Neural circuits of social behaviors: Innate yet flexible

Sex Differences in Sexual Motivation Among U.S. Residents 57-85 Years of Age

Sexual motivation includes proceptivity (mental or physical pursuit of sexual gratification) and receptivity (openness to having sex initiated by someone else). The roles of these two components are not well understood in older adults past reproductive age. We quantify these components and their associations with sexual activity along with differences in sex, age, partner status, health, reproductive steroids and other demographic variables collected during home interviews for the National Social Life, Health, and Aging Project's nationally representative sample of 3005, 57-85 years old community-dwelling U.S. residents. The majority of older adults had sex and age had only a modest association with their sexual motivation. Proceptive and receptive sexual motivation were independent of each other and each was associated with higher odds of having sex more frequently. Relative to women, men reported higher levels of sexual proceptivity, controlling for demographic and biological variables such as medications, diseases, education, partner status, reproductive steroid levels, and age. Women reported higher sexual receptivity than did men. Although men had higher free salivary testosterone levels, it was associated with higher proceptivity and receptivity within both men and women. DHEA and estradiol were also associated with variations in sexual motivation. Nonetheless, sex differences in each component of sexual motivation remained after controlling for reproductive steroid levels along with demographics and partner status. Having a positive emotional relationship was associated with higher proceptive sexual motivation in women but not in men.

A reduced ability to discriminate social from non-social touch at the circuit level may underlie social avoidance in autism

Social touch is critical for communication to impart emotions and intentions. However, certain autistic individuals experience aversion to social touch. Here, we used Neuropixels probes to record neural responses to social vs. non-social interactions in somatosensory cortex, tail of striatum, and basolateral amygdala. We find that wild type mice show aversion to repeated presentations of an inanimate object but not of another mouse. Cortical neurons are modulated especially by touch context (social vs. object), while striatal neurons change their preference depending on whether mice could choose or not to interact. In contrast, Fmr1 knockout (KO) mice, a model of autism, find social and non-social interactions equally aversive, especially at close proximity, and their cortical/striatal neurons are less able to discriminate social valence. A linear model shows that the encoding of certain avoidance/aversive behaviors in cortical neuron activity differed between genotypes. Thus, a reduced capacity to represent social stimuli at the circuit level may underlie social avoidance in autism.

Differential Functions of Oxytocin Receptor-Expressing Neurons in the Ventromedial Hypothalamus in Social Stress Responses: Induction of Adaptive and Maladaptive Coping Behaviors

BACKGROUND

The flexibility to adjust actions and attitudes in response to varying social situations is a fundamental aspect of adaptive social behavior. Adaptive social behaviors influence an individual's vulnerability to social stress. While it has been proposed that oxytocin is a facilitator of active coping behaviors during social stress, the exact mechanisms remain unknown.

METHODS

Using a social defeat stress paradigm in male mice, we identified the distribution of oxytocin receptor (OXTR)-expressing neurons in the ventrolateral part of the ventromedial hypothalamus (vlVMH) that are activated during stress by detection of c-Fos protein expression. We then investigated the role of vlVMH OXTR-expressing neurons in social defeat stress responses by chemogenetic methods or deletion of local OXTRs. The social defeat posture was measured for quantification of adaptive social behavior during repeated social stress.

RESULTS

Social defeat stress activated OXTR-expressing neurons rather than estrogen receptor 1-expressing neurons in the rostral vlVMH. OXTR-expressing neurons in the vlVMH were glutamatergic. Chemogenetic activation of vlVMH OXTR-expressing neurons facilitated exhibition of the social defeat posture during exposure to social stress, while local OXTR deletion suppressed it. In contrast, overactivation of vlVMH-OXTR neurons induced generalized social avoidance after exposure to chronic social defeat stress. Neural circuits for the social defeat posture centered on OXTR-expressing neurons were identified by viral tracers and c-Fos mapping.

CONCLUSIONS

vlVMH OXTR-expressing neurons are a functionally unique population of neurons that promote active coping behavior during social stress, but their excessive and repetitive activation under chronic social stress impairs subsequent social behavior.

Convergent effects of peptides on the initiation of feeding motor programs in the mollusk Aplysia

Neuropeptides configure the feeding network of Aplysia. For example, egestive activity is promoted by small cardioactive peptide (SCP), and ingestive activity is promoted by a combination of feeding circuit activating peptide (FCAP) and cerebral peptide 2 (CP-2). In addition, SCP and FCAP/CP-2 have a common network effect that does not contribute to motor program specification. They increase the excitability of an interneuron, B63. In this report, we further characterized the effects of peptides on B63. We performed voltage-clamp experiments and used a step protocol to look at steady-state currents. We found that SCP and FCAP/CP-2 both induced an inward current that was virtually absent in low-sodium saline. Previous work has established that B63 is unusual in the feeding circuit in that subthreshold depolarizations are autonomously generated that can trigger motor programs. Here, we show that this autonomous activity is more frequent in the presence of peptides. Previous studies have also shown that activity of the feeding central pattern generator (CPG) can be initiated by neurons that excite B63, e.g., by cerebral buccal interneuron 2 (CBI-2), a projection neuron that triggers biting-like motor programs. Here, we show that the latency of CBI-2-induced activity is decreased by stimulation of the esophageal nerve (EN) (which releases endogenous SCP). These results, taken together with previous results, indicate that peptides that act divergently to configure network activity additionally act convergently to promote motor program induction. We present data that suggest that this arrangement facilitates brief switches between ingestive and egestive motor activity.NEW & NOTEWORTHY The activity of most networks is affected by multiple neuromodulators. Studies that have sought to determine why this is the case have focused on how the effects of one modulator differ from those of another (how modulators uniquely determine motor output). This study differs in that we ask why a convergent (common) network modification is important. We show that it can promote program induction and present data that suggest this may have consequences for task switching.

Integrating innate and learned behavior through brain circuits

Understanding how innate predispositions and learned experiences interact to shape behavior is a central question in systems neuroscience. Traditionally, innate behaviors, that is, those present without prior learning and governed by evolutionarily conserved neural circuits, have been studied separately from learned behaviors, which depend on experience and neural plasticity. This division has led to a compartmentalized view of behavior and neural circuit organization. Increasing evidence suggests that innate and learned behaviors are not independent, but rather deeply intertwined, with plasticity evident even in circuits classically considered 'innate'. In this opinion, we highlight examples across species that illustrate the dynamic interaction between these behavioral domains and discuss the implications for unifying theoretical and empirical frameworks. We argue that a more integrative approach, namely one that acknowledges the reciprocal influences of innate and learned processes, is essential for advancing our understanding of how neuronal activity drives complex behaviors.

