Pebble to the Metal: A Boulder Approach to Enrichment for Danio rerio.

Zebrafish are an established and widely used animal model, yet there is limited understanding of their welfare needs. Despite an increasing number of studies on zebrafish enrichment, in-tank environmental enrichment remains unpopular among researchers. This is due to perceived concerns over health/hygiene when it comes to introducing enrichment into the tank, although actual evidence for this is sparse. To accommodate this belief, regardless of veracity, we tested the potential benefits of enrichments presented outside the tank. Thus, we investigated the preferences and physiological stress of zebrafish with pictures of pebbles placed underneath the tank. We hypothesized that zebrafish would show a preference for enriched environments and have lower stress levels than barren housed zebrafish. In our first experiment, we housed zebrafish in a standard rack system and recorded their preference for visual access to a pebble picture, with two positive controls: visual access to conspecifics, and group housing. Using a crossover repeated-measures factorial design, we tested if the preference for visual access to pebbles was as strong as the preference for social contact. Zebrafish showed a strong preference for visual access to pebbles, equivalent to that for conspecifics. Then, in a second experiment, tank water cortisol was measured to assess chronic stress levels of zebrafish housed with or without a pebble picture under their tank, with group housing as a positive control. Cortisol levels were significantly reduced in zebrafish housed with pebble pictures, as were cortisol levels in group housed zebrafish. In fact, single housed zebrafish with pebble pictures showed the same cortisol levels as group housed zebrafish without pebble pictures. Thus, the use of an under-tank pebble picture was as beneficial as being group housed, effectively compensating for the stress of single housing. Pebble picture enrichment had an additive effect with group housing, where group housed zebrafish with pebble pictures had the lowest cortisol levels of any treatment group.

Chronic Adaptations in the Dorsal Horn Following a Cervical Spinal Cord Injury in Primates.

Spinal cord injury (SCI) is devastating, with limited treatment options and variable outcomes. Most in vivo SCI research has focused on the acute and early post-injury periods, and the promotion of axonal growth, so little is understood about the clinically stable chronic state, axonal growth over time, and what plasticity endures. Here, we followed animals into the chronic phase following SCI, to address this gap. Male macaques received targeted deafferentation, affecting three digits of one hand, and were divided into short (4-6 months) or long-term (11-12 months) groups, based on post-injury survival times. Monkeys were assessed behaviorally, where possible, and all exhibited an initial post-injury deficit in manual dexterity, with gradual functional recovery over 2 months. We previously reported extensive sprouting of somatosensory corticospinal (S1 CST) fibers in the dorsal horn in the first five post-injury months. Here, we show that by 1 year, the S1 CST sprouting is pruned, with the terminal territory resembling control animals. This was reflected in the number of putatively "functional" synapses observed, which increased over the first 4-5 months, and then returned to baseline by 1 year. Microglia density also increased in the affected dorsal horn at 4-6 months and then decreased, but did not return to baseline by 1 year, suggesting refinement continues beyond this time. Overall, there is a long period of reorganization and consolidation of adaptive circuitry in the dorsal horn, extending well beyond the initial behavioral recovery. This provides a potential window to target therapeutic opportunities during the chronic phase.

Naturally occurring low sociality in female rhesus monkeys: A tractable model for autism or not?

