Acoustic Communication in Rats: Effects of Social Experiences on Ultrasonic Vocalizations as Socio-affective Signals

Molecular insights into enriched environments and behavioral improvements in autism: a systematic review and meta-analysis

Aims

Autism is a multifaceted developmental disorder of the nervous system, that necessitates novel therapeutic approaches beyond traditional medications and psychosomatic therapy, such as appropriate sensory integration training. This systematic mapping review aims to synthesize existing knowledge on enriching environmental interventions as an alternative avenue for improving autism, guiding future research and practice.

Method

A comprehensive search using the terms ASD and Enriched Environment was conducted across PubMed, EMBASE, ISI, Cochrane, and OVID databases. Most of the literature included in this review was derived from animal model experiments, with a particular focus on assessing the effect of EE on autism-like behavior, along with related pathways and molecular mechanisms. Following extensive group discussion and screening, a total of 19 studies were included for analysis.

Results

Enriched environmental interventions exhibited the potential to induce both behavioral and biochemical changes, ameliorating autism-like behaviors in animal models. These improvements were attributed to the targeting of BDNF-related pathways, enhanced neurogenesis, and the regulation of glial inflammation.

Conclusion

This paper underscores the positive impact of enriched environmental interventions on autism through a review of existing literature. The findings contribute to a deeper understanding of the underlying brain mechanisms associated with this intervention.

Effects of social isolation on 50-kHz ultrasonic vocalizations, affective state, cognition, and neurotransmitter concentrations in the ventral tegmental and locus coeruleus of adult rats

Vocal communication, cognition, and affective state are key features of sustained health and wellness, and because vocalizations are often socially-motivated, social experience likely plays a role in these behaviors. The monoaminergic systems of the ventral tegmental area (VTA) and the locus coeruleus (LC) are associated with social and reward processing, vocalization production, and neurotransmitter changes in response to environmental stressors. The effect of social isolation on these complex behaviors and the underlying neural mechanisms is relatively unknown. To add to this body of literature, we randomized adult male Long-Evans rats to control (housed with a cagemate) or isolated (housed individually) conditions and assayed ultrasonic vocalizations, cognition (novel object recognition test), anxiety (elevated plus maze) and anhedonia (sucrose preference test) at 2, 4, 6, 8, and 10 months of age. At 10 months, VTA and LC samples were assayed for dopamine, norepinephrine, and serotonin using high performance liquid chromatography. We tested the hypotheses that isolation 1) diminishes vocalizations and cognition, 2) increases anxiety and depression, and 3) increases levels of dopamine, norepinephrine, and serotonin in the VTA and LC. Results showed isolation significantly reduced vocalization tonality (signal-to-noise ratio) and increased maximum frequency. There were no significant findings for cognition, anxiety, or anhedonia. Dopamine and serotonin and their respective metabolites were significantly increased in the VTA in isolated rats. These findings suggest chronic changes to social condition such as isolation affects vocalization production and levels of VTA neurotransmitters.

Beyond the three-chamber test: toward a multimodal and objective assessment of social behavior in rodents

MAIN: In recent years, substantial advances in social neuroscience have been realized, including the generation of numerous rodent models of autism spectrum disorder. Still, it can be argued that those methods currently being used to analyze animal social behavior create a bottleneck that significantly slows down progress in this field. Indeed, the bulk of research still relies on a small number of simple behavioral paradigms, the results of which are assessed without considering behavioral dynamics. Moreover, only few variables are examined in each paradigm, thus overlooking a significant portion of the complexity that characterizes social interaction between two conspecifics, subsequently hindering our understanding of the neural mechanisms governing different aspects of social behavior. We further demonstrate these constraints by discussing the most commonly used paradigm for assessing rodent social behavior, the three-chamber test. We also point to the fact that although emotions greatly influence human social behavior, we lack reliable means for assessing the emotional state of animals during social tasks. As such, we also discuss current evidence supporting the existence of pro-social emotions and emotional cognition in animal models. We further suggest that adequate social behavior analysis requires a novel multimodal approach that employs automated and simultaneous measurements of multiple behavioral and physiological variables at high temporal resolution in socially interacting animals. We accordingly describe several computerized systems and computational tools for acquiring and analyzing such measurements. Finally, we address several behavioral and physiological variables that can be used to assess socio-emotional states in animal models and thus elucidate intricacies of social behavior so as to attain deeper insight into the brain mechanisms that mediate such behaviors. CONCLUSIONS: In summary, we suggest that combining automated multimodal measurements with machine-learning algorithms will help define socio-emotional states and determine their dynamics during various types of social tasks, thus enabling a more thorough understanding of the complexity of social behavior.