Brain circuits that regulate social behavior

Social interactions are essential for the survival of individuals and the reproduction of populations. Social stressors, such as social defeat and isolation, can lead to emotional disorders and cognitive impairments. Furthermore, dysfunctional social behaviors are hallmark symptoms of various neuropsychiatric disorders, including autism spectrum disorder (ASD) and post-traumatic stress disorder (PTSD). Consequently, understanding the neural circuit mechanisms underlying social behaviors has become a major focus in neuroscience. Social behaviors, which encompass a wide range of expressions and phases, are regulated by complex neural networks. In this review, we summarize recent progress in identifying the circuits involved in different types of social behaviors, including general social investigation, social preference, mating, aggression, parenting, prosocial behaviors, and dominance behaviors. We also outline the circuit mechanisms associated with social deficits in neuropsychiatric disorders, such as ASD, schizophrenia, and PTSD. Given the pivotal role of rodents in social behavior research, our review primarily focuses on neural circuits in these animals. Finally, we propose future research directions, including the development of specific behavioral paradigms, the identification of circuits involved in motor output, the integration of activity, transcriptome, and connectome data, the multifunctional roles of neurons with multiple targets, and the interactions among multiple brain regions.

Mom genes and dad genes: genomic imprinting in the regulation of social behaviors

Genomic imprinting is an epigenetic phenomenon in mammals that affects brain development and behavior. Imprinting involves the regulation of allelic expression for some genes in offspring that depends on whether alleles are inherited from mothers compared to fathers, and is thought to provide parental control over offspring social behavior phenotypes. Imprinted gene expression is prevalent in the mammalian brain, and human imprinted gene mutations are associated with neurodevelopmental disorders and neurodivergent social behavior in Prader-Willi Syndrome, Angelman Syndrome, and autism. Here, we provide a review of the evidence that imprinted genes influence social behaviors across major neurodevelopmental stages in humans and mouse animal models that include parent-infant interactions, juvenile sociability, and adult aggression, dominance, and sexual behavior.

The rhythm of sequential behavioral transitions: Neuromodulatory dynamics and male sexual behavior

In this issue of Neuron, Miyasaka et al.1 demonstrate that the sequential transitions of male sexual behaviors are orchestrated by dual rhythms of dopamine and acetylcholine signaling generated in the ventral shell of the nucleus accumbens.

Social experience is associated with a differential role of aromatase neurons in sexual behavior and territorial aggression in male mice

Aromatase (Aro+) neurons located in the Bed Nucleus of the Stria Terminalis (BNST) are crucial for the display of both sexual behavior and territorial aggression in naive male mice. The postero-dorsal part of the Medial Amygdala (MeApd) also contains Aro + neurons that are required for territorial aggression, but these neurons seem dispensable for the display of sexual behavior in naive animals. However, little is known about how Aro + neuron circuitry is influenced by social experience. Using a combination of chemogenetics, activity mapping and retrograde viral tracing, we show that social experience modulates Aro + neurons during sexual behavior and territorial aggression. Chemogenetic inhibition of BNST Aro + neurons in socially experienced male mice revealed that these neurons are required for territorial aggression, but not for sexual behavior. Behavior testing in experienced animals showed a specific increase in activation in the vomeronasal organ (VNO) and the Medial Amygdala (MeA) after sexual behavior but not territorial aggression, assessed by Egr1 expression. We also observed an increase of Egr1 cells in the medial Preoptic Area (mPOA), a brain region implicated in the display of sexual behavior. Combined retrograde viral tracing and Egr1 immunodetection showed that a subset of the activated cells in the MeA are Aro + neurons projecting to the mPOA. These results highlight that social experience induces a differential neural activity in the circuitry controlling sexual behavior and aggression, which include MeA Aro + neurons projecting to the mPOA.

A review of the effects of different types of social behaviors on the recruitment of neuropeptides and neurotransmitters in the nucleus accumbens

There is a lack of understanding of the neural mechanisms regulating the rewarding effects of social interactions. A significant contributor to this lack of clarity is the diversity of social behaviors and animal models utilized to investigate mechanisms. Other sources of the lack of clarity are the diversity of brain regions that can regulate social reward and the diversity of signaling pathways that regulate reward. To provide some clarity into the mechanisms of social reward, this review focused on the brain region most implicated in reward for multiple stimuli, the nucleus accumbens, and surveyed (systematically reviewed) studies that investigated the relationship between social interaction and five signaling systems implicated in the regulation of reward and social behavior: oxytocin, vasopressin, serotonin, opioids and endocannabinoids. Moreover, all of these studies were organized by the type of social behavior studied: affiliative interactions, play behavior, aggression, social defeat, sex behavior, pair-bonding, parental behavior and social isolation. From this survey and organization, this review concludes that oxytocin, endocannabinoids and mu-opioid receptors in the nucleus accumbens positively regulate the rewarding social behaviors, and kappa-opioid receptors negatively regulate the rewarding social behaviors. The opposite profile is observed for these signaling systems for the aversive social behaviors. More studies are needed to investigate the directional role of the serotonin system in the nucleus accumbens in the regulation of many types of social behaviors, and vasopressin likely does not act in the nucleus accumbens in the regulation of the valence of social behaviors. Many of these different signaling systems are also interdependent of one another in the regulation of different types of social behaviors. Finally, the interaction of these signaling systems with dopamine in the nucleus accumbens is briefly discussed.

The medial amygdala's neural circuitry: Insights into social processing and sex differences

The amygdala, a critical part of the limbic system, is essential for processing social stimuli and regulating stress responses. Among its various neuronal nuclei, the medial amygdala (MeA) remains one of the least studied in humans. The MeA plays a key role in receiving inputs from the olfactory system through pheromones, as well as from crucial areas such as the hypothalamus, hippocampus, and reward system. This allows the MeA to integrate external stimuli with the organism's internal state, finetuning social interactions, endocrine responses, and innate behaviors. Recent advances in neuroscience have highlighted the sex differences of the MeA and how they influence behavior and environmental perception. Understanding these sexspecific variations in brain structures, like the MeA in rodents, is vital for applying this knowledge to humans and could help bridge gaps in our understanding and treatment of mental health disorders, which often differ between sexes in both prevalence and presentation.