BACKGROUND: Autism spectrum disorder (ASD) is characterized by persistent social interaction impairments and is male-biased in prevalence. We have established naturally occurring low sociality in male rhesus monkeys as a model for the social features of ASD. Low-social male monkeys exhibit reduced social interactions and increased autistic-like trait burden, with both measures highly correlated and strongly linked to low cerebrospinal fluid (CSF) arginine vasopressin (AVP) concentration. Little is known, however, about the behavioral and neurochemical profiles of female rhesus monkeys, and whether low sociality in females is a tractable model for ASD. METHODS: Social behavior assessments (ethological observations; a reverse-translated autistic trait measurement scale, the macaque Social Responsiveness Scale-Revised [mSRS-R]) were completed on N = 88 outdoor-housed female rhesus monkeys during the non-breeding season. CSF and blood samples were collected from a subset of N = 16 monkeys across the frequency distribution of non-social behavior, and AVP and oxytocin (OXT) concentrations were quantified. Data were analyzed using general linear models. RESULTS: Non-social behavior frequency and mSRS-R scores were continuously distributed across the general female monkey population, as previously found for male monkeys. However, dominance rank significantly predicted mSRS-R scores in females, with higher-ranking individuals showing fewer autistic-like traits, a relationship not previously observed in males from this colony. Females differed from males in several other respects: Social behavior frequencies were unrelated to mSRS-R scores, and AVP concentration was unrelated to any social behavior measure. Blood and CSF concentrations of AVP were positively correlated in females; no significant relationship involving any OXT measure was found. LIMITATIONS: This study sample was small, and did not consider genetic, environmental, or other neurochemical measures that may be related to female mSRS-R scores. CONCLUSIONS: Dominance rank is the most significant predictor of autistic-like traits in female rhesus monkeys, and CSF neuropeptide concentrations are unrelated to measures of female social functioning (in contrast to prior CSF AVP findings in male rhesus monkeys and male and female autistic children). Although preliminary, this evidence suggests that the strong matrilineal organization of this species may limit the usefulness of low sociality in female rhesus monkeys as a tractable model for ASD.

Rhesus macaque social functioning is paternally, but not maternally, inherited by sons: potential implications for autism.

BACKGROUND: Quantitative autistic traits are common, heritable, and continuously distributed across the general human population. Patterns of autistic traits within families suggest that more complex mechanisms than simple Mendelian inheritance-in particular, parent of origin effects-may be involved. The ideal strategy for ascertaining parent of origin effects is by half-sibling analysis, where half-siblings share one, but not both, parents and each individual belongs to a unique combination of paternal and maternal half-siblings. While this family structure is rare in humans, many of our primate relatives, including rhesus macaques, have promiscuous breeding systems that consistently produce paternal and maternal half-siblings for a given index animal. Rhesus macaques, like humans, also exhibit pronounced variation in social functioning. METHODS: Here we assessed differential paternal versus maternal inheritance of social functioning in male rhesus macaque offspring (N = 407) using ethological observations and ratings on a reverse-translated quantitative autistic trait measurement scale. Restricted Maximum Likelihood mixed models with unbounded variance estimates were used to estimate the variance components needed to calculate the genetic contribution of parents as the proportion of phenotypic variance (σ2P) between sons that could uniquely be attributed to their shared genetics (σ2g), expressed as σ2g/σ2P (or the proportion of phenotypic variance attributable to genetic variance), as well as narrow sense heritability (h2). RESULTS: Genetic contributions and heritability estimates were strong and highly significant for sons who shared a father but weak and non-significant for sons who shared a mother. Importantly, these findings were detected using the same scores from the same sons in the same analysis, confirmed when paternal and maternal half-siblings were analyzed separately, and observed with two methodologically distinct behavioral measures. Finally, genetic contributions were similar for full-siblings versus half-siblings that shared only a father, further supporting a selective paternal inheritance effect. LIMITATIONS: These data are correlational by nature. A larger sample that includes female subjects, enables deeper pedigree assessments, and supports molecular genetic analyses is warranted. CONCLUSIONS: Rhesus macaque social functioning may be paternally, but not maternally, inherited by sons. With continued investigation, this approach may yield important insights into sex differences in autism's genetic liability.

A Cross-sectional Survey on Rodent Environmental Health Monitoring Practices: Benchmarking, Associations, and Barriers.

