Loss of Intercalated Cells (ITCs) in the Mouse Amygdala of Tshz1 Mutants Correlates with Fear, Depression, and Social Interaction Phenotypes

Psychedelic control of neuroimmune interactions governing fear

Neuroimmune interactions-signals transmitted between immune and brain cells-regulate many aspects of tissue physiology1, including responses to psychological stress2-5, which can predispose individuals to develop neuropsychiatric diseases6-9. Still, the interactions between haematopoietic and brain-resident cells that influence complex behaviours are poorly understood. Here, we use a combination of genomic and behavioural screens to show that astrocytes in the amygdala limit stress-induced fear behaviour through epidermal growth factor receptor (EGFR). Mechanistically, EGFR expression in amygdala astrocytes inhibits a stress-induced, pro-inflammatory signal-transduction cascade that facilitates neuron-glial crosstalk and stress-induced fear behaviour through the orphan nuclear receptor NR2F2 in amygdala neurons. In turn, decreased EGFR signalling and fear behaviour are associated with the recruitment of meningeal monocytes during chronic stress. This set of neuroimmune interactions is therapeutically targetable through the administration of psychedelic compounds, which reversed the accumulation of monocytes in the brain meninges along with fear behaviour. Together with validation in clinical samples, these data suggest that psychedelics can be used to target neuroimmune interactions relevant to neuropsychiatric disorders and potentially other inflammatory diseases.

High order expression dependencies finely resolve cryptic states and subtypes in single cell data

Single cells are typically typed by clustering into discrete locations in reduced dimensional transcriptome space. Here we introduce Stator, a data-driven method that identifies cell (sub)types and states without relying on cells' local proximity in transcriptome space. Stator labels the same single cell multiply, not just by type and subtype, but also by state such as activation, maturity or cell cycle sub-phase, through deriving higher-order gene expression dependencies from a sparse gene-by-cell expression matrix. Stator's finer resolution is clear from analyses of mouse embryonic brain, and human healthy or diseased liver. Rather than only coarse-scale labels of cell type, Stator further resolves cell types into subtypes, and these subtypes into stages of maturity and/or cell cycle phases, and yet further into portions of these phases. Among cryptically homogeneous embryonic cells, for example, Stator finds 34 distinct radial glia states whose gene expression forecasts their future GABAergic or glutamatergic neuronal fate. Further, Stator's fine resolution of liver cancer states reveals expression programmes that predict patient survival. We provide Stator as a Nextflow pipeline and Shiny App.

Modelling a pathological GSX2 variant that selectively alters DNA binding reveals hypomorphic mouse brain defects

Gsx2 is a homeodomain transcription factor critical for development of the ventral telencephalon and hindbrain in mouse. Loss of Gsx2 function results in severe basal ganglia dysgenesis and defects in the nucleus tractus solitarius (nTS) of the hindbrain, together with respiratory failure at birth. De Mori et al. (2019) reported two patients with severe dystonia and basal ganglia dysgenesis that encode distinct recessive GSX2 variants, including a missense variant within the homeodomain (GSX2Q251R). Hence, we modelled the homologous Gsx2 mutation (i.e. Gsx2Q252R) in mouse, and our biochemical analysis revealed that this variant selectively altered DNA binding. Moreover, mice carrying the Gsx2Q252R allele exhibited basal ganglia dysgenesis, albeit to a lesser extent than did Gsx2 null mice. A notable difference between Gsx2Q252R and Gsx2 null mice was that Gsx2Q252R mice survived, and hindbrain analysis revealed relative sparing of the glutamatergic nTS neurons and catecholaminergic A1/C1 and A2/C2 groups. Thus, the Gsx2Q252R variant is a hypomorph that compromises a subset of Gsx2-dependent neuronal subtypes and highlights a critical role for distinct thresholds of catecholaminergic and/or glutamatergic nTS neurons for viability.

Amygdala intercalated cells form an evolutionarily conserved system orchestrating brain networks

The amygdala attributes valence and emotional salience to environmental stimuli and regulates how these stimuli affect behavior. Within the amygdala, a distinct class of evolutionarily conserved neurons form the intercalated cell (ITC) clusters, mainly located around the boundaries of the lateral and basal nuclei. Here, we review the anatomical, physiological and molecular characteristics of ITCs, and detail the organization of ITC clusters and their connectivity with one another and other brain regions. We describe how ITCs undergo experience-dependent plasticity and discuss emerging evidence demonstrating how ITCs are innervated and functionally regulated by neuromodulatory systems. We summarize recent findings showing that experience alters the balance of activity between different ITC clusters, thereby determining prevailing behavioral output. Finally, we propose a model in which ITCs form a key system for integrating divergent inputs and orchestrating brain-wide circuits to generate behavioral states attuned to current environmental circumstances and internal needs.

Translational Insights From Cell Type Variation Across Amygdala Subnuclei in Rhesus Monkeys and Humans

OBJECTIVE

Theories of amygdala function are central to our understanding of psychiatric and neurodevelopmental disorders. However, limited knowledge of the molecular and cellular composition of the amygdala impedes translational research aimed at developing new treatments and interventions. The aim of this study was to characterize and compare the composition of amygdala cells to help bridge the gap between preclinical models and human psychiatric and neurodevelopmental disorders.

METHODS

Tissue was dissected from multiple amygdala subnuclei in both humans (N=3, male) and rhesus macaques (N=3, male). Single-nucleus RNA sequencing was performed to characterize the transcriptomes of individual nuclei.

RESULTS

The results reveal substantial heterogeneity between regions, even when restricted to inhibitory or excitatory neurons. Consistent with previous work, the data highlight the complexities of individual marker genes for uniquely targeting specific cell types. Cross-species analyses suggest that the rhesus monkey model is well-suited to understanding the human amygdala, but also identify limitations. For example, a cell cluster in the ventral lateral nucleus of the amygdala (vLa) is enriched in humans relative to rhesus macaques. Additionally, the data describe specific cell clusters with relative enrichment of disorder-related genes. These analyses point to the human-enriched vLa cell cluster as relevant to autism spectrum disorder, potentially highlighting a vulnerability to neurodevelopmental disorders that has emerged in recent primate evolution. Further, a cluster of cells expressing markers for intercalated cells is enriched for genes reported in human genome-wide association studies of neuroticism, anxiety disorders, and depressive disorders.