Single-Cell Resolution of Individual Variation in Hypothalamic Neurons Allows Targeted Manipulation Affecting Social Motivation

Despite decades of research, connecting molecular and cellular phenotypes to complex behavioral traits remains an elusive goal1. Social motivation exhibits individual trait variation2, which we hypothesize is mediated by molecular and cellular variability across hypothalamic neurons. To test this, we generated single-nucleus RNA-sequencing profiles3,4 of >120,000 neurons from tuberal hypothalamus and adjacent thalamus in 36 mice, balanced across sex and autism-associated mutation5, with all mice assessed for social motivation2. First, we show that molecular activation patterns predict behavior across individuals: specifically, activation of paraventricular Agtr1a+ (angiotensin receptor 1a) neurons predicted reduced social behavior. Subsequent inhibition of AGTR1A with telmisartan-an FDA-approved antihypertensive6-improved social orienting. Second, we show natural variation in neuronal proportions-likely arising from stochastic developmental events7-is sufficient to shape adult behavior even among genetically-identical individuals: we identified multiple neuronal populations whose relative abundance predicted social reward-seeking behavior. Chemogenetic inhibition of one such population, Nxph4+ neurons of the postero-lateral hypothalamus8, suppressed multiple aspects of social motivation. This work establishes proof-of-principle for an approach where single-cell genomics precisely maps neural substrates governing behavior. This approach revealed that stochastic variations in neuronal architecture deterministically influence social motivation, and enabled identification of therapeutically-actionable targets with immediate translational potential for disorders with social deficits.

A crucial role for the cortical amygdala in shaping social encounters

Aggression is an evolutionarily conserved behaviour that controls social hierarchies and protects valuable resources. In mice, aggressive behaviour can be broken down into an appetitive phase, which involves approach and investigation, and a consummatory phase, which involves biting, kicking and wrestling1. Here, by performing an unsupervised weighted correlation network analysis on whole-brain FOS expression in mice, we identify a cluster of brain regions, including hypothalamic and amygdalar subregions and olfactory cortical regions, that are highly co-activated in male but not in female aggressors. The posterolateral cortical amygdala (COApl)-an extended olfactory structure-was found to be a hub region, on the basis of the number and strength of correlations with other regions in the cluster. Our data also show that oestrogen receptor 1 (Esr1)-expressing cells in the COApl (COAplEsr1) exhibit increased activity during attack behaviour and during bouts of investigation that precede an attack, in male mice only. Chemogenetic or optogenetic inhibition of COAplEsr1 cells in male aggressors reduces aggression and increases pro-social investigation without affecting social reward and reinforcement behaviour. We further show that COAplEsr1 projections to the ventromedial hypothalamus and central amygdala are necessary for these behaviours. Collectively, these data suggest that, in aggressive males, COAplEsr1 cells respond specifically to social stimuli, thereby enhancing their salience and promoting attack behaviour.

Hierarchical behavioral analysis framework as a platform for standardized quantitative identification of behaviors

Behavior is composed of modules that operate based on inherent logic. Understanding behavior and its neural mechanisms is facilitated by clear structural behavioral analysis. Here, we developed a hierarchical behavioral analysis framework (HBAF) that efficiently reveals the organizational logic of these modules by analyzing high-dimensional behavioral data. By creating a spontaneous behavior atlas for male and female mice, we discovered that spontaneous behavior patterns are hardwired, with sniffing serving as the hub node for movement transitions. The sniffing-to-grooming ratio accurately distinguished the spontaneous behavioral states in a high-throughput manner. These states are influenced by emotional status, circadian rhythms, and lighting conditions, leading to unique behavioral characteristics, spatiotemporal features, and dynamic patterns. By implementing the straightforward and achievable spontaneous behavior paradigm, HBAF enables swift and accurate assessment of animal behavioral states and bridges the gap between a theoretical understanding of the behavioral structure and practical analysis using comprehensive multidimensional behavioral information.

An innate drive to save a life

In mice, two brain regions drive the impulse to revive an unconscious companion.

Rescue-like behavior in a bystander mouse toward anesthetized conspecifics promotes arousal via a tongue-brain connection

Prosocial behaviors are advantageous to social species, but the neural mechanism(s) through which others receive benefit remain unknown. Here, we found that bystander mice display rescue-like behavior (tongue dragging) toward anesthetized cagemates and found that this tongue dragging promotes arousal from anesthesia through a direct tongue-brain circuit. We found that a direct circuit from the tongue → glutamatergic neurons in the mesencephalic trigeminal nucleus (MTNGlu) → noradrenergic neurons in the locus coeruleus (LCNE) drives rapid arousal in the anesthetized mice that receive the rescue-like behavior from bystanders. Artificial inhibition of this circuit abolishes the rapid arousal effect induced by the rescue-like behavior. Further, we revealed that glutamatergic neurons in the paraventricular nucleus of the thalamus (PVTGlu) that project to the nucleus accumbens shell (NAcSh) mediate the rescue-like behavior. These findings reveal a tongue-brain connection underlying the rapid arousal effects induced by rescue-like behavior and the circuit basis governing this specific form of prosocial behavior.

Days-old zebrafish rapidly learn to recognize threatening agents through noradrenergic and forebrain circuits

Animals need to rapidly learn to recognize and avoid predators. This ability may be especially important for young animals due to their increased vulnerability. It is unknown whether, and how, nascent vertebrates are capable of such rapid learning. Here, we used a robotic predator-prey interaction assay to show that 1 week after fertilization-a developmental stage where they have approximately 1% the number of neurons of adults-zebrafish larvae rapidly and robustly learn to recognize a stationary object as a threat after the object pursues the fish for ∼1 min. Larvae continue to avoid the threatening object after it stops moving and can learn to distinguish threatening from non-threatening objects of a different color. Whole-brain functional imaging revealed the multi-timescale activity of noradrenergic neurons and forebrain circuits that encoded the threat. Chemogenetic ablation of those populations prevented the learning. Thus, a noradrenergic and forebrain multiregional network underlies the ability of young vertebrates to rapidly learn to recognize potential predators within their first week of life.

The neurobiology of parenting and infant-evoked aggression

Parenting behavior comprises a variety of adult-infant and adult-adult interactions across multiple timescales. The state transition from nonparent to parent requires an extensive reorganization of individual priorities and physiology and is facilitated by combinatorial hormone action on specific cell types that are integrated throughout interconnected and brainwide neuronal circuits. In this review, we take a comprehensive approach to integrate historical and current literature on each of these topics across multiple species, with a focus on rodents. New and emerging molecular, circuit-based, and computational technologies have recently been used to address outstanding gaps in our current framework of knowledge on infant-directed behavior. This work is raising fundamental questions about the interplay between instinctive and learned components of parenting and the mutual regulation of affiliative versus agonistic infant-directed behaviors in health and disease. Whenever possible, we point to how these technologies have helped gain novel insights and opened new avenues of research into the neurobiology of parenting. We hope this review will serve as an introduction for those new to the field, a comprehensive resource for those already studying parenting, and a guidepost for designing future studies.

