Evidence for social cooperation in rodents by automated maze

In search of prosociality in rodents: A scoping review

Studying prosociality in rodents can provide insight into brain mechanisms potentially related to neurodevelopmental disorders known to impact social behaviors (e.g., autism spectrum disorder). While many studies have been published suggesting promising models, current knowledge remains scattered, including potential factors mediating prosocial behaviors in rodents. Prosocial behavior is characterized by an action done to benefit another or promote their well-being. The goal of this scoping review is to characterize current findings regarding prosocial paradigms in rodents, highlight current gaps in reporting, and identify factors shown to be important in mediating prosocial responses in rodents. Five databases were consulted in search of relevant studies published between 2000 and 2020 (APA PsycInfo, Embase, MEDLINE, Scopus, Web of Science). An update using a semi-supervised machine learning approach (ASReview) was then conducted to collect studies from 2021-2023. In total, 80 articles were included. Findings were the following: (1) Three categories of prosocial paradigm were extracted: cooperation, helping, and sharing tasks, (2) Rodents showed the ability to perform prosocial actions in all three categories, (3) Significant gaps in reported methodologies (e.g., failure to report animals' characteristics, housing conditions, and/or experimental protocol) and mediating factors (e.g., sex, strain, housing, food restriction) were found, and (4) Behaviors are determinant when investigating prosociality in rodents, however many studies omitted to include such analyses. Together these results inform future studies on the impact of mediating factors and the importance of behavioral analyses on the expression of prosocial behaviors in rodents.

A translational neuroscience perspective on loneliness: Narrative review focusing on social interaction, illness and oxytocin

This review addresses key findings on loneliness from the social, neurobiological and clinical fields. From a translational perspective, results from studies in humans and animals are included, with a focus on social interaction, mental and physical illness and the role of oxytocin in loneliness. In terms of social interactions, lonely individuals tend to exhibit a range of abnormal behaviors based on dysfunctional social cognitions that make it difficult for them to form meaningful relationships. Neurobiologically, a link has been established between loneliness and the hypothalamic peptide hormone oxytocin. Since social interactions and especially social touch regulate oxytocin signaling, lonely individuals may have an oxytocin imbalance, which in turn affects their health and well-being. Clinically, loneliness is a predictor of physical and mental illness and leads to increased morbidity and mortality. There is evidence that psychopathology is both a cause and a consequence of loneliness. The final section of this review summarizes the findings from social, neurobiological and clinical perspectives to present a new model of the complex construct of loneliness.

Protocol for evaluating mutualistic cooperative behavior in mice using a water-reward task assay

Social cooperation is fundamentally important for group animals but rarely studied in mice because of their natural aggressiveness. Here, we present a new water-reward assay to investigate mutualistic cooperative behavior in mice. We describe the construction of the apparatus and provide details of the procedures and analysis for investigators to characterize and quantify the mutualistic cooperative behavior. This protocol has been validated in mice and can be used for investigating mechanisms of cooperation. For complete details on the use and execution of this protocol, please refer to Zhang et al. and Wang et al.1,2.

Examination of the joint Simon effect in rats: Changes in task performance based on actions of the partner

Nonhuman animals have demonstrated various cooperative behaviors; however, many examples can be interpreted as individual contributions to a task rather than true behavioral coordination. In this study, we used the joint Simon task in rats to determine whether the presence of and task sharing with a partner affected performance in a joint activity. Rats were trained to discriminate between two auditory stimuli (3 and 12 kHz tones) and individually performed an auditory Simon task. They were paired with another rat and tested to perform half of the task, while the other rat performed the other half (joint task condition). The Simon effect was confirmed when the two rats completed half of a joint task. In contrast, when they were placed side by side but only one rat completed half of the task, the Simon effect was not observed. Further analyses revealed that the Simon effect observed in the joint task could not be explained by the simple addition of the two half tasks. In conclusion, task sharing affected individual performance in rats.

From grouping and cooperation to menstruation: Spiny mice (Acomys cahirinus) are an emerging mammalian model for sociality and beyond

While spiny mice are primarily used as a model for Type II diabetes and for studying complex tissue regeneration, they are also an emerging model for a variety of studies examining hormones, behavior, and the brain. We began studying the spiny mouse to take advantage of their highly gregarious phenotype to examine how the brain facilitates large group-living. However, this unique rodent can be readily bred and maintained in the lab and can be used to ask a wide variety of scientific questions. In this brief communication we provide an overview of studies that have used spiny mice for exploring physiology and behavior. Additionally, we describe how the spiny mouse can serve as a useful model for researchers interested in studying precocial development, menstruation, cooperation, and various grouping behaviors. With increasingly available technological advancements for non-traditional organisms, spiny mice are well-positioned to become a valuable organism in the behavioral neuroscience community.