CONCLUSIONS

Together, these findings shed light on the composition of the amygdala and identify specific cell types that can be prioritized in basic science research to better understand human psychopathology and guide the development of potential treatments.

Genetically- and spatially-defined basolateral amygdala neurons control food consumption and social interaction

The basolateral amygdala (BLA) contains discrete neuronal circuits that integrate positive or negative emotional information and drive the appropriate innate and learned behaviors. Whether these circuits consist of genetically-identifiable and anatomically segregated neuron types, is poorly understood. Also, our understanding of the response patterns and behavioral spectra of genetically-identifiable BLA neurons is limited. Here, we classified 11 glutamatergic cell clusters in mouse BLA and found that several of them were anatomically segregated in lateral versus basal amygdala, and anterior versus posterior regions of the BLA. Two of these BLA subpopulations innately responded to valence-specific, whereas one responded to mixed - aversive and social - cues. Positive-valence BLA neurons promoted normal feeding, while mixed selectivity neurons promoted fear learning and social interactions. These findings enhance our understanding of cell type diversity and spatial organization of the BLA and the role of distinct BLA populations in representing valence-specific and mixed stimuli.

The transcriptomic and spatial organization of telencephalic GABAergic neuronal types

The telencephalon of the mammalian brain comprises multiple regions and circuit pathways that play adaptive and integrative roles in a variety of brain functions. There is a wide array of GABAergic neurons in the telencephalon; they play a multitude of circuit functions, and dysfunction of these neurons has been implicated in diverse brain disorders. In this study, we conducted a systematic and in-depth analysis of the transcriptomic and spatial organization of GABAergic neuronal types in all regions of the mouse telencephalon and their developmental origins. This was accomplished by utilizing 611,423 single-cell transcriptomes from the comprehensive and high-resolution transcriptomic and spatial cell type atlas for the adult whole mouse brain we have generated, supplemented with an additional single-cell RNA-sequencing dataset containing 99,438 high-quality single-cell transcriptomes collected from the pre- and postnatal developing mouse brain. We present a hierarchically organized adult telencephalic GABAergic neuronal cell type taxonomy of 7 classes, 52 subclasses, 284 supertypes, and 1,051 clusters, as well as a corresponding developmental taxonomy of 450 clusters across different ages. Detailed charting efforts reveal extraordinary complexity where relationships among cell types reflect both spatial locations and developmental origins. Transcriptomically and developmentally related cell types can often be found in distant and diverse brain regions indicating that long-distance migration and dispersion is a common characteristic of nearly all classes of telencephalic GABAergic neurons. Additionally, we find various spatial dimensions of both discrete and continuous variations among related cell types that are correlated with gene expression gradients. Lastly, we find that cortical, striatal and some pallidal GABAergic neurons undergo extensive postnatal diversification, whereas septal and most pallidal GABAergic neuronal types emerge simultaneously during the embryonic stage with limited postnatal diversification. Overall, the telencephalic GABAergic cell type taxonomy can serve as a foundational reference for molecular, structural and functional studies of cell types and circuits by the entire community.

Foxp2 deficiency impairs reproduction by modulating the hypothalamic-pituitary-gonadal axis in zebrafish†

FOXP2 was initially characterized as a transcription factor linked to speech and language disorders. Single-cell RNA sequencing reveals that Foxp2 is enriched in the gonadotrope cluster of the pituitary gland and colocalized with the hormones LHB and FSHB in chickens and mice, implying that FOXP2 might be associated with reproduction in vertebrates. Herein, we investigated the roles of foxp2 in reproduction in a Foxp2-deficient zebrafish model. The results indicated that the loss of Foxp2 inhibits courtship behavior in adult male zebrafish. Notably, Foxp2 deficiency disrupts gonad development, leading to retardation of follicle development and a decrease in oocytes in females at the full-growth stage, among other phenotypes. The transcriptome analysis (RNA-seq) also revealed that differentially expressed genes clustered into the estrogen signaling and ovarian steroidogenesis-related signaling pathways. In addition, we found that Foxp2 deficiency could modulate the hypothalamic-pituitary-gonadal axis, especially the regulation of lhb and fshb expression, in zebrafish. In contrast, the injection of human chorionic gonadotropin, a specific LH agonist, partially rescues Foxp2-impaired reproduction in zebrafish, suggesting that Foxp2 plays an important role in the regulation of reproduction via the hypothalamic-pituitary-gonadal axis in zebrafish. Thus, our findings reveal a new role for Foxp2 in the regulation of reproduction in vertebrates.

Delayed maturation and migration of excitatory neurons in the juvenile mouse paralaminar amygdala

The human amygdala paralaminar nucleus (PL) contains many immature excitatory neurons that undergo prolonged maturation from birth to adulthood. We describe a previously unidentified homologous PL region in mice that contains immature excitatory neurons and has previously been considered part of the amygdala intercalated cell clusters or ventral endopiriform cortex. Mouse PL neurons are born embryonically, not from postnatal neurogenesis, despite a subset retaining immature molecular and morphological features in adults. During juvenile-adolescent ages (P21-P35), the majority of PL neurons undergo molecular, structural, and physiological maturation, and a subset of excitatory PL neurons migrate into the adjacent endopiriform cortex. Alongside these changes, PL neurons develop responses to aversive and appetitive olfactory stimuli. The presence of this homologous region in both humans and mice points to the significance of this conserved mechanism of neuronal maturation and migration during adolescence, a key time period for amygdala circuit maturation and related behavioral changes.