The strain of unfamiliar conspecifics affects stress identification in rats

Humans show distinct social behaviours when we evaluate an individual as being a member of the same group and recognize social similarity to the individual. One example is more accurate identification of emotion in that individual. Our previous studies proposed that rats recognize social similarity to certain strains of unfamiliar rats. It is therefore possible that the strain of unfamiliar conspecifics affects stress identification in rats. Wistar subject rats were allowed to explore a pair of unfamiliar Wistar, Sprague-Dawley (SD), Long-Evans (LE), or Fischer344 (F344) stimulus rats. To induce differences in stress, one of the stimulus rats had received foot shocks immediately before the test. It was found that the subjects showed biased interaction towards the shocked Wistar and SD stimulus rats, but not toward the shocked LE or F344 stimulus rats. Subsequent experiments confirmed that the biased interaction towards the shocked Wistar and SD stimulus rats was driven by stress in these stimulus rats. In addition, the lack of biased interaction towards the shocked LE and F344 stimulus rats did not appear to be due to procedural reasons. The experiment using LE subject rats further confirmed that the shocked LE stimulus rats emitted distress signals. These results suggested that Wistar rats could identify stress in unfamiliar Wistar and SD rats, but not in unfamiliar LE or F344 rats. Therefore, rats appear to recognize social similarity to certain unfamiliar strains of rats.

TrackUSF, a novel tool for automated ultrasonic vocalization analysis, reveals modified calls in a rat model of autism

Background

Various mammalian species emit ultrasonic vocalizations (USVs), which reflect their emotional state and mediate social interactions. USVs are usually analyzed by manual or semi-automated methodologies that categorize discrete USVs according to their structure in the frequency-time domains. This laborious analysis hinders the effective use of USVs as a readout for high-throughput analysis of behavioral changes in animals.

Results

Here we present a novel automated open-source tool that utilizes a different approach towards USV analysis, termed TrackUSF. To validate TrackUSF, we analyzed calls from different animal species, namely mice, rats, and bats, recorded in various settings and compared the results with a manual analysis by a trained observer. We found that TrackUSF detected the majority of USVs, with less than 1% of false-positive detections. We then employed TrackUSF to analyze social vocalizations in Shank3-deficient rats, a rat model of autism, and revealed that these vocalizations exhibit a spectrum of deviations from appetitive calls towards aversive calls.

Conclusions

TrackUSF is a simple and easy-to-use system that may be used for a high-throughput comparison of ultrasonic vocalizations between groups of animals of any kind in any setting, with no prior assumptions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-022-01299-y.

Insulin-like growth factor-2 does not improve behavioral deficits in mouse and rat models of Angelman Syndrome

BACKGROUND

Angelman Syndrome (AS) is a rare neurodevelopmental disorder for which there is currently no cure or effective therapeutic. Since the genetic cause of AS is known to be dysfunctional expression of the maternal allele of ubiquitin protein ligase E3A (UBE3A), several genetic animal models of AS have been developed. Both the Ube3a maternal deletion mouse and rat models of AS reliably demonstrate behavioral phenotypes of relevance to AS and therefore offer suitable in vivo systems in which to test potential therapeutics. One promising candidate treatment is insulin-like growth factor-2 (IGF-2), which has recently been shown to ameliorate behavioral deficits in the mouse model of AS and improve cognitive abilities across model systems.

METHODS

We used both the Ube3a maternal deletion mouse and rat models of AS to evaluate the ability of IGF-2 to improve electrophysiological and behavioral outcomes.

RESULTS

Acute systemic administration of IGF-2 had an effect on electrophysiological activity in the brain and on a metric of motor ability; however the effects were not enduring or extensive. Additional metrics of motor behavior, learning, ambulation, and coordination were unaffected and IGF-2 did not improve social communication, seizure threshold, or cognition.

LIMITATIONS

The generalizability of these results to humans is difficult to predict and it remains possible that dosing schemes (i.e., chronic or subchronic dosing), routes, and/or post-treatment intervals other than that used herein may show more efficacy.

