly labels ipsilateral motoneurons (nucleus ambiguus for cricothyroid, and motor trigeminal nucleus for digastricus). We find that the two isogenic viruses heavily and bilaterally colabel neurons in the gigantocellular reticular formation, a putative central pattern generator. The viruses also show strong colabeling in compartments of the midbrain including the ventrolateral periaqueductal gray and the parabrachial nucleus, two structures strongly implicated in vocalizations. In the forebrain, regions important to social cognition and energy balance both exhibit extensive colabeling. This includes the paraventricular and arcuate nuclei of the hypothalamus, the lateral hypothalamus, preoptic area, extended amygdala, central amygdala, and the bed nucleus of the stria terminalis. Finally, we find doubly labeled neurons in M1 motor cortex previously described as laryngeal, as well as in the prelimbic cortex, which indicate these cortical regions play a role in vocal production. The progress of both viruses is broadly consistent with vertebrate-general patterns of vocal circuitry, as well as with circuit models derived from primate literature.

Individual differences in social attachment: A multi-disciplinary perspective.

Social behavior varies across both individuals and species. Research to explain this variation falls under the purview of multiple disciplines, each with its own theoretical and empirical traditions. Integration of these disciplinary traditions is key to developing a holistic perspective. Here, we review research on the biology of social attachment, a phenomena in which individuals develop strong affective connections to one another. We provide a historical overview of research on social attachment from psychological, ethological and neurobiological perspectives. As a case study, we describe work on pair-bonding in prairie voles, a socially monogamous rodent. This specific topic takes advantage of many biological perspectives and techniques to explain social bonds. Lastly, we conclude with an overview of multi-dimensional conceptual frameworks that can be used to explain social phenomena, and we propose a new framework for research on individual variation in attachment behavior. These conceptual frameworks originate from philosophy, physics, ethology, cognitive science and neuroscience. The application and synthesis of such frameworks offers a rich opportunity to advance understanding of social behavior and its mechanisms.

Reduced Mortality With Ondansetron Use in SARS-CoV-2-Infected Inpatients.

BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic has led to a surge in clinical trials evaluating investigational and approved drugs. Retrospective analysis of drugs taken by COVID-19 inpatients provides key information on drugs associated with better or worse outcomes. METHODS: We conducted a retrospective cohort study of 10 741 patients testing positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection within 3 days of admission to compare risk of 30-day all-cause mortality in patients receiving ondansetron using multivariate Cox proportional hazard models. All-cause mortality, length of hospital stay, adverse events such as ischemic cerebral infarction, and subsequent positive COVID-19 tests were measured. RESULTS: Administration of ≥8 mg of ondansetron within 48 hours of admission was correlated with an adjusted hazard ratio for 30-day all-cause mortality of 0.55 (95% CI, 0.42-0.70; P < .001) and 0.52 (95% CI, 0.31-0.87; P = .012) for all and intensive care unit-admitted patients, respectively. Decreased lengths of stay (9.2 vs 11.6; P < .001), frequencies of subsequent positive SARS-CoV-2 tests (53.6% vs 75.0%; P = .01), and long-term risks of ischemic cerebral ischemia (3.2% vs 6.1%; P < .001) were also noted. CONCLUSIONS: If confirmed by prospective clinical trials, our results suggest that ondansetron, a safe, widely available drug, could be used to decrease morbidity and mortality in at-risk populations.

Comparative neurotranscriptomics reveal widespread species differences associated with bonding.

BACKGROUND: Pair bonding with a reproductive partner is rare among mammals but is an important feature of human social behavior. Decades of research on monogamous prairie voles (Microtus ochrogaster), along with comparative studies using the related non-bonding meadow vole (M. pennsylvanicus), have revealed many of the neural and molecular mechanisms necessary for pair-bond formation in that species. However, these studies have largely focused on just a few neuromodulatory systems. To test the hypothesis that neural gene expression differences underlie differential capacities to bond, we performed RNA-sequencing on tissue from three brain regions important for bonding and other social behaviors across bond-forming prairie voles and non-bonding meadow voles. We examined gene expression in the amygdala, hypothalamus, and combined ventral pallidum/nucleus accumbens in virgins and at three time points after mating to understand species differences in gene expression at baseline, in response to mating, and during bond formation. RESULTS: We first identified species and brain region as the factors most strongly associated with gene expression in our samples. Next, we found gene categories related to cell structure, translation, and metabolism that differed in expression across species in virgins, as well as categories associated with cell structure, synaptic and neuroendocrine signaling, and transcription and translation that varied among the focal regions in our study. Additionally, we identified genes that were differentially expressed across species after mating in each of our regions of interest. These include genes involved in regulating transcription, neuron structure, and synaptic plasticity. Finally, we identified modules of co-regulated genes that were strongly correlated with brain region in both species, and modules that were correlated with post-mating time points in prairie voles but not meadow voles. CONCLUSIONS: These results reinforce the importance of pre-mating differences that confer the ability to form pair bonds in prairie voles but not promiscuous species such as meadow voles. Gene ontology analysis supports the hypothesis that pair-bond formation involves transcriptional regulation, and changes in neuronal structure. Together, our results expand knowledge of the genes involved in the pair bonding process and open new avenues of research in the molecular mechanisms of bond formation.