The lateral thalamus: a bridge between multisensory processing and naturalistic behaviors

The lateral thalamus (LT) receives input from primary sensory nuclei and responds to multimodal stimuli. The LT is also involved in regulating innate and social behaviors through its projections to cortical and limbic networks. However, the importance of multisensory processing within the LT in modulating behavioral output has not been explicitly addressed. Here, we discuss recent findings primarily from rodent studies that extend the classical view of the LT as a passive relay, by underscoring its involvement in associating multimodal features and encoding the salience, valence, and social relevance of sensory signals. We propose that the primary function of the LT is to integrate sensory and non-sensory aspects of multisensory input to gate naturalistic behaviors.

Interconnected neural circuits mediating social reward

Across species, social behaviors are shaped and maintained through positive reinforcement of affiliative social interactions. As with nonsocial rewards, the reinforcing properties of social interactions have been shown to involve interplay between various brain regions and the mesolimbic reward system. In this review, we summarize findings from rodent research on the neural circuits that encode and mediate different components of social reward-seeking behavior. We explore methods to parse and study social reward-related behaviors using available behavioral paradigms. We also compare the neural mechanisms that support social versus nonsocial reward-seeking. Finally, we discuss how internal state and neuromodulatory systems affect reward-seeking behavior and the neural circuits that underlie social reward.

Synapse and primary cilia dysfunctions in Autism Spectrum Disorders. Avenues to normalize these functions

AIM

An update on the plasticity of the brain networks involved in autism (autism spectrum disorders [ASD]), and the increasing role of their synapses and primary non-motile cilia.

METHODS

Data from PubMed and Google on this subject, published until February 2024, were analyzed.

RESULTS

Structural and functional brain characteristics and genetic particularities involving synapses and cilia that modify neuronal circuits are observed in ASD, such as reduced pruning of dendrites, minicolumnar pathology, or persistence of connections usually doomed to disappear. Proteins involved in synapse functions (such as neuroligins and neurexins), in the postsynaptic architectural scaffolding (such as Shank proteins) or in cilia functions (such as IFT-independent kinesins) are often abnormal. There is an increase in glutaminergic transmission and a decrease in GABA inhibition. ASD may occur in genetic ciliopathies. The means of modulating these specificities, when deemed useful, are described.

INTERPRETATION

The wide range of clinical manifestations of ASD is strongly associated with abnormalities in the morphology, functions, and plasticity of brain networks, involving their synapses and non-motile cilia. Their modulation offers important research perspectives on treatments when needed, especially since brain plasticity persists much later than previously thought. Improved early detection of ASD and additional studies on synapses and primary cilia are needed.

Identification of GABAergic subpopulations in the lateral hypothalamus for home-driven behaviors in mice

Home information profoundly influences behavioral states in both humans and animals. However, how "home" is represented in the brain and its role in driving diverse related behaviors remain elusive. Here, we demonstrate that home bedding contains sufficient home information to modulate affective behaviors, including aversion responses, defensive aggression, and mating behaviors. These varied responses to home information are mediated by gama-aminobutyric acid (GABA)ergic neurons in the lateral hypothalamus (LHGABA). Inhibiting LHGABA abolishes, while activating mimics, the effects of home bedding on these behaviors across different contexts. Specifically, projections from LHGABA to the ventral tegmental area (VTA) mediate the relaxation of aversive emotion, while projections to the periaqueductal gray (PAG) initiate defensive concerns. Thus, our data suggest that home information in different contexts converges to activate distinct subgroups of the LHGABA, which, in turn, elicit appropriate affective behaviors in relieving aversion, fighting intruders, or enhancing mating through involving distinct downstream projections.

Mice lacking acid-sensing ion channel 2 in the medial prefrontal cortex exhibit social dominance

Social dominance is essential for maintaining a stable society and has both positive and negative impacts on social animals, including humans. However, the regulatory mechanisms governing social dominance, as well as the crucial regulators and biomarkers involved, remain poorly understood. We discover that mice lacking acid-sensing ion channel 2 (ASIC2) exhibit persistently higher social dominance than their wild-type cagemates. Conversely, overexpression of ASIC2 in the medial prefrontal cortex reverses the dominance hierarchy observed in ASIC2 knockout (Asic2-/-) mice. Asic2-/- neurons exhibit increased synaptic transmission and plasticity, potentially mediated by protein kinase A signaling pathway. Furthermore, ASIC2 plays distinct functional roles in excitatory and inhibitory neurons, thereby modulating the balance of neuronal activities underlying social dominance behaviors-a phenomenon suggestive of a cell subtype-specific mechanism. This research lays the groundwork for understanding the mechanisms of social dominance, offering potential insights for managing social disorders, such as depression and anxiety.

Understanding the neurobiology of social behavior through exploring brain-wide dynamics of neural activity

Social behavior is highly complex and adaptable. It can be divided into multiple temporal stages: detection, approach, and consummatory behavior. Each stage can be further divided into several cognitive and behavioral processes, such as perceiving social cues, evaluating the social and non-social contexts, and recognizing the internal/emotional state of others. Recent studies have identified numerous brain-wide circuits implicated in social behavior and suggested the existence of partially overlapping functional brain networks underlying various types of social and non-social behavior. However, understanding the brain-wide dynamics underlying social behavior remains challenging, and several brain-scale dynamics (macro-, meso-, and micro-scale levels) need to be integrated. Here, we suggest leveraging new tools and concepts to explore social brain networks and integrate those different levels. These include studying the expression of immediate-early genes throughout the entire brain to impartially define the structure of the neuronal networks involved in a given social behavior. Then, network dynamics could be investigated using electrode arrays or multi-channel fiber photometry. Finally, tools like high-density silicon probes and miniscopes can probe neural activity in specific areas and across neuronal populations at the single-cell level.