A new paradigm of learned cooperation reveals extensive social coordination and specific cortical activation in mice

Cooperation is a social behavior crucial for the survival of many species, including humans. Several experimental paradigms have been established to study cooperative behavior and related neural activity in different animal species. Although mice exhibit limited cooperative capacity in some behavioral paradigms, it is still interesting to explore their cooperative behavior and the underlying neural mechanisms. Here, we developed a new paradigm for training and testing cooperative behavior in mice based on coordinated lever-pressing and analyzed social interactions between the animals during cooperation. We observed extensive social contact and waiting behavior in cooperating animals, with the number of such events positively correlated with the success of cooperation. Using c-Fos immunostaining and a high-speed volumetric imaging with synchronized on-the-fly scan and readout (VISoR) system, we further mapped whole-brain neuronal activity trace following cooperation. Significantly higher levels of c-Fos expression were observed in cortical areas including the frontal pole, motor cortex, anterior cingulate area, and prelimbic area. These observations highlight social interaction and coordination in cooperative behavior and provide clues for further study of the underlying neural circuitry mechanisms.

Observational learning in rats: Interplay between demonstrator and observer behavior

BACKGROUND

Observational learning is a vital skill for survival. This form of learning has been seen in humans and certain non-human animals. However, the neural circuitry underlying this form of learning is still poorly understood.

NEW METHOD

To better understand the factors underlying successful observation in rats, we employed a task where an observer must base its behavior on that of a demonstrator rat to identify a reward location. A comparison was made of behavior during a social and non-social observation condition.

RESULTS

Observers oriented more, responded faster and omitted less responses in the social compared to the non-social condition. Observer performance was also linked to initial orientation, proximity, and the manner in which the demonstrator rat performed the task.

COMPARISON WITH EXISTING METHOD

Previous work on observational learning encompassed multiple exposures to a single solution over days or weeks. The current method provides data from multiple individual novel observational learning trials, leading to much faster and more robust social learning. This method provides a clearly defined interval in which observation must take place. Allowing for precise tracking of both the observer and demonstrator behavior during the learning period.

CONCLUSIONS

This study highlights observer and demonstrator interplay in successful observational learning and provides a novel method for analyzing social behavior in rodents.

Neural basis of prosocial behavior

The ability to behave in ways that benefit other individuals' well-being is among the most celebrated human characteristics crucial for social cohesiveness. Across mammalian species, animals display various forms of prosocial behaviors - comforting, helping, and resource sharing - to support others' emotions, goals, and/or material needs. In this review, we provide a cross-species view of the behavioral manifestations, proximate and ultimate drives, and neural mechanisms of prosocial behaviors. We summarize key findings from recent studies in humans and rodents that have shed light on the neural mechanisms underlying different processes essential for prosocial interactions, from perception and empathic sharing of others' states to prosocial decisions and actions.

Evolution and neural representation of mammalian cooperative behavior

Cooperation is common in nature and is pivotal to the development of human society. However, the details of how and why cooperation evolved remain poorly understood. Cross-species investigation of cooperation may help to elucidate the evolution of cooperative strategies. Thus, we design an automated cooperative behavioral paradigm and quantitatively examine the cooperative abilities and strategies of mice, rats, and tree shrews. We find that social communication plays a key role in the establishment of cooperation and that increased cooperative ability and a more efficient cooperative strategy emerge as a function of the evolutionary hierarchy of the tested species. Moreover, we demonstrate that single-unit activities in the orbitofrontal and prelimbic cortex in rats represent neural signals that may be used to distinguish between the cooperative and non-cooperative tasks, and such signals are distinct from the reward signals. Both signals may represent distinct components of the internal drive for cooperation.