Tens of thousands of rodents are used each year in Rodent Health Monitoring programs. However, Environment Health Monitoring (EHM) could replace sentinel rodent use while maintaining or even improving diagnostic quality. Despite its advantages, widespread implementation of EHM appears to be relatively low. To better understand EHM's prevalence and factors influencing its use, we surveyed research animal professionals. Our hypotheses were (1) EHM prevalence would be low and (2) EHM use would be associated with beliefs and knowledge about EHM. Participants were recruited via online promotion. A total of 158 individuals completed a mixed-methods survey about current practices, beliefs, and knowledge about EHM. Qualitative data were coded using thematic analysis and analyzed using generalized linear models. Results showed that current EHM implementation was low; only 11% of institutions used EHM exclusively. Across the 111 institutions surveyed, over 20,000 soiled bedding sentinels were used each year. However, most participants believed EHM to be advantageous in replacing sentinel animals (78% of participants). Some participants believed EHM could save time (31%), cost less (27%), and be highly accurate (15%). Conversely, some participants believed EHM would be difficult to use due to their current caging type (40%), higher costs (21%), lower accuracy (16%), and personnel attitudes/expertise (14%). Overall, respondents with higher planned EHM use also had more positive attitudes, norms, and control of EHM. We also identified several factors that could promote the implementation of EHM. Communication efforts should emphasize that EHM is compatible with various types of caging, can provide cost savings, has high accuracy, and is consistent with the 3Rs as a replacement. Efforts should also focus on improving attitudes, encouraging peers, and providing resources to facilitate implementation. Implementation in just the surveyed institutions could eliminate the need for well over 20,000 rodents each year, consistent with 3Rs goals.

Rhesus monkey sociality is stable across time and linked to variation in the initiation but not receipt of prosocial behavior.

Rhesus monkeys and humans are highly social primates, yet both species exhibit pronounced variation in social functioning, spanning a spectrum of sociality. Naturally occurring low sociality in rhesus monkeys may be a promising construct by which to model social impairments relevant to human autism spectrum disorder (ASD), particularly if low sociality is found to be stable across time and associated with diminished social motivation. Thus, to better characterize variation in sociality and social communication profiles, we performed quantitative social behavior assessments on N = 95 male rhesus macaques (Macaca mulatta) housed in large, outdoor groups. In Study 1, we determined the social classification of our subjects by rank-ordering their total frequency of nonsocial behavior. Monkeys with the greatest frequency of nonsocial behavior were classified as low-social (n = 20) and monkeys with the lowest frequency of nonsocial behavior were classified as high-social (n = 21). To assess group differences in social communication profiles, in Study 2, we quantified the rates of transient social communication signals, and whether these social signals were initiated by or directed towards the focal subject. Finally, in Study 3, we assessed the within-individual stability of sociality in a subset of monkeys (n = 11 low-social, n = 11 high-social) two years following our initial observations. Nonsocial behavior frequency significantly correlated across the two timepoints (Studies 1 and 3). Likewise, low-social versus high-social classification accurately predicted classification two years later. Low-social monkeys initiated less prosocial behavior than high-social monkeys, but groups did not differ in receipt of prosocial behavior, nor did they differ in threat behavior. These findings indicate that sociality is a stable, trait-like characteristic and that low sociality is linked to diminished initiation of prosocial behavior in rhesus macaques. This evidence also suggests that low sociality may be a useful construct for gaining mechanistic insight into the social motivational deficits often observed in people with ASD.

Small sensory spinal lesions that affect hand function in monkeys greatly alter primary afferent and motor neuron connections in the cord.

Small sensory spinal injuries induce plasticity across the neuraxis, but little is understood about their effect on segmental connections or motor neuron (MN) function. Here, we begin to address this at two levels. First, we compared afferent input distributions from the skin and muscles of the digits with corresponding MN pools to determine their spatial relationship, in both the normal state and 4-6 months after a unilateral dorsal root/dorsal column lesion (DRL/DCL), affecting digits 1-3. Second, we looked at specific changes to MN inputs and membrane properties that likely impact functional recovery. Monkeys received a targeted unilateral DRL/DCL, and 4-6 months later, cholera toxin subunit B (CT-B) was injected bilaterally into either the distal pads of digits 1-3, or related intrinsic hand muscles, to label inputs to the cord, and corresponding MNs. In controls (unlesioned side), cutaneous and proprioceptive afferents from digits 1-3 showed different distribution patterns but similar rostrocaudal spread within the dorsal horn from C1 to T2. In contrast, MNs were distributed across just two segments (C7-8). Following the lesion, sensory inputs were significantly diminished across all 10 segments, though this did not alter MN distributions. Afferent and monoamine inputs, as well as KCC2 cotransporters, were also significantly altered on the cell membrane of CT-B labeled MNs postlesion. In contrast, inhibitory neurotransmission and perineuronal net integrity were not altered at this prechronic timepoint.  Our findings indicate that even a small sensory injury can significantly impact sensory and motor spinal neurons and provide new insight into the complex process of recovery.