Male cuticular pheromones stimulate removal of the mating plug and promote re-mating through pC1 neurons in Drosophila females

In birds and insects, the female uptakes sperm for a specific duration post-copulation known as the ejaculate holding period (EHP) before expelling unused sperm and the mating plug through sperm ejection. In this study, we found that Drosophila melanogaster females shortens the EHP when incubated with males or mated females shortly after the first mating. This phenomenon, which we termed male-induced EHP shortening (MIES), requires Or47b+ olfactory and ppk23+ gustatory neurons, activated by 2-methyltetracosane and 7-tricosene, respectively. These odorants raise cAMP levels in pC1 neurons, responsible for processing male courtship cues and regulating female mating receptivity. Elevated cAMP levels in pC1 neurons reduce EHP and reinstate their responsiveness to male courtship cues, promoting re-mating with faster sperm ejection. This study established MIES as a genetically tractable model of sexual plasticity with a conserved neural mechanism.

The effects of different types of social interactions on the electrophysiology of neurons in the nucleus accumbens in rodents

BORLAND, J.M., The effects of different types of social interactions on the electrophysiology of neurons in the nucleus accumbens in rodents, NEUROSCI BIOBEH REV 21(1) XXX-XXX, 2024.-Sociality shapes an organisms' life. The nucleus accumbens is a critical brain region for mental health. In the following review, the effects of different types of social interactions on the physiology of neurons in the nucleus accumbens is synthesized. More specifically, the effects of sex behavior, aggression, social defeat, pair-bonding, play behavior, affiliative interactions, parental behaviors, the isolation from social interactions and maternal separation on measures of excitatory synaptic transmission, intracellular signaling and factors of transcription and translation in neurons in the nucleus accumbens in rodent models are reviewed. Similarities and differences in effects depending on the type of social interaction is then discussed. This review improves the understanding of the molecular and synaptic mechanisms of sociality.

Mapping the structure-function relationship along macroscale gradients in the human brain

Functional coactivation between human brain regions is partly explained by white matter connections; however, how the structure-function relationship varies by function remains unclear. Here, we reference large data repositories to compute maps of structure-function correspondence across hundreds of specific functions and brain regions. We use natural language processing to accurately predict structure-function correspondence for specific functions and to identify macroscale gradients across the brain that correlate with structure-function correspondence as well as cortical thickness. Our findings suggest structure-function correspondence unfolds along a sensory-fugal organizational axis, with higher correspondence in primary sensory and motor cortex for perceptual and motor functions, and lower correspondence in association cortex for cognitive functions. Our study bridges neuroscience and natural language to describe how structure-function coupling varies by region and function in the brain, offering insight into the diversity and evolution of neural network properties.

Development of neural circuits for social motion perception in schooling fish

The collective behavior of animal groups emerges from the interactions among individuals. These social interactions produce the coordinated movements of bird flocks and fish schools, but little is known about their developmental emergence and neurobiological foundations. By characterizing the visually based schooling behavior of the micro glassfish Danionella cerebrum, we found that social development progresses sequentially, with animals first acquiring the ability to aggregate, followed by postural alignment with social partners. This social maturation was accompanied by the development of neural populations in the midbrain that were preferentially driven by visual stimuli that resemble the shape and movements of schooling fish. Furthermore, social isolation over the course of development impaired both schooling behavior and the neural encoding of social motion in adults. This work demonstrates that neural populations selective for the form and motion of conspecifics emerge with the experience-dependent development of collective movement.

Medial preoptic circuits governing instinctive social behaviors

The medial preoptic area (MPOA) has long been implicated in maternal and male sexual behavior. Modern neuroscience methods have begun to reveal the cellular networks responsible, while also implicating the MPOA in other social behaviors, affiliative social touch, and aggression. The social interactions rely on input from conspecifics whose most important modalities in rodents are olfaction and somatosensation. These inputs bypass the cerebral cortex to reach the MPOA to influence the social function. Hormonal inputs also directly act on MPOA neurons. In turn, the MPOA controls social responses via various projections for reward and motor output. The MPOA thus emerges as one of the major brain centers for instinctive social behavior. While key elements of MPOA circuits have been identified, a synthesis of these new data is now provided for further studies to reveal the mechanisms by which the area controls social interactions.

Adolescent environmental enrichment induces social resilience and alters neural gene expression in a selectively bred rodent model with anxious phenotype

Stress is a major influence on mental health status; the ways that individuals respond to or copes with stressors determine whether they are negatively affected in the future. Stress responses are established by an interplay between genetics, environment, and life experiences. Psychosocial stress is particularly impactful during adolescence, a critical period for the development of mood disorders. In this study we compared two established, selectively-bred Sprague Dawley rat lines, the "internalizing" bred Low Responder (bLR) line versus the "externalizing" bred High Responder (bHR) line, to investigate how genetic temperament and adolescent environment impact future responses to social interactions and psychosocial stress, and how these determinants of stress response interact. Male bLR and bHR rats were exposed to social and environmental enrichment in adolescence prior to experiencing social defeat and were then assessed for social interaction and anxiety-like behavior. Adolescent enrichment caused rats to display more social interaction, as well as nominally less social avoidance, less submission during defeat, and resilience to the effects of social stress on corticosterone, in a manner that seemed more notable in bLRs. For bHRs, enrichment also caused greater aggression during a neutral social encounter and nominally during defeat, and decreased anxiety-like behavior. To explore the neurobiology underlying the development of social resilience in the anxious phenotype bLRs, RNA-seq was conducted on the hippocampus and nucleus accumbens, two brain regions that mediate stress regulation and social behavior. Gene sets previously associated with stress, social behavior, aggression and exploratory activity were enriched with differential expression in both regions, with a particularly large effect on gene sets that regulate social behaviors. Our findings provide further evidence that adolescent enrichment can serve as an inoculating experience against future stressors. The ability to induce social resilience in a usually anxious line of animals by manipulating their environment has translational implications, as it underscores the feasibility of intervention strategies targeted at genetically vulnerable adolescent populations.

Identifying behavioral links to neural dynamics of multifiber photometry recordings in a mouse social behavior network

Objective.Distributed hypothalamic-midbrain neural circuits help orchestrate complex behavioral responses during social interactions. Given rapid advances in optical imaging, it is a fundamental question how population-averaged neural activity measured by multi-fiber photometry (MFP) for calcium fluorescence signals correlates with social behaviors is a fundamental question. This paper aims to investigate the correspondence between MFP data and social behaviors.Approach:We propose a state-space analysis framework to characterize mouse MFP data based on dynamic latent variable models, which include a continuous-state linear dynamical system and a discrete-state hidden semi-Markov model. We validate these models on extensive MFP recordings during aggressive and mating behaviors in male-male and male-female interactions, respectively.Main results:Our results show that these models are capable of capturing both temporal behavioral structure and associated neural states, and produce interpretable latent states. Our approach is also validated in computer simulations in the presence of known ground truth.Significance:Overall, these analysis approaches provide a state-space framework to examine neural dynamics underlying social behaviors and reveals mechanistic insights into the relevant networks.