Baf-mediated transcriptional regulation of teashirt is essential for the development of neural progenitor cell lineages

Accumulating evidence hints heterochromatin anchoring to the inner nuclear membrane as an upstream regulatory process of gene expression. Given that the formation of neural progenitor cell lineages and the subsequent maintenance of postmitotic neuronal cell identity critically rely on transcriptional regulation, it seems possible that the development of neuronal cells is influenced by cell type-specific and/or context-dependent programmed regulation of heterochromatin anchoring. Here, we explored this possibility by genetically disrupting the evolutionarily conserved barrier-to-autointegration factor (Baf) in the Drosophila nervous system. Through single-cell RNA sequencing, we demonstrated that Baf knockdown induces prominent transcriptomic changes, particularly in type I neuroblasts. Among the differentially expressed genes, our genetic analyses identified teashirt (tsh), a transcription factor that interacts with beta-catenin, to be closely associated with Baf knockdown-induced phenotypes that were suppressed by the overexpression of tsh or beta-catenin. We also found that Baf and tsh colocalized in a region adjacent to heterochromatin in type I NBs. Notably, the subnuclear localization pattern remained unchanged when one of these two proteins was knocked down, indicating that both proteins contribute to the anchoring of heterochromatin to the inner nuclear membrane. Overall, this study reveals that the Baf-mediated transcriptional regulation of teashirt is a novel molecular mechanism that regulates the development of neural progenitor cell lineages.

Developmental origin of the mammalian premaxilla

The evolution of jaws has played a major role in the success of vertebrate expansion into a wide variety of ecological niches. A fundamental, yet unresolved, question in craniofacial biology is about the origin of the premaxilla, the most distal bone present in the upper jaw of all amniotes. Recent reports have suggested that the mammalian premaxilla is derived from embryonic maxillary prominences rather than the frontonasal ectomesenchyme as previously shown in studies of chicken embryos. However, whether mammalian embryonic frontonasal ectomesenchyme contributes to the premaxillary bone has not been investigated and a tool to trace the contributions of the frontonasal ectomesenchyme to facial structures in mammals is lacking. The expression of the Alx3 gene is activated highly specifically in the frontonasal ectomesenchyme, but not in the maxillary mesenchyme, from the beginning of facial morphogenesis in mice. Here, we report the generation and characterization of a novel Alx3CreERT2 knock-in mouse line that express tamoxifen-inducible Cre DNA recombinase from the Alx3 locus. Tamoxifen treatment of Alx3CreERT2/+;Rosa26mTmG/+ embryos at E7.5, E8.5, E9.5, and E10.5, each induced specific labeling of the embryonic medial nasal and lateral nasal mesenchyme but not the maxillary mesenchyme. Lineage tracing of Alx3CreERT2-labeled frontonasal mesenchyme from E9.5 to E16.5 clearly showed that the frontonasal mesenchyme cells give rise to the osteoblasts generating the premaxillary bone. Furthermore, we characterize a Dlx1-Cre BAC transgenic mouse line that expresses Cre activity in the embryonic maxillary but not the frontonasal mesenchyme and show that the Dlx1-Cre labeled embryonic maxillary mesenchyme cells contribute to the maxillary bone as well as the soft tissues lateral to both the premaxillary and maxillary bones but not to the premaxillary bone. These results clearly demonstrate the developmental origin of the premaxillary bone from embryonic frontonasal ectomesenchyme cells in mice and confirm the evolutionary homology of the premaxilla across amniotes.

Anatomical Connectivity of the Intercalated Cells of the Amygdala

The intercalated cells of the amygdala (ITCs) are a fundamental processing structure in the amygdala that remain relatively understudied. They are phylogenetically conserved from insectivores through primates, inhibitory, and project to several of the main processing and output stations of the amygdala and basal forebrain. Through these connections, the ITCs are best known for their role in conditioned fear, where they are required for fear extinction learning and recall. Prior work on ITC connectivity is limited, and thus holistic characterization of their afferent and efferent connectivity in a genetically defined manner is incomplete. The ITCs express the FoxP2 transcription factor, affording genetic access to these neurons for viral input-output mapping. To fully characterize the anatomic connectivity of the ITCs, we used cre-dependent viral strategies in FoxP2-cre mice to reveal the projections of the main (mITC), caudal (cITC), and lateral (lITC) clusters along with their presynaptic sources of innervation. Broadly, the results confirm many known pathways, reveal previously unknown ones, and demonstrate important novel insights about each nucleus's unique connectivity profile and relative distributions. We show that the ITCs receive information from a wide range of cortical, subcortical, basal, amygdalar, hippocampal, and thalamic structures, and project broadly to areas of the basal forebrain, hypothalamus, and entire extent of the amygdala. The results provide a comprehensive map of their connectivity and suggest that the ITCs could potentially influence a broad range of behaviors by integrating information from a wide array of sources throughout the brain.

Phytotherapy of abnormality of fear memory: A narrative review of mechanisms

It is generally believed that in post-traumatic stress disorder (PTSD), the high expression of fear memory is mainly determined by amygdala hyperactivity and hippocampus hypoactivity. In this review, we firstly updated the mechanisms of fear memory, and then searched the experimental evidence of phytotherapy for fear memory in the past five years. Based on the summary of those experimental studies, we further discussed the future research strategies of plant medicines, including the study of the mechanism of specific brain regions, the optimal time for the prevention and treatment of fear memory-related diseases such as PTSD, and the development of new drugs with active components of plant medicines. Accordingly, plant medicines play a clear role in improving fear memory abnormalities and have the drug development potential in the treatment of fear-related disorders.

