two-color-multifiber-photometry-recordings-social-behavior-network

Two-color Multifiber Photometry Recordings of the Social Behavior Network in Mice

Fiber photometry, the bulk recording of signals through a fiber optic cable, is a useful method for recording calcium activity from groups of neurons in ...

Princeton University

Transgender rights rely on inclusive language.

While aggression is often conceptualized as a highly stereotyped, innate behavior, individuals within a species exhibit a surprising amount of variability in the frequency, intensity, and targets of their aggression. While differences in genetics are a source of some of this variation across individuals (estimates place the heritability of behavior at around 25-30%), a critical driver of variability is previous life experience. A wide variety of social experiences, including sexual, parental, and housing experiences can facilitate "persistent" aggressive states, suggesting that these experiences engage a common set of synaptic and molecular mechanisms that act on dedicated neural circuits for aggression. It has long been known that sex steroid hormones are powerful modulators of behavior, and also, that levels of these hormones are themselves modulated by experience. Several recent studies have started to unravel how experience-dependent hormonal changes during adulthood can create a cascade of molecular, synaptic, and circuit changes that enable behavioral persistence through circuit level remodeling. Here, we propose that sex steroid hormones facilitate persistent aggressive states by changing the relationship between neural activity and an aggression "threshold".

Neural mechanisms of persistent aggression.

Most studies attempting to address the health care needs of the millions of transgender, nonbinary, and/or gender-diverse (TNG) individuals rely on human subjects, overlooking the benefits of translational research in animal models. Researchers have identified many ways in which gonadal steroid hormones regulate neuronal gene expression, connectivity, activity, and function across the brain to control behavior. However, these discoveries primarily benefit cisgender populations. Research into the effects of exogenous hormones such as estradiol, testosterone, and progesterone has a direct translational benefit for TNG individuals on gender-affirming hormone therapies (GAHTs). Despite this potential, endocrinological health care for TNG individuals remains largely unimproved. Here, we outline important areas of translational research that could address the unique health care needs of TNG individuals on GAHT. We highlight key biomedical questions regarding GAHT that can be investigated using animal models. We discuss how contemporary research fails to address the needs of GAHT users and identify equitable practices for cisgender scientists engaging with this work. We conclude that if necessary and important steps are taken to address these issues, translational research on GAHTs will greatly benefit the health care outcomes of TNG people.

Centering the Needs of Transgender, Nonbinary, and Gender-Diverse Populations in Neuroendocrine Models of Gender-Affirming Hormone Therapy.

Animals learn the value of foods based on their postingestive effects and thereby develop aversions to foods that are toxic and preferences to those that are nutritious. However, it remains unclear how the brain is able to assign credit to flavors experienced during a meal with postingestive feedback signals that can arise after a substantial delay. Here, we reveal an unexpected role for postingestive reactivation of neural flavor representations in this temporal credit assignment process. To begin, we leverage the fact that mice learn to associate novel, but not familiar, flavors with delayed gastric malaise signals to investigate how the brain represents flavors that support aversive postingestive learning. Surveying cellular resolution brainwide activation patterns reveals that a network of amygdala regions is unique in being preferentially activated by novel flavors across every stage of the learning process: the initial meal, delayed malaise, and memory retrieval. By combining high-density recordings in the amygdala with optogenetic stimulation of genetically defined hindbrain malaise cells, we find that postingestive malaise signals potently and specifically reactivate amygdalar novel flavor representations from a recent meal. The degree of malaise-driven reactivation of individual neurons predicts strengthening of flavor responses upon memory retrieval, leading to stabilization of the population-level representation of the recently consumed flavor. In contrast, meals without postingestive consequences degrade neural flavor representations as flavors become familiar and safe. Thus, our findings demonstrate that interoceptive reactivation of amygdalar flavor representations provides a neural mechanism to resolve the temporal credit assignment problem inherent to postingestive learning.

A neural mechanism for learning from delayed postingestive feedback.