ARBUR, a machine learning-based analysis system for relating behaviors and ultrasonic vocalizations of rats

Deciphering how different behaviors and ultrasonic vocalizations (USVs) of rats interact can yield insights into the neural basis of social interaction. However, the behavior-vocalization interplay of rats remains elusive because of the challenges of relating the two communication media in complex social contexts. Here, we propose a machine learning-based analysis system (ARBUR) that can cluster without bias both non-step (continuous) and step USVs, hierarchically detect eight types of behavior of two freely behaving rats with high accuracy, and locate the vocal rat in 3-D space. ARBUR reveals that rats communicate via distinct USVs during different behaviors. Moreover, we show that ARBUR can indicate findings that are long neglected by former manual analysis, especially regarding the non-continuous USVs during easy-to-confuse social behaviors. This work could help mechanistically understand the behavior-vocalization interplay of rats and highlights the potential of machine learning algorithms in automatic animal behavioral and acoustic analysis.

A failure to discriminate social from non-social touch at the circuit level may underlie social avoidance in autism

Social touch is critical for communication and to impart emotions and intentions. However, certain autistic individuals experience aversion to social touch, especially when it is unwanted. We used a novel social touch assay and Neuropixels probes to compare neural responses to social vs. non-social interactions in three relevant brain regions: vibrissal somatosensory cortex, tail of striatum, and basolateral amygdala. We find that wild type (WT) mice showed aversion to repeated presentations of an inanimate object but not of another mouse. Cortical neurons cared most about touch context (social vs. object) and showed a preference for social interactions, while striatal neurons changed their preference depending on whether mice could choose or not to interact. Amygdalar and striatal neurons were preferentially modulated by forced object touch, which was the most aversive. In contrast, the Fmr1 knockout (KO) model of autism found social and non-social interactions equally aversive and displayed more aversive facial expressions to social touch when it invaded their personal space. Importantly, when Fmr1 KO mice could choose to interact, neurons in all three regions did not discriminate social valence. Thus, a failure to differentially encode social from non-social stimuli at the circuit level may underlie social avoidance in autism.

Neural cell-types and circuits linking thermoregulation and social behavior

Understanding how social and affective behavioral states are controlled by neural circuits is a fundamental challenge in neurobiology. Despite increasing understanding of central circuits governing prosocial and agonistic interactions, how bodily autonomic processes regulate these behaviors is less resolved. Thermoregulation is vital for maintaining homeostasis, but also associated with cognitive, physical, affective, and behavioral states. Here, we posit that adjusting body temperature may be integral to the appropriate expression of social behavior and argue that understanding neural links between behavior and thermoregulation is timely. First, changes in behavioral states-including social interaction-often accompany changes in body temperature. Second, recent work has uncovered neural populations controlling both thermoregulatory and social behavioral pathways. We identify additional neural populations that, in separate studies, control social behavior and thermoregulation, and highlight their relevance to human and animal studies. Third, dysregulation of body temperature is linked to human neuropsychiatric disorders. Although body temperature is a "hidden state" in many neurobiological studies, it likely plays an underappreciated role in regulating social and affective states.

Parenting behaviors in mice: Olfactory mechanisms and features in models of autism spectrum disorders

Rodents, along with numerous other mammals, heavily depend on olfactory cues to navigate their social interactions. Processing of olfactory sensory inputs is mediated by conserved brain circuits that ultimately trigger social behaviors, such as social interactions and parental care. Although innate, parenting is influenced by internal states, social experience, genetics, and the environment, and any significant disruption of these factors can impact the social circuits. Here, we review the molecular mechanisms and social circuits from the olfactory epithelium to central processing that initiate parental behaviors and their dysregulations that may contribute to the social impairments in mouse models of autism spectrum disorders (ASD). We discuss recent advances of the crucial role of olfaction in parental care, its consequences for social interactions, and the reciprocal influence on social interaction impairments in mouse models of ASD.

Role of neuroestrogens in the regulation of social behaviors - From social recognition to mating

In this mini-review, we summarize the brain distribution of aromatase, the enzyme catalyzing the synthesis of estrogens from androgens, and the mechanisms responsible for regulating estrogen production within the brain. Understanding this local synthesis of estrogens by neurons is pivotal as it profoundly influences various facets of social behavior. Neuroestrogen action spans from the initial processing of socially pertinent sensory cues to integrating this information with an individual's internal state, ultimately resulting in the manifestation of either pro-affiliative or - aggressive behaviors. We focus here in particular on aggressive and sexual behavior as the result of correct individual recognition of intruders and potential mates. The data summarized in this review clearly point out the crucial role of locally synthesized estrogens in facilitating rapid adaptation to the social environment in rodents and birds of both sexes. These observations not only shed light on the evolutionary significance but also indicate the potential implications of these findings in the realm of human health, suggesting a compelling avenue for further investigation.

Intrinsic Dynamics and Neural Implementation of a Hypothalamic Line Attractor Encoding an Internal Behavioral State

Line attractors are emergent population dynamics hypothesized to encode continuous variables such as head direction and internal states. In mammals, direct evidence of neural implementation of a line attractor has been hindered by the challenge of targeting perturbations to specific neurons within contributing ensembles. Estrogen receptor type 1 (Esr1)-expressing neurons in the ventrolateral subdivision of the ventromedial hypothalamus (VMHvl) show line attractor dynamics in male mice during fighting. We hypothesized that these dynamics may encode continuous variation in the intensity of an internal aggressive state. Here, we report that these neurons also show line attractor dynamics in head-fixed mice observing aggression. We exploit this finding to identify and perturb line attractor-contributing neurons using 2-photon calcium imaging and holographic optogenetic perturbations. On-manifold perturbations demonstrate that integration and persistent activity are intrinsic properties of these neurons which drive the system along the line attractor, while transient off-manifold perturbations reveal rapid relaxation back into the attractor. Furthermore, stimulation and imaging reveal selective functional connectivity among attractor-contributing neurons. Intriguingly, individual differences among mice in line attractor stability were correlated with the degree of functional connectivity among contributing neurons. Mechanistic modelling indicates that dense subnetwork connectivity and slow neurotransmission are required to explain our empirical findings. Our work bridges circuit and manifold paradigms, shedding light on the intrinsic and operational dynamics of a behaviorally relevant mammalian line attractor.