Transcriptomics reveals amygdala neuron regulation by fasting and ghrelin thereby promoting feeding

The central amygdala (CeA) consists of numerous genetically defined inhibitory neurons that control defensive and appetitive behaviors including feeding. Transcriptomic signatures of cell types and their links to function remain poorly understood. Using single-nucleus RNA sequencing, we describe nine CeA cell clusters, of which four are mostly associated with appetitive and two with aversive behaviors. To analyze the activation mechanism of appetitive CeA neurons, we characterized serotonin receptor 2a (Htr2a)-expressing neurons (CeA^Htr2a) that comprise three appetitive clusters and were previously shown to promote feeding. In vivo calcium imaging revealed that CeA^Htr2a neurons are activated by fasting, the hormone ghrelin, and the presence of food. Moreover, these neurons are required for the orexigenic effects of ghrelin. Appetitive CeA neurons responsive to fasting and ghrelin project to the parabrachial nucleus (PBN) causing inhibition of target PBN neurons. These results illustrate how the transcriptomic diversification of CeA neurons relates to fasting and hormone-regulated feeding behavior.

Molecular and cellular evolution of the amygdala across species analyzed by single-nucleus transcriptome profiling

The amygdala, or an amygdala-like structure, is found in the brains of all vertebrates and plays a critical role in survival and reproduction. However, the cellular architecture of the amygdala and how it has evolved remain elusive. Here, we generated single-nucleus RNA-sequencing data for more than 200,000 cells in the amygdala of humans, macaques, mice, and chickens. Abundant neuronal cell types from different amygdala subnuclei were identified in all datasets. Cross-species analysis revealed that inhibitory neurons and inhibitory neuron-enriched subnuclei of the amygdala were well-conserved in cellular composition and marker gene expression, whereas excitatory neuron-enriched subnuclei were relatively divergent. Furthermore, LAMP5⁺ interneurons were much more abundant in primates, while DRD2⁺ inhibitory neurons and LAMP5⁺SATB2⁺ excitatory neurons were dominant in the human central amygdalar nucleus (CEA) and basolateral amygdalar complex (BLA), respectively. We also identified CEA-like neurons and their species-specific distribution patterns in chickens. This study highlights the extreme cell-type diversity in the amygdala and reveals the conservation and divergence of cell types and gene expression patterns across species that may contribute to species-specific adaptations.

Effects of footshock stress on social behavior and neuronal activation in the medial prefrontal cortex and amygdala of male and female mice

Social behavior is complex and fundamental, and its deficits are common pathological features for several psychiatric disorders including anxiety, depression, and posttraumatic stress disorder. Acute stress may have a negative impact on social behavior, and these effects can vary based on sex. The aim of this study was to explore the effect of acute footshock stress, using analogous parameters to those commonly used in fear conditioning assays, on the sociability of male and female C57BL/6J mice in a standard social approach test. Animals were divided into two main groups of footshock stress (22 male, 24 female) and context exposed control (23 male and 22 female). Each group had mice that were treated intraperitoneally with either the benzodiazepine-alprazolam (control: 10 male, 10 female; stress: 11 male, 11 female), or vehicle (control: 13 male, 12 female; stress: 11 male, 13 female). In all groups, neuronal activation during social approach was assessed using immunohistochemistry against the immediate early gene product cFos. Although footshock stress did not significantly alter sociability or latency to approach a social stimulus, it did increase defensive tail-rattling behavior specifically in males (p = 0.0022). This stress-induced increase in tail-rattling was alleviated by alprazolam (p = 0.03), yet alprazolam had no effect on female tail-rattling behavior in the stress group. Alprazolam lowered cFos expression in the medial prefrontal cortex (p = 0.001 infralimbic area, p = 0.02 prelimbic area), and social approach induced sex-dependent differences in cFos activation in the ventromedial intercalated cell clusters (p = 0.04). Social approach following stress-induced cFos expression was positively correlated with latency to approach and negatively correlated with sociability in the prelimbic area and multiple amygdala subregions (all p < 0.05). Collectively, our results suggest that acute footshock stress induces sex-dependent alterations in defensiveness and differential patterns of cFos activation during social approach.

Molecular Diversity of Neuron Types in the Salamander Amygdala and Implications for Amygdalar Evolution

The amygdala is a complex brain structure in the vertebrate telencephalon, essential for regulating social behaviors, emotions, and (social) cognition. In contrast to the vast majority of neuron types described in the many nuclei of the mammalian amygdala, little is known about the neuronal diversity in non-mammals, making reconstruction of its evolution particularly difficult. Here, we characterize glutamatergic neuron types in the amygdala of the urodele amphibian Pleurodeles waltl. Our single-cell RNA sequencing data indicate the existence of at least ten distinct types and subtypes of glutamatergic neurons in the salamander amygdala. These neuron types are molecularly distinct from neurons in the ventral pallium (VP), suggesting that the pallial amygdala and the VP are two separate areas in the telencephalon. In situ hybridization for marker genes indicates that amygdalar glutamatergic neuron types are located in three major subdivisions: the lateral amygdala, the medial amygdala, and a newly defined area demarcated by high expression of the transcription factor Sim1. The gene expression profiles of these neuron types suggest similarities with specific neurons in the sauropsid and mammalian amygdala. In particular, we identify Sim1+ and Sim1+ Otp+ expressing neuron types, potentially homologous to the mammalian nucleus of the lateral olfactory tract (NLOT) and to hypothalamic-derived neurons of the medial amygdala, respectively. Taken together, our results reveal a surprising diversity of glutamatergic neuron types in the amygdala of salamanders, despite the anatomical simplicity of their brain. These results offer new insights on the cellular and anatomical complexity of the amygdala in tetrapod ancestors.

Amygdala Intercalated Cells: Gate Keepers and Conveyors of Internal State to the Circuits of Emotion

Generating adaptive behavioral responses to emotionally salient stimuli requires evaluation of complex associations between multiple sensations, the surrounding context, and current internal state. Neural circuits within the amygdala parse this emotional information, undergo synaptic plasticity to reflect learned associations, and evoke appropriate responses through their projections to the brain regions orchestrating these behaviors. Information flow within the amygdala is regulated by the intercalated cells (ITCs), which are densely packed clusters of GABAergic neurons that encircle the basolateral amygdala (BLA) and provide contextually relevant feedforward inhibition of amygdala nuclei, including the central and BLA. Emerging studies have begun to delineate the unique contribution of each ITC cluster and establish ITCs as key loci of plasticity in emotional learning. In this review, we summarize the known connectivity and function of individual ITC clusters and explore how different neuromodulators conveying internal state act via ITC gates to shape emotionally motivated behavior. We propose that the behavioral state-dependent function of ITCs, their unique genetic profile, and rich expression of neuromodulator receptors make them potential therapeutic targets for disorders, such as anxiety, schizophrenia spectrum, and addiction.