We have recently proposed experimental design guidelines and areas of study for preclinical rodent models of gender-affirming hormone therapy in neuroscience. These guidelines also apply to any field subject to the influences of gonadal steroid hormones, including metabolism and growth, cancer, and physiology. This perspective briefly describes our suggestions for these fields. Studying the effects of exogenous steroid hormones will have translational benefits for the community. We also discuss the need for equitable practices for cisgender scientists who wish to implement these guidelines and engage with the community. It is necessary that community-informed practices are implemented in preclinical research to maximize the benefit to transgender, nonbinary, and/or gender diverse (TNG) healthcare, which is currently in jeopardy in the United States, Europe, and across the globe.

Using Animal Models for Gender-Affirming Hormone Therapy.

To build a just, equitable, and diverse academy, scientists and institutions must address systemic barriers that sex and gender minorities face. This Commentary summarizes (1) critical context informing the contemporary oppression of transgender people, (2) how this shapes extant research on sex and gender, and (3) actions to build an inclusive and rigorous academy for all.

Rigorous science demands support of transgender scientists.

The ability to observe the social behavior of others and use observed information to bias future action is a fundamental building block of social cognition. A foundational question is whether social observation and experience engage common circuit mechanisms that enable behavioral change. While classic studies on social learning have shown that aggressive behaviors can be learned through observation, it remains unclear whether aggression observation promotes persistent neural changes that generalize to new contexts. Here, to directly compare the effects of aggression experience and observation at brain-wide scale, we develop a strategy to perform large-scale cell-type specific recordings across subcortical networks for social behavior control and learning. We record longitudinally while animals "train" through direct experience or observation, then probe shared differences in behavior and neural activity in a novel "hard" aggression context. Using supervised and unsupervised methods for behavioral quantification, we detect unique signatures of a shared behavioral strategy not present in animals with no training. During observation, we find widespread activation that mimics experience in networks for behavior generation, with critical differences in signals associated with reward and threat learning. After observation, we observe that changes persist into the novel aggression context, with increased similarity in the neural dynamics between experience and observation groups. Network-level modeling reveals persistent shared changes to a core aggression network, with widespread decoupling of inhibition from a key hypothalamic output region. This demonstrates that "experience-like" activity during observation can recruit a shared plasticity mechanism that biases behavior toward adaptive defensive strategies in new contexts.

Aggression experience and observation promote shared behavioral and neural changes.

Animals learn the value of foods on the basis of their postingestive effects and thereby develop aversions to foods that are toxic and preferences to those that are nutritious. However, it remains unclear how the brain is able to assign credit to flavours experienced during a meal with postingestive feedback signals that can arise after a substantial delay. Here we reveal an unexpected role for the postingestive reactivation of neural flavour representations in this temporal credit-assignment process. To begin, we leverage the fact that mice learn to associate novel, but not familiar, flavours with delayed gastrointestinal malaise signals to investigate how the brain represents flavours that support aversive postingestive learning. Analyses of brain-wide activation patterns reveal that a network of amygdala regions is unique in being preferentially activated by novel flavours across every stage of learning (consumption, delayed malaise and memory retrieval). By combining high-density recordings in the amygdala with optogenetic stimulation of malaise-coding hindbrain neurons, we show that delayed malaise signals selectively reactivate flavour representations in the amygdala from a recent meal. The degree of malaise-driven reactivation of individual neurons predicts the strengthening of flavour responses upon memory retrieval, which in turn leads to stabilization of the population-level representation of the recently consumed flavour. By contrast, flavour representations in the amygdala degrade in the absence of unexpected postingestive consequences. Thus, we demonstrate that postingestive reactivation and plasticity of neural flavour representations may support learning from delayed feedback.