Social context modulates multibrain broadband dynamics and functional brain-to-brain coupling in the group of mice

Although mice are social, multiple animals' neural activities are rarely explored. To characterise the neural activities during multi-brain interaction, we simultaneously recorded local field potentials (LFP) in the prefrontal cortex of four mice. The social context and locomotive states predominately modulated the entire LFP structure. The power of lower frequency bands-delta to alpha-were correlated with each other and anti-correlated with gamma power. The high-to-low-power ratio (HLR) provided a useful measure to understand LFP changes along the change of behavioural and locomotive states. The HLR during huddled conditions was lower than that during non-huddled conditions, dividing the social context into two. Multi-brain analyses of HLR indicated that the mice in the group displayed high cross-correlation. The mice in the group often showed unilateral precedence of HLR by Granger causality analysis, possibly comprising a hierarchical social structure. Overall, this study shows the importance of the social environment in brain dynamics and emphasises the simultaneous multi-brain recordings in social neuroscience.

Vocal convergence and social proximity shape the calls of the most basal Passeriformes, New Zealand Wrens

Despite extensive research on avian vocal learning, we still lack a general understanding of how and when this ability evolved in birds. As the closest living relatives of the earliest Passeriformes, the New Zealand wrens (Acanthisitti) hold a key phylogenetic position for furthering our understanding of the evolution of vocal learning because they share a common ancestor with two vocal learners: oscines and parrots. However, the vocal learning abilities of New Zealand wrens remain unexplored. Here, we test for the presence of prerequisite behaviors for vocal learning in one of the two extant species of New Zealand wrens, the rifleman (Acanthisitta chloris). We detect the presence of unique individual vocal signatures and show how these signatures are shaped by social proximity, as demonstrated by group vocal signatures and strong acoustic similarities among distantly related individuals in close social proximity. Further, we reveal that rifleman calls share similar phenotypic variance ratios to those previously reported in the learned vocalizations of the zebra finch, Taeniopygia guttata. Together these findings provide strong evidence that riflemen vocally converge, and though the mechanism still remains to be determined, they may also suggest that this vocal convergence is the result of rudimentary vocal learning abilities.

The basal forebrain to lateral habenula circuitry mediates social behavioral maladaptation

Elucidating the neural basis of fear allows for more effective treatments for maladaptive fear often observed in psychiatric disorders. Although the basal forebrain (BF) has an essential role in fear learning, its function in fear expression and the underlying neuronal and circuit substrates are much less understood. Here we report that BF glutamatergic neurons are robustly activated by social stimulus following social fear conditioning in male mice. And cell-type-specific inhibition of those excitatory neurons largely reduces social fear expression. At the circuit level, BF glutamatergic neurons make functional contacts with the lateral habenula (LHb) neurons and these connections are potentiated in conditioned mice. Moreover, optogenetic inhibition of BF-LHb glutamatergic pathway significantly reduces social fear responses. These data unravel an important function of the BF in fear expression via its glutamatergic projection onto the LHb, and suggest that selective targeting BF-LHb excitatory circuitry could alleviate maladaptive fear in relevant disorders.

From Parental Behavior to Sexual Function: Recent Advances in Oxytocin Research

Purpose of Review

Oxytocin plays many diverse roles in physiological and behavioral processes, including social activity, parental nurturing, stress responses, and sexual function. In this narrative review, we provide an update on the most noteworthy recent findings in this fascinating field.

Recent Findings

The development of techniques such as serial two-photon tomography and fiber photometry have provided a window into oxytocin neuroanatomy and real-time neuronal activity during social interactions. fMRI and complementary mapping techniques offer new insights into oxytocin's influence on brain activity and connectivity. Indeed, oxytocin has recently been found to influence the acquisition of maternal care behaviors and to mediate the influence of social touch on brain development and social interaction. Additionally, oxytocin plays a crucial role in male sexual function, affecting erectile activity and ejaculation, while its role in females remains controversial. Recent studies also highlight oxytocin's interaction with other neuropeptides, such as melanin-concentrating hormone, serotonin, and arginine vasopressin, influencing social and affective behaviors. Finally, an update is provided on the status of clinical trials involving oxytocin as a therapeutic intervention.

Summary

The exploration of oxytocin's complexities and its interplay with other neuropeptides holds promise for targeted treatment in various health and disease contexts. Overall, these findings contribute to the discovery of new and specific pathways to allow therapeutic targeting of oxytocin to treat disorders.

Sexually dimorphic control of affective state processing and empathic behaviors

Recognizing the affective states of social counterparts and responding appropriately fosters successful social interactions. However, little is known about how the affective states are expressed and perceived and how they influence social decisions. Here, we show that male and female mice emit distinct olfactory cues after experiencing distress. These cues activate distinct neural circuits in the piriform cortex (PiC) and evoke sexually dimorphic empathic behaviors in observers. Specifically, the PiC → PrL pathway is activated in female observers, inducing a social preference for the distressed counterpart. Conversely, the PiC → MeA pathway is activated in male observers, evoking excessive self-grooming behaviors. These pathways originate from non-overlapping PiC neuron populations with distinct gene expression signatures regulated by transcription factors and sex hormones. Our study unveils how internal states of social counterparts are processed through sexually dimorphic mechanisms at the molecular, cellular, and circuit levels and offers insights into the neural mechanisms underpinning sex differences in higher brain functions.

Adolescent environmental enrichment induces social resilience and alters neural gene expression in a selectively bred rodent model with anxious phenotype

Stress is a major influence on mental health status; the ways that individuals respond to or copes with stressors determine whether they are negatively affected in the future. Stress responses are established by an interplay between genetics, environment, and life experiences. Psychosocial stress is particularly impactful during adolescence, a critical period for the development of mood disorders. In this study we compared two established, selectively-bred Sprague Dawley rat lines, the "internalizing" bred Low Responder (bLR) line versus the "externalizing" bred High Responder (bHR) line, to investigate how genetic temperament and adolescent environment impact future responses to social interactions and psychosocial stress, and how these determinants of stress response interact. Male bLR and bHR rats were exposed to social and environmental enrichment in adolescence prior to experiencing social defeat and were then assessed for social interaction and anxiety-like behavior. Adolescent enrichment caused rats to display more social interaction, as well as nominally less social avoidance, less submission during defeat, and resilience to the effects of social stress on corticosterone, in a manner that seemed more notable in bLRs. For bHRs, enrichment also caused greater aggression during a neutral social encounter and nominally during defeat, and decreased anxiety-like behavior. To explore the neurobiology underlying the development of social resilience in the anxious phenotype bLRs, RNA-seq was conducted on the hippocampus and nucleus accumbens, two brain regions that mediate stress regulation and social behavior. Gene sets previously associated with stress, social behavior, aggression and exploratory activity were enriched with differential expression in both regions, with a particularly large effect on gene sets that regulate social behaviors. Our findings provide further evidence that adolescent enrichment can serve as an inoculating experience against future stressors. The ability to induce social resilience in a usually anxious line of animals by manipulating their environment has translational implications, as it underscores the feasibility of intervention strategies targeted at genetically vulnerable adolescent populations.