CONCLUSIONS

Despite a few observed effects of IGF-2, our results taken together indicate that IGF-2 treatment does not profoundly improve behavioral deficits in mouse or rat models of AS. These findings shed cautionary light on the potential utility of acute systemic IGF-2 administration in the treatment of AS.

Biological and Acoustic Sex Differences in Rat Ultrasonic Vocalization

The rat model is a useful tool for understanding peripheral and central mechanisms of laryngeal biology. Rats produce ultrasonic vocalizations (USVs) that have communicative intent and are altered by experimental conditions such as social environment, stress, diet, drugs, age, and neurological diseases, validating the rat model's utility for studying communication and related deficits. Sex differences are apparent in both the rat larynx and USV acoustics and are differentially affected by experimental conditions. Therefore, the purpose of this review paper is to highlight the known sex differences in rat USV production, acoustics, and laryngeal biology detailed in the literature across the lifespan.

Translational outcomes in a full gene deletion of ubiquitin protein ligase E3A rat model of Angelman syndrome

Angelman syndrome (AS) is a rare neurodevelopmental disorder characterized by developmental delay, impaired communication, motor deficits and ataxia, intellectual disabilities, microcephaly, and seizures. The genetic cause of AS is the loss of expression of UBE3A (ubiquitin protein ligase E6-AP) in the brain, typically due to a deletion of the maternal 15q11-q13 region. Previous studies have been performed using a mouse model with a deletion of a single exon of Ube3a. Since three splice variants of Ube3a exist, this has led to a lack of consistent reports and the theory that perhaps not all mouse studies were assessing the effects of an absence of all functional UBE3A. Herein, we report the generation and functional characterization of a novel model of Angelman syndrome by deleting the entire Ube3a gene in the rat. We validated that this resulted in the first comprehensive gene deletion rodent model. Ultrasonic vocalizations from newborn Ube3am-/p+ were reduced in the maternal inherited deletion group with no observable change in the Ube3am+/p- paternal transmission cohort. We also discovered Ube3am-/p+ exhibited delayed reflex development, motor deficits in rearing and fine motor skills, aberrant social communication, and impaired touchscreen learning and memory in young adults. These behavioral deficits were large in effect size and easily apparent in the larger rodent species. Low social communication was detected using a playback task that is unique to rats. Structural imaging illustrated decreased brain volume in Ube3am-/p+ and a variety of intriguing neuroanatomical phenotypes while Ube3am+/p- did not exhibit altered neuroanatomy. Our report identifies, for the first time, unique AS relevant functional phenotypes and anatomical markers as preclinical outcomes to test various strategies for gene and molecular therapies in AS.

Subthalamic nucleus mediates the modulation on cocaine self-administration induced by ultrasonic vocalization playback in rats

Drug intake is known to be under the influence of social context. We have recently shown that presence of a peer influences drug intake in both rats and humans. Whether or not social acoustic communications between the peers play a role during cocaine or sucrose self-administration (SA) was investigated here using playback of ultrasonic vocalizations (USVs) at 50 and 22 kHz, conveying, respectively, positive and negative internal affective states in adult rats. To assess the neurobiological substrate of a potential USV influence on drug and food intake, we tested the effects of subthalamic nucleus (STN) lesions, given its role in emotional and motivational processes. In sham-control rats, playback of USV associated with positive affective states induced long-term decreased cocaine consumption, while USV associated with negative affective states induced short-term increase. Interestingly, no effect of USV playback was observed on sucrose intake, whatever the frequency. STN lesions abolished the influence of USV on cocaine intake, highlighting the influence of STN in emotional processes induced by USV emitted by a peer. These results show how acoustic social communication is important to regulate drug intake in rats and how STN modulation could interfere with addiction processes.