Deciding whether and when to engage in social interaction depends on external factors including the location of the interaction and the identity of the social partner (the social "context") as well as internal factors such as an individual's hormonal state. However, we lack a mechanistic understanding of how external and internal variables coordinate social action through networks of hormone-sensitive neurons. In particular, while gonadal hormones have long been suggested to coordinate territorial behaviors, direct evidence of how this coordination occurs has been lacking. To answer this, we combined large-scale neural recordings with large-scale unsupervised behavioral quantification to track neural activity longitudinally across a hormonal perturbation. We recorded neural population activity from neurons expressing the hormone receptor estrogen receptor alpha (ERɑ+) as well as from local ERɑ- neurons across the subcortical Social Behavior Network (SBN) and compared neural responses and behavior across social contexts with varied partners and territories. Using a comprehensive behavioral quantification strategy, we observe that patterns of social action and their underlying neural dynamics differentiate social partner and territory in both sexes. We find that each context has a unique behavioral action code, and that territory naturally rescales the partner-specific social action code in the hormonally intact state. However, when levels of circulating gonadal hormones are reduced, we observe that patterns of behavior during interactions in the home territory in males are disrupted, and that these changes can be rescued by testosterone replacement. Critically, hormonal perturbation disrupts territorial rescaling in a population-specific manner. Together, these data demonstrate how a loss of circulating hormones alters the relationship between social context and social action to disrupt context-specific social decision making.

Context rescales a social action code in a hormone-sensitive network.

Estrogens are inherently dynamic signaling molecules whose fluctuations induce profound shifts in physiology and behavior. However, methods for tracking the dynamics of estrogen action  are limited and not tissue-specific, making it difficult to directly relate dynamics to ongoing physiological, behavioral, and neural changes. Traditionally, estrogen sensitive cells have been identified by metrics such as receptor expression or radioactive ligand binding, but these measures do not capture the dynamic nature of hormone response. In addition, current methods for assessing the dynamics of estrogens in an individual, including microdialysis and vaginal cytology, lack temporal and spatial resolution. To address this need we developed a bifunctional reporter called neuro-seeER (neuronal see Estrogen Response) that can be used to track changes in exogenous and endogenous estrogen dynamics  and  including longitudinally in behaving animals. We confirmed that the fluorescent response requires estrogen receptor expression, is specific to activation with estradiol, and is consistent with the timescale of transcriptional induction. Neuro-seeER expression in the hypothalamus of Esr1-Cre mice revealed dynamic labeling of estrogen-responsive cells following treatment with exogenous estradiol, and fluorescence-aided cell sorting followed by RNA-sequencing confirmed that high neuro-seeER response is associated with enriched expression of genes associated with endogenous estrogen responses. Using a novel "snapshot" photometry method to track the dynamics longitudinally  we demonstrate that we can robustly detect exogenous estrogen response across multiple hypothalamic sites simultaneously. Finally, we demonstrate that this tool is uniquely suited to capturing endogenous estrogen response dynamics  across the long timescale of the estrous cycle, revealing individual differences in neural estrogen dynamics. Together, these findings reveal unexpected cellular and temporal heterogeneity of the transcriptional response and demonstrate the feasibility of tracking the dynamics of hormonal response alongside additional neural, cell signaling, or behavioral measures.

Article	Year
Transgender rights rely on inclusive language. Science (New York, N.Y.)\| PubMed ID: 34941389	2021
Neural mechanisms of persistent aggression. Current opinion in neurobiology\| PubMed ID: 35344844	2022
Centering the Needs of Transgender, Nonbinary, and Gender-Diverse Populations in Neuroendocrine Models of Gender-Affirming Hormone Therapy. Biological psychiatry. Cognitive neuroscience and neuroimaging\| PubMed ID: 35863692	2022
A neural mechanism for learning from delayed postingestive feedback. bioRxiv : the preprint server for biology\| PubMed ID: 37873112	2024
Using Animal Models for Gender-Affirming Hormone Therapy. Journal of the Endocrine Society\| PubMed ID: 38090229	2023
Rigorous science demands support of transgender scientists. Cell\| PubMed ID: 38490174	2024
Aggression experience and observation promote shared behavioral and neural changes. bioRxiv : the preprint server for biology\| PubMed ID: 39763843	2024
A neural mechanism for learning from delayed postingestive feedback. Nature\| PubMed ID: 40175547	2025
Context rescales a social action code in a hormone-sensitive network. bioRxiv : the preprint server for biology\| PubMed ID: 41040254	2025
A bifunctional optical reporter for tracking estrogen response dynamics in neurons. bioRxiv : the preprint server for biology\| PubMed ID: 41427375	2025

Eartha Mae Guthman

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