Cell-type specific changes in PKC-delta neurons of the central amygdala during alcohol withdrawal

The central amygdala (CeA) contains a diverse population of cells, including multiple subtypes of GABAergic neurons, along with glia and epithelial cells. Specific CeA cell types have been shown to affect alcohol consumption in animal models of dependence and may be involved in negative affect during alcohol withdrawal. We used single-nuclei RNA sequencing to determine cell-type specificity of differential gene expression in the CeA induced by alcohol withdrawal. Cells within the CeA were classified using unbiased clustering analyses and identified based on the expression of known marker genes. Differential gene expression analysis was performed on each identified CeA cell-type. It revealed differential gene expression in astrocytes and GABAergic neurons associated with alcohol withdrawal. GABAergic neurons were further subclassified into 13 clusters of cells. Analyzing transcriptomic responses in these subclusters revealed that alcohol exposure induced multiple differentially expressed genes in one subtype of CeA GABAergic neurons, the protein kinase C delta (PKCδ) expressing neurons. These results suggest that PKCδ neurons in the CeA may be uniquely sensitive to the effects of alcohol exposure and identify a novel population of cells in CeA associated with alcohol withdrawal.

Functional connectivity of intercalated nucleus with medial amygdala: A circuit relevant for chemosignal processing

Medial amygdala processes social/reproductive chemosensory input, and its projections to preoptic and hypothalamic areas evoke appropriate behavioral and physiological responses. We and others have shown that different chemosensory signals elicit differential responses in medial amygdala subregions and in adjacent main intercalated nucleus (mICN). The largely GABAergic mICN receives no direct chemosensory input but, as we show, mICN has functional circuit connections with medial amygdala that could be responsible both for mICN chemosensitivity and for a feedforward inhibitory effect on posterior medial amygdala; which, in turn would affect chemosignal response. mICN is subject to inhibition by dopamine and is probably regulated by neuropeptides and input from frontal cortex. Thus, mICN is in position to modify chemosensory processing in medial amygdala and behavioral responses to social signals, according to internal brain state. Patch-clamp recordings from neurons in each relevant nucleus in horizontal brain-slices, with electrical stimulation in adjacent nuclei, reveal multiple functional connections between medial amygdala subregions and mICN. We highlight a triangular circuit which may underlie mICN chemosensitivity and its potential for modifying chemosensory information transmitted to basal forebrain. Anterior medial amygdala, which receives most of the chemosensory input, connects to posterior medial amygdala directly and both areas send information on to basal forebrain. Anterior medial amygdala can also modulate posterior medial amygdala indirectly via the mICN side-loop, which also provides a pathway for modulation by cortical input or, when inhibited by dopamine, could allow a more automatic response - as proposed for other amygdala circuits with similar ICN side loops.

The development and evolution of inhibitory neurons in primate cerebrum

Neuroanatomists have long speculated that expanded primate brains contain an increased morphological diversity of inhibitory neurons (INs)1, and recent studies have identified primate-specific neuronal populations at the molecular level2. However, we know little about the developmental mechanisms that specify evolutionarily novel cell types in the brain. Here, we reconstruct gene expression trajectories specifying INs generated throughout the neurogenic period in macaques and mice by analysing the transcriptomes of 250,181 cells. We find that the initial classes of INs generated prenatally are largely conserved among mammals. Nonetheless, we identify two contrasting developmental mechanisms for specifying evolutionarily novel cell types during prenatal development. First, we show that recently identified primate-specific TAC3 striatal INs are specified by a unique transcriptional programme in progenitors followed by induction of a distinct suite of neuropeptides and neurotransmitter receptors in new-born neurons. Second, we find that multiple classes of transcriptionally conserved olfactory bulb (OB)-bound precursors are redirected to expanded primate white matter and striatum. These classes include a novel peristriatal class of striatum laureatum neurons that resemble dopaminergic periglomerular cells of the OB. We propose an evolutionary model in which conserved initial classes of neurons supplying the smaller primate OB are reused in the enlarged striatum and cortex. Together, our results provide a unified developmental taxonomy of initial classes of mammalian INs and reveal multiple developmental mechanisms for neural cell type evolution.

Neurobehavioral abnormalities following prenatal psychosocial stress are differentially modulated by maternal environment

Prenatal stress (PS) is associated with increased vulnerability to affective disorders. Transplacental glucocorticoid passage and stress-induced maternal environment alterations are recognized as potential routes of transmission that can fundamentally alter neurodevelopment. However, molecular mechanisms underlying aberrant emotional outcomes or the individual contributions intrauterine stress versus maternal environment play in shaping these mechanisms remain unknown. Here, we report anxiogenic behaviors, anhedonia, and female hypothalamic-pituitary-adrenal axis hyperactivity as a consequence of psychosocial PS in mice. Evidence of fetal amygdala programming precedes these abnormalities. In adult offspring, we observe amygdalar transcriptional changes demonstrating sex-specific dysfunction in synaptic transmission and neurotransmitter systems. We find these abnormalities are primarily driven by in-utero stress exposure. Importantly, maternal care changes postnatally reverse anxiety-related behaviors and partially rescue gene alterations associated with neurotransmission. Our data demonstrate the influence maternal environment exerts in shaping offspring emotional development despite deleterious effects of intrauterine stress.