Social experience during adolescence in female rats increases 50 kHz ultrasonic vocalizations in adulthood, without affecting anxiety-like behavior

Adolescents are highly motivated to engage in social interactions, and researchers have hypothesized that positive social relationships during adolescence can have long term, beneficial effects on stress reactivity and mental well-being. Studies of laboratory rodents provide the opportunity to investigate the relationship between early social experiences and later behavioral and physiological responses to stressors. In this study, female Lister-hooded rats (N = 12 per group) were either (a) provided with short, daily encounters (10 min/day) with a novel partner during mid-adolescence (postnatal day 34-45; "social experience," SE, subjects) or (b) underwent the same protocol with a familiar cagemate during mid-adolescence ("control experience," CE, subjects), or (c) were left undisturbed in the home cage (non-handled "control," C, subjects). When tested in adulthood, the groups did not differ in behavioral responses to novel environments (elevated plus maze, open field, and light-dark box) or in behavioral and physiological (urinary corticosterone) responses to novel social partners. However, SE females emitted significantly more 50 kHz ultrasonic vocalizations than control subjects both before and after social separation from a familiar social partner, which is consistent with previous findings in male rats. Thus, enhanced adolescent social experience appears to have long-term effects on vocal communication and could potentially modulate adult social relationships.

Cognitive Phenotypes for Biomarker Identification in Mental Illness: Forward and Reverse Translation

Psychiatric illness has been acknowledged for as long as people were able to describe behavioral abnormalities in the general population. In modern times, these descriptions have been codified and continuously updated into manuals by which clinicians can diagnose patients. None of these diagnostic manuals have attempted to tie abnormalities to neural dysfunction however, nor do they necessitate the quantification of cognitive function despite common knowledge of its ties to functional outcome. In fact, in recent years the National Institute of Mental Health released a novel transdiagnostic classification, the Research Domain Criteria (RDoC), which utilizes quantifiable behavioral abnormalities linked to neurophysiological processes. This reclassification highlights the utility of RDoC constructs as potential cognitive biomarkers of disease state. In addition, with RDoC and cognitive biomarkers, the onus of researchers utilizing animal models no longer necessitates the recreation of an entire disease state, but distinct processes. Here, we describe the utilization of constructs from the RDoC initiative to forward animal research on these cognitive and behavioral processes, agnostic of disease. By linking neural processes to these constructs, identifying putative abnormalities in diseased patients, more targeted therapeutics can be developed.

Avoiding escalation from play to aggression in adult male rats: The role of ultrasonic calls

Play fighting is most commonly associated with juvenile animals, but in some species, including rats, it can continue into adulthood. Post-pubertal engagement in play fighting is often rougher and has an increased chance of escalation to aggression, making the use of play signals to regulate the encounter more critical. During play, both juvenile and adult rats emit many 50-kHz calls and some of these may function as play facilitating signals. In the present study, unfamiliar adult male rats were introduced in a neutral enclosure and their social interactions were recorded. While all pairs escalated their playful encounters to become rougher, only the pairs in which one member was devocalized escalated to serious biting. A Monte Carlo shuffling technique was used for the analysis of the correlations between the overt playful and aggressive actions performed and the types and frequencies of various 50-kHz calls that were emitted. The analysis revealed that lower frequency (20-30kHz) calls with a flat component maybe particularly critical for de-escalating encounters and so allowing play to continue. Moreover, coordinating calls reciprocally, with either the same call mimicked in close, temporal association or with complementary calls emitted by participants as they engage in complementary actions (e.g., attacking the nape, being attacked on the nape), appeared to be ways with which calls could be potentially used to avoid escalation to aggression and so sustain playful interactions.

Simultaneous Changes in Sleep, qEEG, Physiology, Behaviour and Neurochemistry in Rats Exposed to Repeated Social Defeat Stress

Depression is a heterogeneous disorder characterized by alterations at psychological, behavioural, physiological, neurophysiological, and neurochemical levels. Social stress is a prevalent stress in man, and the repeated social defeat stress model in rats has been proposed as being the rodent equivalent to loss of control, which in subordinate animals produces alterations that resemble several of the cardinal symptoms found in depressed patients. Here, rats followed a resident-intruder protocol for 4 consecutive days during which behavioural, physiological, and electroencephalographic (EEG) parameters were simultaneously monitored in subordinate rats. On day 5, prefrontal dopamine (DA) and hippocampal serotonin (5-HT) as well as corticosterone were measured in submissive rats that had visual, acoustic, and olfactory (but no physical) contact with a dominant, resident conspecific rat. Socially defeated rats demonstrated increases in ultrasonic vocalizations (20-25 KHz), freezing, submissive defensive behaviour, inactivity, and haemodynamic response, while decreases were found in repetitive grooming behaviour and body weight. Additionally, alterations in the sleep-wake architecture were associated with reduced active waking, enhanced light sleep, and increased frequency of transitions from light sleep to quiet wakefulness, indicating sleep instability. Moreover, the attenuation of EEG power over the frequency range of 4.2-30 Hz, associated with a sharp transient increase in delta oscillations, appeared to reflect increased brain activity and metabolism in subordinate animals. These EEG changes were synchronous with a marked increase in body temperature and a decrease in locomotor activity. Furthermore, psychosocial stress consistently increased 5-HT, DA, and corticosterone levels. The increased levels of cortical DA and hippocampal 5-HT during social threat may reflect a coping mechanism to promote alertness and psychological adaptation to provocative and threatening stimuli. These neurophysiological changes are hypothesized to be the consequence of dynamics in monoamine systems, which could be useful markers for disease progression in the aetiology of depression.