Propofol Immersion As a Euthanasia Method for Adult Zebrafish (Danio Rerio).

The exponential rise of the zebrafish (Danio rerio) as a model organism in biomedical research has far outstripped our un- derstanding of basic husbandry and welfare for this species. As a case in point, here we investigate the efficacy and welfare impact of different euthanasia methods for zebrafish. Not only is a humane death central to welfare and the 3Rs, but stress during euthanasia can change scientific outcomes. However, the most frequently used methods of euthanasia have multiple shortcomings with regard to animal welfare and human safety. In this study, we propose the use of propofol for immersion euthanasia of adult zebrafish. Propofol has been known to rapidly induce anesthesia in many species, including zebrafish, but its efficacy as a euthanasia agent for zebrafish has not fully been explored. In this study, adult zebrafish were euthanized by immersion on one of 5 different preparations: ice bath, 250 ppm MS222, 600 ppm lidocaine hydrochloride, 100 ppm propofol, or 150 ppm propofol for 20 or 30 min. Display of aversive behaviors, time to loss of righting reflex, time to cessation of opercular movement, and time to recovery after transfer to clean tank water were assessed and recorded. Propofol at both concentrations induced loss of righting reflex and loss of opercular movement more quickly than did MS222 or lidocaine hydrochloride and caused no display of aversive behaviors as seen with ice bath or lidocaine exposure. However, fish exposed to propofol at either concentration for 20 min sometimes recovered, whereas a 30-min exposure was sufficient for euthanasia of all fish tested. These findings suggest that exposure to propofol for a duration of at least 30 min quickly and effectively euthanizes adult zebrafish without compromising end-of-life welfare.

Oxytocin and the social facilitation of placebo effects.

Significant clinical improvement is often observed in patients who receive placebo treatment in randomized double-blind placebo-controlled trials. While a proportion of this "improvement" reflects experimental design limitations (e.g., reliance on subjective outcomes, unbalanced groups, reporting biases), some of it reflects genuine improvement corroborated by physiological change. Converging evidence across diverse medical conditions suggests that clinically-relevant benefits from placebo treatment are associated with the activation of brain reward circuits. In parallel, evidence has accumulated showing that such benefits are facilitated by clinicians that demonstrate warmth and proficiency during interactions with patients. Here, we integrate research on these neural and social aspects of placebo effects with evidence linking oxytocin and social reward to advance a neurobiological account for the social facilitation of placebo effects. This account frames oxytocin as a key mediator of treatment success across a wide-spectrum of interventions that increase social connectedness, thereby providing a biological basis for assessing this fundamental non-specific element of medical care.

Behavioral recovery after a spinal deafferentation injury in monkeys does not correlate with extent of corticospinal sprouting.

A long held view in the spinal cord injury field is that corticospinal terminal sprouting is needed for new connections to form, that then mediate behavioral recovery. This makes sense, but tells us little about the relationship between corticospinal sprouting extent and recovery potential. The inference has been that more extensive axonal sprouting predicts greater recovery, though there is little evidence to support this. Here we addressed this by comparing behavioral data from monkeys that had received one of two established deafferentation spinal injury models in monkeys (Darian-Smith et al., 2014, Fisher et al., 2019, 2020). Both injuries cut similar afferent pools supplying the thumb, index and middle fingers of one hand but each resulted in a very different corticospinal tract (CST) sprouting response. Following a cervical dorsal root lesion, the somatosensory CST retracted significantly, while the motor CST stayed largely intact. In contrast, when a dorsal column lesion was combined with the DRL, somatosensory and motor CSTs sprouted dramatically within the cervical cord. How these two responses relate to the behavioral outcome was not clear. Here we analyzed the behavioral outcome for the two lesions, and provide a clear example that sprouting extent does not track with behavioral recovery.