Novel Perspectives on the Development of the Amygdala in Rodents

The amygdala is a hyperspecialized brain region composed of strongly inter- and intraconnected nuclei involved in emotional learning and behavior. The cellular heterogeneity of the amygdalar nuclei has complicated straightforward conclusions on their developmental origin, and even resulted in contradictory data. Recently, the concentric ring theory of the pallium and the radial histogenetic model of the pallial amygdala have cleared up several uncertainties that plagued previous models of amygdalar development. Here, we provide an extensive overview on the developmental origin of the nuclei of the amygdaloid complex. Starting from older gene expression data, transplantation and lineage tracing studies, we systematically summarize and reinterpret previous findings in light of the novel perspectives on amygdalar development. In addition, migratory routes that these cells take on their way to the amygdala are explored, and known transcription factors and guidance cues that seemingly drive these cells toward the amygdala are emphasized. We propose some future directions for research on amygdalar development and highlight that a better understanding of its development could prove critical for the treatment of several neurodevelopmental and neuropsychiatric disorders.

Neural Circuits for Social Interactions: From Microcircuits to Input-Output Circuits

Social behaviors entail responses to social information and requires the perception and integration of social cues through a complex cognition process that involves attention, memory, motivation, and emotion. Neurobiological and molecular mechanisms underlying social behavior are highly conserved across species, and inter- and intra-specific variability observed in social behavior can be explained to large extent by differential activity of a conserved neural network. However, neural microcircuits and precise networks involved in social behavior remain mysterious. In this review, we summarize the microcircuits and input-output circuits on the molecular, cellular, and network levels of different social interactions, such as social exploration, social hierarchy, social memory, and social preference. This review provides a broad view of how multiple microcircuits and input-output circuits converge on the medial prefrontal cortex, hippocampus, and amygdala to regulate complex social behaviors, as well as a potential novel view for better control over pathological development.

Sex-Specific Social Behavior and Amygdala Proteomic Deficits in Foxp2 +/- Mutant Mice

In humans, mutations in the transcription factor encoding gene, FOXP2, are associated with language and Autism Spectrum Disorders (ASD), the latter characterized by deficits in social interactions. However, little is known regarding the function of Foxp2 in male or female social behavior. Our previous studies in mice revealed high expression of Foxp2 within the medial subnucleus of the amygdala (MeA), a limbic brain region highly implicated in innate social behaviors such as mating, aggression, and parental care. Here, using a comprehensive panel of behavioral tests in male and female Foxp2 +/- heterozygous mice, we investigated the role Foxp2 plays in MeA-linked innate social behaviors. We reveal significant deficits in olfactory processing, social interaction, mating, aggressive, and parental behaviors. Interestingly, some of these deficits are displayed in a sex-specific manner. To examine the consequences of Foxp2 loss of function specifically in the MeA, we conducted a proteomic analysis of microdissected MeA tissue. This analyses revealed putative sex differences expression of a host of proteins implicated in neuronal communication, connectivity, and dopamine signaling. Consistent with this, we discovered that MeA Foxp2-lineage cells were responsive to dopamine with differences between males and females. Thus, our findings reveal a central and sex-specific role for Foxp2 in social behavior and MeA function.

Midbrain dopaminergic inputs gate amygdala intercalated cell clusters by distinct and cooperative mechanisms in male mice

Dopaminergic signaling plays an important role in associative learning, including fear and extinction learning. Dopaminergic midbrain neurons encode prediction error-like signals when threats differ from expectations. Within the amygdala, GABAergic intercalated cell (ITC) clusters receive one of the densest dopaminergic projections, but their physiological consequences are incompletely understood. ITCs are important for fear extinction, a function thought to be supported by activation of ventromedial ITCs that inhibit central amygdala fear output. In mice, we reveal two distinct novel mechanisms by which mesencephalic dopaminergic afferents control ITCs. Firstly, they co-release GABA to mediate rapid, direct inhibition. Secondly, dopamine suppresses inhibitory interactions between distinct ITC clusters via presynaptic D1 receptors. Early extinction training augments both GABA co-release onto dorsomedial ITCs and dopamine-mediated suppression of dorso- to ventromedial inhibition between ITC clusters. These findings provide novel insights into dopaminergic mechanisms shaping the activity balance between distinct ITC clusters that could support their opposing roles in fear behavior.

Apical intercalated cell cluster: A distinct sensory regulator in the amygdala

GABAergic neurons regulate different aspects of information processing in the amygdala. Among these are clusters of intercalated cells (ITCs), which have been implicated in fear-related behaviors. Although a few of the ITC clusters have been studied, the functional role of apical ITCs (apITCs) is unknown. Here, we combine monosynaptic rabies tracing with optogenetics and demonstrate that apITCs receive synaptic input from medial geniculate nucleus (MGm), posterior intralaminar nucleus (PIN), and medial dorsal nucleus of the thalamus and from a diverse range of cortical areas including temporal association, entorhinal, insular, piriform, and somatosensory cortex. Upon fear learning, PIN/MGm inputs are strengthened, indicative of their involvement in fear behaviors. 3-D reconstruction of apITCs reveals local arborization and innervation of the dorsal striatum and lateral amygdala. We further show that apITCs provide sensory feedforward inhibition to LA principal cells, a putative mechanism for controlling plasticity during fear learning.