Conservation and dimorphism in androgen receptor distribution in Alston's singing mouse (Scotinomys teguina).

Because of their roles in courtship and intrasexual competition, sexual displays are often sexually dimorphic, but we know little about the mechanisms that produce such dimorphism. Among mammals, one example is the vocalization of Alston's singing mouse (Scotinomys teguina), which consists of a series of rapidly repeated, frequency-modulated notes. The rate and duration of songs is sexually dimorphic and androgen responsive. To understand the neuronal mechanisms underlying this sexual dimorphism, we map the sites of androgen sensitivity throughout the brain, focusing analysis along a pathway that spans from limbic structures to vocal motor regions. We find widespread expression of AR immunoreactivity (AR-ir) throughout limbic structures important for social behavior and vocalization, including the lateral septum, extended amygdala, preoptic area and hypothalamus. We also find extensive AR staining along previously documented vocal motor pathways, including the periaqueductal gray, parabrachial nucleus, and nucleus ambiguus, the last of which innervates intrinsic laryngeal muscles. Lastly, AR-ir is also evident in sensory areas such as the medial geniculate, inferior, and superior colliculi. A quantitative analysis revealed that males exhibited more AR-ir than females, a pattern that was most pronounced in the hypothalamus. Despite the elaboration of vocalization in singing mice, comparison with prior literature suggests that the broad pattern of AR-ir may be conserved across a wide range of rodents. Together these data identify brain nuclei well positioned to shape the sexually dimorphic vocalization of S. teguina and suggest that such androgen modulation of vocalization is evolutionary conserved among rodents.

A Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Prediction Model From Standard Laboratory Tests.

BACKGROUND: With the limited availability of testing for the presence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus and concerns surrounding the accuracy of existing methods, other means of identifying patients are urgently needed. Previous studies showing a correlation between certain laboratory tests and diagnosis suggest an alternative method based on an ensemble of tests. METHODS: We have trained a machine learning model to analyze the correlation between SARS-CoV-2 test results and 20 routine laboratory tests collected within a 2-day period around the SARS-CoV-2 test date. We used the model to compare SARS-CoV-2 positive and negative patients. RESULTS: In a cohort of 75 991 veteran inpatients and outpatients who tested for SARS-CoV-2 in the months of March through July 2020, 7335 of whom were positive by reverse transcription polymerase chain reaction (RT-PCR) or antigen testing, and who had at least 15 of 20 lab results within the window period, our model predicted the results of the SARS-CoV-2 test with a specificity of 86.8%, a sensitivity of 82.4%, and an overall accuracy of 86.4% (with a 95% confidence interval of [86.0%, 86.9%]). CONCLUSIONS: Although molecular-based and antibody tests remain the reference standard method for confirming a SARS-CoV-2 diagnosis, their clinical sensitivity is not well known. The model described herein may provide a complementary method of determining SARS-CoV-2 infection status, based on a fully independent set of indicators, that can help confirm results from other tests as well as identify positive cases missed by molecular testing.

A comparative characterization of laryngeal anatomy in the singing mouse.

Sexual displays are some of the most dramatic and varied behaviors that have been documented. The elaboration of such behaviors often relies on the modification of existing morphology. To understand how display elaboration arises, we analyzed the laryngeal anatomy of three species of mice that vary in the presence and complexity of their vocal displays. Mice and rats have a specialized larynx that enables them to produce both low-frequency "audible" sounds, perhaps using vocal fold vibration, as well as distinct mechanisms that are thought to enable higher frequency sounds, such as vocal membrane vibration and intralaryngeal whistles. These mechanisms rely on different structures within the larynx. Using histology, we characterized laryngeal anatomy in Alston's singing mouse (Scotinomys teguina), the northern pygmy mouse (Baiomys taylori), and the laboratory mouse (Mus musculus), which produce different types of vocalizations. We found evidence of a vocal membrane in all species, as well as species differences in vocal fold and ventral pouch size. Presence of a vocal membrane in these three species, which are not known to use vocal membrane vibration, suggests that this structure may be widespread among muroid rodents. An expanded ventral pouch in singing and pygmy mice suggests that these mice may use an intralaryngeal whistle to produce their advertisement songs, and that an expanded ventral pouch may enable lower frequencies than laboratory mouse whistle-produced sounds. Variation in the laryngeal anatomy of rodents fits into a larger pattern across terrestrial vertebrates, where the development and modification of vocal membranes and pouches, or air sacs, are common mechanisms by which vocalizations diversify. Understanding variation in the functional anatomy of relevant organs is the first step in understanding how morphological changes enable novel displays.

Singing mice.

A Quick guide to singing mice.

Motor cortical control of vocal interaction in neotropical singing mice.