Autism-associated biomarkers: test-retest reliability and relationship to quantitative social trait variation in rhesus monkeys.

BACKGROUND: Rhesus monkeys (Macaca mulatta) exhibit pronounced individual differences in social traits as measured by the macaque Social Responsiveness Scale-Revised. The macaque Social Responsiveness Scale was previously adapted from the Social Responsiveness Scale, an instrument designed to assess social and autistic trait variation in humans. To better understand potential biological underpinnings of this behavioral variation, we evaluated the trait-like consistency of several biological measures previously implicated in autism (e.g., arginine vasopressin, oxytocin, and their receptors, as well as ERK1/2, PTEN, and AKT(1-3) from the RAS-MAPK and PI3K-AKT pathways). We also tested which biological measures predicted macaque Social Responsiveness Scale-Revised scores. METHODS: Cerebrospinal fluid and blood samples were collected from N = 76 male monkeys, which, as a sample, showed a continuous distribution on the macaque Social Responsiveness Scale-Revised. In a subset of these subjects (n = 43), samples were collected thrice over a 10-month period. The following statistical tests were used: "Case 2A" intra-class correlation coefficients of consistency, principal component analysis, and general linear modeling. RESULTS: All biological measures (except AKT) showed significant test-retest reliability within individuals across time points. We next performed principal component analysis on data from monkeys with complete biological measurement sets at the first time point (n = 57), to explore potential correlations between the reliable biological measures and their relationship to macaque Social Responsiveness Scale-Revised score; a three-component solution was found. Follow-up analyses revealed that cerebrospinal fluid arginine vasopressin concentration, but no other biological measure, robustly predicted individual differences in macaque Social Responsiveness Scale-Revised scores, such that monkeys with the lowest cerebrospinal fluid arginine vasopressin concentration exhibited the greatest social impairment. Finally, we confirmed that this result held in the larger study sample (in which cerebrospinal fluid arginine vasopressin values were available from n = 75 of the subjects). CONCLUSIONS: These findings indicate that cerebrospinal fluid arginine vasopressin concentration is a stable trait-like measure and that it is linked to quantitative social trait variation in male rhesus monkeys.

Full closed loop open-source algorithm performance comparison in pigs with diabetes.

Understanding how automated insulin delivery (AID) algorithm features impact glucose control under full closed loop delivery represents a critical step toward reducing patient burden by eliminating the need for carbohydrate entries at mealtimes. Here, we use a pig model of diabetes to compare AndroidAPS and Loop open-source AID systems without meal announcements. Overall time-in-range (70-180 mg/dl) for AndroidAPS was 58% ± 5%, while time-in-range for Loop was 35% ± 5%. The effect of the algorithms on time-in-range differed between meals and overnight. During the overnight monitoring period, pigs had an average time-in-range of 90% ± 7% when on AndroidAPS compared to 22% ± 8% on Loop. Time-in-hypoglycemia also differed significantly during the lunch meal, whereby pigs running AndroidAPS spent an average of 1.4% (+0.4/-0.8)% in hypoglycemia compared to 10% (+3/-6)% for those using Loop. As algorithm design for closed loop systems continues to develop, the strategies employed in the OpenAPS algorithm (known as oref1) as implemented in AndroidAPS for unannounced meals may result in a better overall control for full closed loop systems.

Assessment of medical morbidities in a rhesus monkey model of naturally occurring low sociality.