Social Behavior and Ultrasonic Vocalizations in a Genetic Rat Model Haploinsufficient for the Cross-Disorder Risk Gene Cacna1c

The top-ranked cross-disorder risk gene CACNA1C is strongly associated with multiple neuropsychiatric dysfunctions. In a recent series of studies, we applied a genomically informed approach and contributed extensively to the behavioral characterization of a genetic rat model haploinsufficient for the cross-disorder risk gene Cacna1c. Because deficits in processing social signals are associated with reduced social functioning as commonly seen in neuropsychiatric disorders, we focused on socio-affective communication through 22-kHz and 50-kHz ultrasonic vocalizations (USV). Specifically, we applied a reciprocal approach for studying socio-affective communication in sender and receiver by including rough-and-tumble play and playback of 22-kHz and 50-kHz USV. Here, we review the findings obtained in this recent series of studies and link them to the key features of 50-kHz USV emission during rough-and-tumble play and social approach behavior evoked by playback of 22-kHz and 50-kHz USV. We conclude that Cacna1c haploinsufficiency in rats leads to robust deficits in socio-affective communication through 22-kHz and 50-kHz USV and associated alterations in social behavior, such as rough-and-tumble play behavior.

Protocol for quantitative assessment of social cooperation in mice

Social cooperation in rodents was recently validated in rats, and we recently successfully applied a modified automated analysis to mice. Here, we describe a detailed procedure for using this paradigm in mice that relies on reward-based mutual communication that is automatically detected by a software algorithm embedded in the custom-made equipment. We also describe exemplary results of analyses in mice as a guide to broader neuroscience research applications employing transgenic knockout mice modeling neuropsychiatric disorders and mice of various ages.

For complete details on the use and execution of this protocol, please refer to Han et al. (2020).

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Detailed protocol for performing customized social cooperation tests in mice

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Detailed guidelines for analyzing social cooperation in mice

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Troubleshooting of the most common pitfalls associated with the procedure

Differentially altered social dominance- and cooperative-like behaviors in Shank2- and Shank3-mutant mice

BACKGROUND

Recent progress in genomics has contributed to the identification of a large number of autism spectrum disorder (ASD) risk genes, many of which encode synaptic proteins. Our understanding of ASDs has advanced rapidly, partly owing to the development of numerous animal models. Extensive characterizations using a variety of behavioral batteries that analyze social behaviors have shown that a subset of engineered mice that model mutations in genes encoding Shanks, a family of excitatory postsynaptic scaffolding proteins, exhibit autism-like behaviors. Although these behavioral assays have been useful in identifying deficits in simple social behaviors, alterations in complex social behaviors remain largely untested.

METHODS

Two syndromic ASD mouse models-Shank2 constitutive knockout [KO] mice and Shank3 constitutive KO mice-were examined for alterations in social dominance and social cooperative behaviors using tube tests and automated cooperation tests. Upon naïve and salient behavioral experience, expression levels of c-Fos were analyzed as a proxy for neural activity across diverse brain areas, including the medial prefrontal cortex (mPFC) and a number of subcortical structures.

FINDINGS

As previously reported, Shank2 KO mice showed deficits in sociability, with intact social recognition memory, whereas Shank3 KO mice displayed no overt phenotypes. Strikingly, the two Shank KO mouse models exhibited diametrically opposed alterations in social dominance and cooperative behaviors. After a specific social behavioral experience, Shank mutant mice exhibited distinct changes in number of c-Fos⁺ neurons in the number of cortical and subcortical brain regions.

CONCLUSIONS

Our results underscore the heterogeneity of social behavioral alterations in different ASD mouse models and highlight the utility of testing complex social behaviors in validating neurodevelopmental and neuropsychiatric disorder models. In addition, neural activities at distinct brain regions are likely collectively involved in eliciting complex social behaviors, which are differentially altered in ASD mouse models.

Exposure to Hedione Increases Reciprocity in Humans

Cooperation among unrelated humans is frequently regarded as a defining feature in the evolutionary success of our species. Whereas, much research has addressed the strategic and cognitive mechanisms that underlie cooperation, investigations into chemosensory processes have received very limited research attention. To bridge that gap, we build on recent research that has identified the chemically synthesized odorant Hedione (HED) as a ligand for the putative human pheromone receptor (VN1R1) expressed in the olfactory mucosa, and hypothesize that exposure to HED may increase reciprocity. Applying behavioral economics paradigms, the present research shows that exposure to the ligand causes differentiated behavioral effects in reciprocal punishments (Study 1) as well as rewards (Study 2), two types of behaviors that are frequently regarded as essential for the development and maintenance of cooperation.