From Play to Aggression: High-Frequency 50-kHz Ultrasonic Vocalizations as Play and Appeasement Signals in Rats

When rats engage in playful interactions, they emit appetitive 50-kHz ultrasonic vocalizations (USVs). We investigated the role of 50-kHz USVs in the playful behavior of both juvenile and adult rats. A cohort of juvenile rats was surgically devocalized and allowed to interact with either devocalized or intact partners as juveniles and again as adults. A substantial decrease in playful motivation was seen for pairs of devocalized rats, as well as all intact rats housed with devocalized ones. In pairs in which at least one partner could vocalize, there was no difference in the number of playful interactions as compared to controls. Further investigation revealed that, within the playful episode itself, 50-kHz USVs are more likely to appear before a playful attack is launched than after, regardless of the attacking partner's ability to vocalize, and when one partner is pinned on its back by another, it is the rat that is on top that is more likely to emit 50-kHz USVs. These findings suggest that, for juveniles, 50-kHz USVs may have a critical function in maintaining and facilitating playful motivation, but a more limited role in signaling playful actions. In adults, however, whatever the motivational role of such calling may be, the various kinds of USVs appear to serve critical communicatory functions. For instance, when pairs of adult males that are unfamiliar with one another encounter each other in a neutral arena, they play together, but if one partner is devocalized, there is a significantly higher likelihood that the interaction will escalate to become aggressive. While the relative roles of appetitive 50-kHz and aversive 22-kHz USVs in this context remain to be determined, our overall findings for play in both juveniles and adults suggest that 50-kHz USVs likely have multiple functions, with different functions being more prevalent at some ages and contexts than others.

Social dysfunction after pediatric traumatic brain injury: A translational perspective

Social dysfunction is common after traumatic brain injury (TBI), contributing to reduced quality of life for survivors. Factors which influence the development or persistence of social deficits after injury remain poorly understood, particularly in the context of ongoing brain maturation during childhood and adolescence. Aberrant social interactions have recently been modeled in adult and juvenile rodents after experimental TBI, providing an opportunity to gain new insights into the underlying neurobiology of these behaviors. Here, we review our current understanding of social dysfunction in both humans and rodent models of TBI, with a focus on brain injuries acquired during early development. Modulators of social outcomes are discussed, including injury-related and environmental risk and resilience factors. Disruption of social brain network connectivity and aberrant neuroendocrine function are identified as potential mechanisms of social impairments after pediatric TBI. Throughout, we highlight the overlap and disparities between outcome measures and findings from clinical and experimental approaches, and explore the translational potential of future research to prevent or ameliorate social dysfunction after childhood TBI.

Conspecific Interactions in Adult Laboratory Rodents: Friends or Foes?

Interactions between adult conspecifics, including sexual behaviors, affiliation, and aggression are crucial for the well-being, survival, and reproduction of mammals. This holds true for any mammalian species, but certainly for humans: An inability to optimally navigate the social system can have a strong negative impact on physical and mental health. Translational rodent models have been used for decades to unravel the neural pathways and substrates involved in normal and abnormal conspecific interactions. Researchers in the field of translational social neuroscience face a double challenge: Not only do they need to pay considerable attention to the behavioral ecology of their model species or their ancestors, they also have to expect a relatively large variability in behavior and adjust their experimental design accordingly. In this chapter, we will lay out traditional and novel rodent models and paradigms to study sexual, affiliative, and aggressive interactions among adult conspecifics. We will discuss the merits and main findings and briefly consider the most promising novel directions. Finally, we review the modulatory involvement of two major players in mammal social interaction: the central oxytocin and vasopressin system.