People with autism spectrum disorder (ASD) exhibit a variety of medical morbidities at significantly higher rates than the general population. Using an established monkey model of naturally occurring low sociality, we investigated whether low-social monkeys show an increased burden of medical morbidities compared to their high-social counterparts. We systematically reviewed the medical records of N = 152 (n = 73 low-social; n = 79 high-social) rhesus macaques (Macaca mulatta) to assess the number of traumatic injury, gastrointestinal, and inflammatory events, as well as the presence of rare medical conditions. Subjects' nonsocial scores, determined by the frequency they were observed in a nonsocial state (i.e., alone), and macaque Social Responsiveness Scale-Revised (mSRS-R) scores were also used to test whether individual differences in social functioning were related to medical morbidity burden. Medical morbidity type significantly differed by group, such that low-social monkeys incurred higher rates of traumatic injury compared to high-social monkeys. Nonsocial scores and mSRS-R scores also significantly and positively predicted traumatic injury rates, indicating that monkeys with the greatest social impairment were most impacted on this health measure. These findings from low-social monkeys are consistent with well-documented evidence that people with ASD incur a greater number of traumatic injuries and receive more peer bullying than their neurotypical peers, and add to growing evidence for the face validity of this primate model. LAY SUMMARY: People with autism exhibit multiple medical problems at higher rates than the general population. We conducted a comprehensive medical record review of monkeys that naturally exhibit differences in sociality and found that low-social monkeys are more susceptible to traumatic injuries than high-social monkeys. These results are consistent with reports that people with autism also incur greater traumatic injury and peer bullying and add to growing evidence for the validity of this monkey model.

Complex Interplay Between Cognitive Ability and Social Motivation in Predicting Social Skill: A Unique Role for Social Motivation in Children With Autism.

Impairment in social interaction is a core feature of autism spectrum disorder (ASD), but the factors which contribute to this social skill deficiency are poorly understood. Previous research has shown that cognitive ability can impact social skill development in ASD. Yet, children with ASD whose cognitive abilities are in the normal range nevertheless demonstrate deficits in social skill. More recently, the social motivation theory of ASD has emerged as a framework by which to understand how failure to seek social experiences may lead to social skill deficits. This study was designed to better understand the relationships between cognitive ability, social motivation, and social skill in a well-characterized cohort of children with ASD (n = 79), their unaffected siblings (n = 50), and unrelated neurotypical controls (n = 60). The following instruments were used: The Stanford-Binet intelligence quotient (IQ), the Social Responsiveness Scale's Social Motivation Subscale, and the Vineland Adaptive Behavior Scales' Socialization Standard Score. We found that lower cognitive ability contributed to diminished social skill, but did so universally in all children. In contrast, social motivation strongly predicted social skill only in children with ASD, such that those with the lowest social motivation exhibited the greatest social skill impairment. Notably, this relationship was observed across a large range of intellectual ability but was most pronounced in those with IQs ≥ 80. These findings establish a unique link between social motivation and social skill in ASD and support the hypothesis that low social motivation may impair social skill acquisition in this disorder, particularly in children without intellectual disability. LAY SUMMARY: The relationships between cognitive ability, social motivation, and social skill are poorly understood. Here we report that cognitive ability predicts social skill in all children, whereas social motivation predicts social skill only in children with autism. These results establish a unique link between social motivation and social skill in autism, and suggest that low social motivation may impair social skill acquisition in this disorder, particularly in those without intellectual disability.

Natural food intake patterns have little synchronizing effect on peripheral circadian clocks.