NRG1-ErbB4 signaling in the medial amygdala controls mating motivation in adult male mice

Motivation-driven mating is a basic affair for the maintenance of species. However, the underlying molecular mechanisms that control mating motivation are not fully understood. Here, we report that NRG1-ErbB4 signaling in the medial amygdala (MeA) is pivotal in regulating mating motivation. NRG1 expression in the MeA negatively correlates with the mating motivation levels in adult male mice. Local injection and knockdown of MeA NRG1 reduce and promote mating motivation, respectively. Consistently, knockdown of MeA ErbB4, a major receptor for NRG1, and genetic inactivation of its kinase both promote mating motivation. ErbB4 deletion decreases neuronal excitability, whereas chemogenetic manipulations of ErbB4-positive neuronal activities bidirectionally modulate mating motivation. We also identify that the effects of NRG1-ErbB4 signaling on neuronal excitability and mating motivation rely on hyperpolarization-activated cyclic nucleotide-gated channel 3. This study reveals a critical molecular mechanism for regulating mating motivation in adult male mice.

A neural pathway for social modulation of spontaneous locomotor activity (SoMo-SLA) in Drosophila

Social enrichment or social isolation affects a range of innate behaviors, such as sex, aggression, and sleep, but whether there is a shared mechanism is not clear. Here, we report a neural mechanism underlying social modulation of spontaneous locomotor activity (SoMo-SLA), an internal-driven behavior indicative of internal states. We find that social enrichment specifically reduces spontaneous locomotor activity in male flies. We identify neuropeptides Diuretic hormone 44 (DH44) and Tachykinin (TK) to be up- and down-regulated by social enrichment and necessary for SoMo-SLA. We further demonstrate a sexually dimorphic neural circuit, in which the male-specific P1 neurons encoding internal states form positive feedback with interneurons coexpressing doublesex (dsx) and Tk to promote locomotion, while P1 neurons also form negative feedback with interneurons coexpressing dsx and DH44 to inhibit locomotion. These two opposing neuromodulatory recurrent circuits represent a potentially common mechanism that underlies the social regulation of multiple innate behaviors.

Identifying behavioral links to neural dynamics of multifiber photometry recordings in a mouse social behavior network

Distributed hypothalamic-midbrain neural circuits orchestrate complex behavioral responses during social interactions. How population-averaged neural activity measured by multi-fiber photometry (MFP) for calcium fluorescence signals correlates with social behaviors is a fundamental question. We propose a state-space analysis framework to characterize mouse MFP data based on dynamic latent variable models, which include continuous-state linear dynamical system (LDS) and discrete-state hidden semi-Markov model (HSMM). We validate these models on extensive MFP recordings during aggressive and mating behaviors in male-male and male-female interactions, respectively. Our results show that these models are capable of capturing both temporal behavioral structure and associated neural states. Overall, these analysis approaches provide an unbiased strategy to examine neural dynamics underlying social behaviors and reveals mechanistic insights into the relevant networks.

Synchronized LFP rhythmicity in the social brain reflects the context of social encounters

Mammalian social behavior is highly context-sensitive. Yet, little is known about the mechanisms that modulate social behavior according to its context. Recent studies have revealed a network of mostly limbic brain regions which regulates social behavior. We hypothesize that coherent theta and gamma rhythms reflect the organization of this network into functional sub-networks in a context-dependent manner. To test this concept, we simultaneously record local field potential (LFP) from multiple social brain regions in adult male mice performing three social discrimination tasks. While LFP rhythmicity across all tasks is dominated by a global internal state, the pattern of theta coherence between the various regions reflect the behavioral task more than other variables. Moreover, Granger causality analysis implicate the ventral dentate gyrus as a main player in coordinating the context-specific rhythmic activity. Thus, our results suggest that the pattern of coordinated rhythmic activity within the network reflects the subject's social context.

Disruption of Cdk5-GluN2B complex by a small interfering peptide attenuates social isolation-induced escalated intermale attack behavior and hippocampal oxidative stress in mice

Social isolation has emerged as a significant issue during the COVID-19 pandemic that can adversely impact human mental health and potentially lead to pathological aggression. Given the lack of effective therapeutic interventions for aggressive behavior, alternative approaches are necessary. In this study, we utilized a genetic method combined with a pharmacological approach to identify and demonstrate the crucial role of Cdk5 in escalated intermale attack behavior induced by 2-week social isolation. Moreover, we developed a small peptide that effectively disrupts the interaction between Cdk5 and GluN2B, given the known involvement of this complex in various neuropsychiatric disorders. Administration of the peptide, either systemically or via intrahippocampal injection, significantly reduced oxidative stress in the hippocampus and attenuated intermale attack behavior induced by 2-week social isolation. These findings highlight the previously unknown role of the hippocampal Cdk5-GluN2B complex in social isolation-induced aggressive behavior in mice and propose the peptide as a promising therapeutic strategy for regulating attack behavior and oxidative stress.

Transcriptionally defined amygdala subpopulations play distinct roles in innate social behaviors

Social behaviors are innate and supported by dedicated neural circuits, but the molecular identities of these circuits and how they are established developmentally and shaped by experience remain unclear. Here we show that medial amygdala (MeA) cells originating from two embryonically parcellated developmental lineages have distinct response patterns and functions in social behavior in male mice. MeA cells expressing the transcription factor Foxp2 (MeAFoxp2) are specialized for processing male conspecific cues and are essential for adult inter-male aggression. By contrast, MeA cells derived from the Dbx1 lineage (MeADbx1) respond broadly to social cues, respond strongly during ejaculation and are not essential for male aggression. Furthermore, MeAFoxp2 and MeADbx1 cells show differential anatomical and functional connectivity. Altogether, our results suggest a developmentally hardwired aggression circuit at the MeA level and a lineage-based circuit organization by which a cell's embryonic transcription factor profile determines its social information representation and behavioral relevance during adulthood.