Like many adaptive behaviors, acoustic communication often requires rapid modification of motor output in response to sensory cues. However, little is known about the sensorimotor transformations that underlie such complex natural behaviors. In this study, we examine vocal exchanges in Alston's singing mouse (Scotinomys teguina). We find that males modify singing behavior during social interactions on a subsecond time course that resembles both traditional sensorimotor tasks and conversational speech. We identify an orofacial motor cortical region and, via a series of perturbation experiments, demonstrate a hierarchical control of vocal production, with the motor cortex influencing the pacing of singing behavior on a moment-by-moment basis, enabling precise vocal interactions. These results suggest a systems-level framework for understanding the sensorimotor transformations that underlie natural social interactions.

Conserved transcriptomic profiles underpin monogamy across vertebrates.

Social monogamy, typically characterized by the formation of a pair bond, increased territorial defense, and often biparental care, has independently evolved multiple times in animals. Despite the independent evolutionary origins of monogamous mating systems, several homologous brain regions and neuropeptides and their receptors have been shown to play a conserved role in regulating social affiliation and parental care, but little is known about the neuromolecular mechanisms underlying monogamy on a genomic scale. Here, we compare neural transcriptomes of reproductive males in monogamous and nonmonogamous species pairs of Peromyscus mice, Microtus voles, parid songbirds, dendrobatid frogs, and Xenotilapia species of cichlid fishes. We find that, while evolutionary divergence time between species or clades did not explain gene expression similarity, characteristics of the mating system correlated with neural gene expression patterns, and neural gene expression varied concordantly across vertebrates when species transition to monogamy. Our study provides evidence of a universal transcriptomic mechanism underlying the evolution of monogamy in vertebrates.

Adiposity signals predict vocal effort in Alston's singing mice.

Advertisement displays often seem extravagant and expensive, and are thought to depend on the body condition of a signaller. Nevertheless, we know little about how signallers adjust effort based on condition, and few studies find a strong relationship between natural variation in condition and display. To examine the relationship between body condition and signal elaboration more fully, we characterized physiological condition and acoustic displays in a wild rodent with elaborate vocalizations, Alston's singing mouse, Scotinomys teguina We found two major axes of variation in condition-one defined by short-term fluctuations in caloric nutrients, and a second by longer-term variation in adiposity. Among acoustic parameters, song effort was characterized by high rates of display and longer songs. Song effort was highly correlated with measures of adiposity. We found that leptin was a particularly strong predictor of display effort. Leptin is known to influence investment in other costly traits, such as immune function and reproduction. Plasma hormone levels convey somatic state to a variety of tissues, and may govern trait investment across vertebrates. Such measures offer new insights into how animals translate body condition into behavioural and life-history decisions.

Genomic tools for behavioural ecologists to understand repeatable individual differences in behaviour.

Behaviour is a key interface between an animal's genome and its environment. Repeatable individual differences in behaviour have been extensively documented in animals, but the molecular underpinnings of behavioural variation among individuals within natural populations remain largely unknown. Here, we offer a critical review of when molecular techniques may yield new insights, and we provide specific guidance on how and whether the latest tools available are appropriate given different resources, system and organismal constraints, and experimental designs. Integrating molecular genetic techniques with other strategies to study the proximal causes of behaviour provides opportunities to expand rapidly into new avenues of exploration. Such endeavours will enable us to better understand how repeatable individual differences in behaviour have evolved, how they are expressed and how they can be maintained within natural populations of animals.

Complex selection on a regulator of social cognition: Evidence of balancing selection, regulatory interactions and population differentiation in the prairie vole Avpr1a locus.

Adaptive variation in social behaviour depends upon standing genetic variation, but we know little about how evolutionary forces shape genetic diversity relevant to brain and behaviour. In prairie voles (Microtus ochrogaster), variants at the Avpr1a locus predict expression of the vasopressin 1a receptor in the retrosplenial cortex (RSC), a brain region that mediates spatial and contextual memory; cortical V1aR abundance in turn predicts diversity in space use and sexual fidelity in the field. To examine the potential contributions of adaptive and neutral forces to variation at the Avpr1a locus, we explore sequence diversity at the Avpr1a locus and throughout the genome in two populations of wild prairie voles. First, we refine results demonstrating balancing selection at the locus by comparing the frequency spectrum of variants at the locus to a random sample of the genome. Next, we find that the four single nucleotide polymorphisms that predict high V1aR expression in the RSC are in stronger linkage disequilibrium than expected by chance despite high recombination among intervening variants, suggesting that epistatic selection maintains their association. Analysis of population structure and a haplotype network for two populations revealed that this excessive LD was unlikely to be due to admixture alone. Furthermore, the two populations differed considerably in the region shown to be a regulator of V1aR expression despite the extremely low levels of genomewide genetic differentiation. Together, our data suggest that complex selection on Avpr1a locus favours specific combinations of regulatory polymorphisms, maintains the resulting alleles at population-specific frequencies, and may contribute to unique patterns of spatial cognition and sexual fidelity among populations.