BACKGROUND: Circadian rhythms across mammalian tissues are coordinated by a master clock in the suprachiasmatic nucleus (SCN) that is principally entrained by light-dark cycles. Prior investigations have shown, however, that time-restricted feeding (TRF)-daily alternation of fasting and food availability-synchronizes peripheral clocks independent of the light-dark cycle and of the SCN. This has led to the idea that downstream peripheral clocks are entrained indirectly by food intake rhythms. However, TRF is not a normal eating pattern, and it imposes non-physiologic long fasts that rodents do not typically experience. Therefore, we tested whether normal feeding patterns can phase-shift or entrain peripheral tissues by measuring circadian rhythms of the liver, kidney, and submandibular gland in mPer2Luc mice under different food schedules. RESULTS: We employed home cage feeders to first measure ad libitum food intake and then to dispense 20-mg pellets on a schedule mimicking that pattern. In both conditions, PER2::LUC bioluminescence peaked during the night as expected. Surprisingly, shifting the scheduled feeding by 12 h advanced peripheral clocks by only 0-3 h, much less than predicted from TRF protocols. To isolate the effects of feeding from the light-dark cycle, clock phase was then measured in mice acclimated to scheduled feeding over the course of 3 months in constant darkness. In these conditions, peripheral clock phases were better predicted by the rest-activity cycle than by the food schedule, contrary to expectation based on TRF studies. At the end of both experiments, mice were exposed to a modified TRF with food provided in eight equally sized meals over 12 h. In the light-dark cycle, this advanced the phase of the liver and kidney, though less so than in TRF with ad libitum access; in darkness, this entrained the liver and kidney but had little effect on the submandibular gland or the rest-activity cycle. CONCLUSIONS: These data suggest that natural feeding patterns can only weakly affect circadian clocks. Instead, in normally feeding mice, the central pacemaker in the brain may set the phase of peripheral organs via pathways that are independent of feeding behavior.

The epidemiology of fighting in group-housed laboratory mice.

Injurious home-cage aggression (fighting) in mice affects both animal welfare and scientific validity. It is arguably the most common potentially preventable morbidity in mouse facilities. Existing literature on mouse aggression almost exclusively examines territorial aggression induced by introducing a stimulus mouse into the home-cage of a singly housed mouse (i.e. the resident/intruder test). However, fighting occurring in mice living together in long-term groups under standard laboratory housing conditions has barely been studied. We performed a point-prevalence epidemiological survey of fighting at a research institution with an approximate 60,000 cage census. A subset of cages was sampled over the course of a year and factors potentially influencing home-cage fighting were recorded. Fighting was almost exclusively seen in group-housed male mice. Approximately 14% of group-housed male cages were observed with fighting animals in brief behavioral observations, but only 14% of those cages with fighting had skin injuries observable from cage-side. Thus simple cage-side checks may be missing the majority of fighting mice. Housing system (the combination of cage ventilation and bedding type), genetic background, time of year, cage location on the rack, and rack orientation in the room were significant risk factors predicting fighting. Of these predictors, only bedding type is easily manipulated to mitigate fighting. Cage ventilation and rack orientation often cannot be changed in modern vivaria, as they are baked in by cookie-cutter architectural approaches to facility design. This study emphasizes the need to invest in assessing the welfare costs of new housing and husbandry systems before implementing them.

A Psychometrically Robust Screening Tool To Rapidly Identify Socially Impaired Monkeys In The General Population.

Naturally low-social rhesus macaques exhibit social impairments with direct relevance to autism spectrum disorder (ASD). To more efficiently identify low-social individuals in a large colony, we exploited, refined, and psychometrically assessed the macaque Social Responsiveness Scale (mSRS), an instrument previously derived from the human ASD screening tool. We performed quantitative social behavior assessments and mSRS ratings on a total of N = 349 rhesus macaques (Macaca mulatta) housed in large, outdoor corrals. In one cohort (N = 116), we conducted inter-rater and test-retest reliabilities, and in a second cohort (N = 233), we evaluated the convergent construct and predictive validity of the mSRS-Revised (mSRS-R). Only 17 of the original 36 items demonstrated inter-rater and test-retest reliability, resulting in the 17-item mSRS-R. The mSRS-R showed strong validity: mSRS-R scores robustly predicted monkeys' social behavior frequencies in home corrals. Monkeys that scored 1.5 standard deviations from the mean on nonsocial behavior likewise exhibited significantly more autistic-like traits, and mSRS-R scores predicted individuals' social classification (low-social vs. high-social) with 96% accuracy (likelihood ratio chi-square = 25.07; P < 0.0001). These findings indicate that the mSRS-R is a reliable, valid, and sensitive measure of social functioning, and like the human SRS, can be used as a high-throughput screening tool to identify socially impaired individuals in the general population. LAY SUMMARY: Variation in autistic traits can be measured in humans using the Social Responsiveness Scale (SRS). Here, we revised this scale for rhesus macaques (i.e., the mSRS-R), and showed that macaques exhibit individual differences in mSRS-R scores, and at the behavioral extremes, low-social vs. high-social monkeys exhibit more autistic-like traits. These results suggest that the mSRS-R can be used as a screening tool to rapidly and accurately identify low-social monkeys in the general population. Autism Res 2020, 13: 1465-1475. © 2020 International Society for Autism Research, Wiley Periodicals, Inc.