A role for sustained MAPK activity in the mouse ventral telencephalon

The MAPK pathway is a major growth signal that has been implicated during the development of progenitors, neurons, and glia in the embryonic brain. Here, we show that the MAPK pathway plays an important role in the generation of distinct cell types from progenitors in the ventral telencephalon. Our data reveal that phospho-p44/42 (called p-ERK1/2) and the ETS transcription factor Etv5, both downstream effectors in the MAPK pathway, show a regional bias in expression during ventral telencephalic development, with enriched expression in the dorsal region of the LGE and ventral region of the MGE at E13.5 and E15.5. Interestingly, expression of both factors becomes more uniform in ventricular zone (VZ) progenitors by E18.5. To gain insight into the role of MAPK activity during progenitor cell development, we used a cre inducible constitutively active MEK1 allele (Rosa^MEK1DD/+) in combination with a ventral telencephalon enriched cre (Gsx2e-cre) or a dorsal telencephalon enriched cre (Emx1^cre/+). Sustained MEK/MAPK activity in the ventral telencephalon (Gsx2e-cre; Rosa^MEK1DD/+) expanded dorsal lateral ganglionic eminence (dLGE) enriched genes (Gsx2 and Sp8) and oligodendrocyte progenitor cell (OPC) markers (Olig2, Pdgfrα, and Sox10), and also reduced markers in the ventral (v) LGE domain (Isl1 and Foxp1). Activation of MEK/MAPK activity in the dorsal telencephalon (Emx1^cre/+; Rosa^MEK1DD/+) did not initially activate the expression of dLGE or OPC genes at E15.5 but ectopic expression of Gsx2 and OPC markers were observed at E18.5. These results support the idea that MAPK activity as readout by p-ERK1/2 and Etv5 expression is enriched in distinct subdomains of ventral telencephalic progenitors during development. In addition, sustained activation of the MEK/MAPK pathway in the ventral or dorsal telencephalon influences dLGE and OPC identity from progenitors.

The potassium channel Kv4.2 regulates dendritic spine morphology, electroencephalographic characteristics and seizure susceptibility in mice

The voltage-gated potassium channel Kv4.2 is a critical regulator of dendritic excitability in the hippocampus and is crucial for dendritic signal integration. Kv4.2 mRNA and protein expression as well as function are reduced in several genetic and pharmacologically induced rodent models of epilepsy and autism. It is not known, however, whether reduced Kv4.2 is just an epiphenomenon or a disease-contributing cause of neuronal hyperexcitability and behavioral impairments in these neurological disorders. To address this question, we used male and female mice heterozygous for a Kv.2 deletion and adult-onset manipulation of hippocampal Kv4.2 expression in male mice to assess the role of Kv4.2 in regulating neuronal network excitability, morphology and anxiety-related behaviors. We observed a reduction in dendritic spine density and reduced proportions of thin and stubby spines but no changes in anxiety, overall activity, or retention of conditioned freezing memory in Kv4.2 heterozygous mice compared with wildtype littermates. Using EEG analyses, we showed elevated theta power and increased spike frequency in Kv4.2 heterozygous mice under basal conditions. In addition, the latency to onset of kainic acid-induced seizures was significantly shortened in Kv4.2 heterozygous mice compared with wildtype littermates, which was accompanied by a significant increase in theta power. By contrast, overexpressing Kv4.2 in wildtype mice through intrahippocampal injection of Kv4.2-expressing lentivirus delayed seizure onset and reduced EEG power. These results suggest that Kv4.2 is an important regulator of neuronal network excitability and dendritic spine morphology, but not anxiety-related behaviors. In the future, manipulation of Kv4.2 expression could be used to alter seizure susceptibility in epilepsy.

Temporally Distinct Roles for the Zinc Finger Transcription Factor Sp8 in the Generation and Migration of Dorsal Lateral Ganglionic Eminence (dLGE)-Derived Neuronal Subtypes in the Mouse

Progenitors in the dorsal lateral ganglionic eminence (dLGE) are known to give rise to olfactory bulb (OB) interneurons and intercalated cells (ITCs) of the amygdala. The dLGE enriched transcription factor Sp8 is required for the normal generation of ITCs as well as OB interneurons, particularly the calretinin (CR)-expressing subtype. In this study, we used a genetic gain-of-function approach in mice to examine the roles Sp8 plays in controlling the development of dLGE-derived neuronal subtypes. Misexpression of Sp8 throughout the ventral telencephalic subventricular zone (SVZ) from early embryonic stages, led to an increased generation of ITCs which was dependent on Tshz1 gene dosage. Additionally, Sp8 misexpression impaired rostral migration of OB interneurons with clusters of CR interneurons seen in the SVZ along with decreased differentiation of calbindin OB interneurons. Sp8 misexpression throughout the ventral telencephalon also reduced ventral LGE neuronal subtypes including striatal projection neurons. Delaying Sp8 misexpression until E14-15 rescued the striatal and amygdala phenotypes but only partially rescued OB interneuron reductions, consistent with an early window of striatal and amygdala neurogenesis and ongoing OB interneuron generation at this late stage. Our results demonstrate critical roles for the timing and neuronal cell-type specificity of Sp8 expression in mouse LGE neurogenesis.

Prokineticin signaling in heart-brain developmental axis: Therapeutic options for heart and brain injuries

Heart and brain development occur simultaneously during the embryogenesis, and both organ development and injuries are interconnected. Early neuronal and cardiac injuries share mutual cellular events, such as angiogenesis and plasticity that could either delay disease progression or, in the long run, result in detrimental health effects. For this reason, the common mechanisms provide a new and previously undervalued window of opportunity for intervention. Because angiogenesis, cardiogenesis and neurogenesis are essential for the development and regeneration of the heart and brain, we discuss therein the role of prokineticin as an angiogenic neuropeptide in heart-brain development and injuries. We focus on the role of prokineticin signaling and the effect of drugs targeting prokineticin receptors in neuroprotection and cardioprotection, with a special emphasis on heart failure, neurodegenerativParkinson's disease and ischemic heart and brain injuries. Indeed, prokineticin triggers common pro-survival signaling pathway in heart and brain. Our review aims at stimulating researchers and clinicians in neurocardiology to focus on the role of prokineticin signaling in the reciprocal interaction between heart and brain. We hope to facilitate the discovery of new treatment strategies, acting in both heart and brain degenerative diseases.