Neonatal CSF vasopressin concentration predicts later medical record diagnoses of autism spectrum disorder.

Autism spectrum disorder (ASD) is a brain disorder characterized by social impairments. ASD is currently diagnosed on the basis of behavioral criteria because no robust biomarkers have been identified. However, we recently found that cerebrospinal fluid (CSF) concentration of the "social" neuropeptide arginine vasopressin (AVP) is significantly lower in pediatric ASD cases vs. controls. As an initial step in establishing the direction of causation for this association, we capitalized upon a rare biomaterials collection of newborn CSF samples to conduct a quasi-prospective test of whether this association held before the developmental period when ASD first manifests. CSF samples had been collected in the course of medical care of 0- to 3-mo-old febrile infants (n = 913) and subsequently archived at -70 °C. We identified a subset of CSF samples from individuals later diagnosed with ASD, matched them 1:2 with appropriate controls (n = 33 total), and quantified their AVP and oxytocin (OXT) concentrations. Neonatal CSF AVP concentrations were significantly lower among ASD cases than controls and individually predicted case status, with highest precision when cases with comorbid attention-deficit/hyperactivity disorder were removed from the analysis. The associations were specific to AVP, as ASD cases and controls did not differ in neonatal CSF concentrations of the structurally related neuropeptide, OXT. These preliminary findings suggest that a neurochemical marker of ASD may be present very early in life, and if replicated in a larger, prospective study, this approach could transform how ASD is detected, both in behaviorally symptomatic children, and in infants at risk for developing it.

Reorganization of the Primate Dorsal Horn in Response to a Deafferentation Lesion Affecting Hand Function.

The loss of sensory input following a spinal deafferentation injury can be debilitating, and this is especially true in primates when the hand is involved. Although significant recovery of function occurs, little is currently understood about the reorganization of the neuronal circuitry, particularly within the dorsal horn. This region receives primary afferent input from the periphery, and cortical input via the somatosensory subcomponent of the corticospinal tract (S1 CST), and is critically important in modulating sensory transmission, both in normal and lesioned states. To determine how dorsal horn circuitry alters to facilitate recovery post-injury, we used an established deafferentation lesion model (dorsal root/dorsal column) in male monkeys to remove sensory input from just the opposing digits (digits 1-3) of one hand. This results in a deficit in fine dexterity that recovers over several months. Electrophysiological mapping, tract tracing, and immunolabeling techniques were combined to delineate specific changes to dorsal horn input circuitry. Our main findings show that (1) there is complementary sprouting of the primary afferent and S1 CST populations into an overlapping region of the reorganizing dorsal horn; (2) S1 CST and primary afferent inputs connect in different ways within this region to facilitate sensory integration; and (3) there is a loss of larger S1 CST terminal boutons in the affected dorsal horn, but no change in the size profile of the spared/sprouted primary afferent terminal boutons post-lesion. Understanding such changes helps to inform new and targeted therapies that best promote recovery.SIGNIFICANCE STATEMENT Spinal injuries that remove sensation from the hand, can be debilitating, though functional recovery does occur. We examined changes to the neuronal circuitry of the dorsal horn in monkeys following a lesion that deafferented three digits of one hand. Little is understood about dorsal horn circuitry, despite the fact that this region loses most of its normal input after such an injury, and is clearly a major focus of reorganization. We found that both the spared primary afferents and somatosensory corticospinal efferents sprouted in an overlapping region of the dorsal horn after injury, and that larger (presumably faster) corticospinal terminals are lost, suggesting a significantly altered cortical modulation of primary afferents. Understanding this changing circuitry is important for designing targeted therapies.