A Genetically Defined Compartmentalized Striatal Direct Pathway for Negative Reinforcement

The striosome compartment within the dorsal striatum has been implicated in reinforcement learning and regulation of motivation, but how striosomal neurons contribute to these functions remains elusive. Here, we show that a genetically identified striosomal population, which expresses the Teashirt family zinc finger 1 (Tshz1) and belongs to the direct pathway, drives negative reinforcement and is essential for aversive learning in mice. Contrasting a "conventional" striosomal direct pathway, the Tshz1 neurons cause aversion, movement suppression, and negative reinforcement once activated, and they receive a distinct set of synaptic inputs. These neurons are predominantly excited by punishment rather than reward and represent the anticipation of punishment or the motivation for avoidance. Furthermore, inhibiting these neurons impairs punishment-based learning without affecting reward learning or movement. These results establish a major role of striosomal neurons in behaviors reinforced by punishment and moreover uncover functions of the direct pathway unaccounted for in classic models.

FOXP transcription factors in vertebrate brain development, function, and disorders

FOXP transcription factors are an evolutionarily ancient protein subfamily coordinating the development of several organ systems in the vertebrate body. Association of their genes with neurodevelopmental disorders has sparked particular interest in their expression patterns and functions in the brain. Here, FOXP1, FOXP2, and FOXP4 are expressed in distinct cell type-specific spatiotemporal patterns in multiple regions, including the cortex, hippocampus, amygdala, basal ganglia, thalamus, and cerebellum. These varied sites and timepoints of expression have complicated efforts to link FOXP1 and FOXP2 mutations to their respective developmental disorders, the former affecting global neural functions and the latter specifically affecting speech and language. However, the use of animal models, particularly those with brain region- and cell type-specific manipulations, has greatly advanced our understanding of how FOXP expression patterns could underlie disorder-related phenotypes. While many questions remain regarding FOXP expression and function in the brain, studies to date have illuminated the roles of these transcription factors in vertebrate brain development and have greatly informed our understanding of human development and disorders. This article is categorized under: Nervous System Development > Vertebrates: General Principles Gene Expression and Transcriptional Hierarchies > Gene Networks and Genomics Nervous System Development > Vertebrates: Regional Development.

Genetic pathways involved in human speech disorders

Rare genetic variants that disrupt speech development provide entry points for deciphering the neurobiological foundations of key human capacities. The value of this approach is illustrated by FOXP2, a transcription factor gene that was implicated in speech apraxia, and subsequently investigated using human cell-based systems and animal models. Advances in next-generation sequencing, coupled to de novo paradigms, facilitated discovery of etiological variants in additional genes in speech disorder cohorts. As for other neurodevelopmental syndromes, gene-driven studies show blurring of boundaries between diagnostic categories, with some risk genes shared across speech disorders, intellectual disability and autism. Convergent evidence hints at involvement of regulatory genes co-expressed in early human brain development, suggesting that etiological pathways could be amenable for investigation in emerging neural models such as cerebral organoids.

Physical interactions between Gsx2 and Ascl1 balance progenitor expansion versus neurogenesis in the mouse lateral ganglionic eminence

The Gsx2 homeodomain transcription factor promotes neural progenitor identity in the lateral ganglionic eminence (LGE), despite upregulating the neurogenic factor Ascl1. How this balance in maturation is maintained is unclear. Here, we show that Gsx2 and Ascl1 are co-expressed in subapical progenitors that have unique transcriptional signatures in LGE ventricular zone (VZ) cells. Moreover, whereas Ascl1 misexpression promotes neurogenesis in dorsal telencephalic progenitors, the co-expression of Gsx2 with Ascl1 inhibits neurogenesis. Using luciferase assays, we found that Gsx2 reduces the ability of Ascl1 to activate gene expression in a dose-dependent and DNA binding-independent manner. Furthermore, Gsx2 physically interacts with the basic helix-loop-helix (bHLH) domain of Ascl1, and DNA-binding assays demonstrated that this interaction interferes with the ability of Ascl1 to bind DNA. Finally, we modified a proximity ligation assay for tissue sections and found that Ascl1-Gsx2 interactions are enriched within LGE VZ progenitors, whereas Ascl1-Tcf3 (E-protein) interactions predominate in the subventricular zone. Thus, Gsx2 contributes to the balance between progenitor maintenance and neurogenesis by physically interacting with Ascl1, interfering with its DNA binding and limiting neurogenesis within LGE progenitors.

Chronic psychosocial stress during pregnancy affects maternal behavior and neuroendocrine function and modulates hypothalamic CRH and nuclear steroid receptor expression

Postpartum depression (PPD) affects up to 20% of mothers and has negative consequences for both mother and child. Although exposure to psychosocial stress during pregnancy and abnormalities in the hypothalamic pituitary adrenal (HPA) axis have been linked to PPD, molecular changes in the brain that contribute to this disease remain unknown. This study utilized a novel chronic psychosocial stress paradigm during pregnancy (CGS) to investigate the effects of psychosocial stress on maternal behavior, neuroendocrine function, and gene expression changes in molecular regulators of the HPA axis in the early postpartum period. Postpartum female mice exposed to CGS display abnormalities in maternal behavior, including fragmented and erratic maternal care patterns, and the emergence of depression and anxiety-like phenotypes. Dysregulation in postpartum HPA axis function, evidenced by blunted circadian peak and elevation of stress-induced corticosterone levels, was accompanied by increased CRH mRNA expression and a reduction in CRH receptor 1 in the paraventricular nucleus of the hypothalamus (PVN). We further observed decreased PVN expression of nuclear steroid hormone receptors associated with CRH transcription, suggesting these molecular changes could underlie abnormalities in postpartum HPA axis and behavior observed. Overall, our study demonstrates that psychosocial stress during pregnancy induces changes in neuroendocrine function and maternal behavior in the early postpartum period and introduces our CGS paradigm as a viable model that can be used to further dissect the molecular defects that lead to PPD.

Dlx1/2 are Central and Essential Components in the Transcriptional Code for Generating Olfactory Bulb Interneurons

Generation of olfactory bulb (OB) interneurons requires neural stem/progenitor cell specification, proliferation, differentiation, and young interneuron migration and maturation. Here, we show that the homeobox transcription factors Dlx1/2 are central and essential components in the transcriptional code for generating OB interneurons. In Dlx1/2 constitutive null mutants, the differentiation of GSX2+ and ASCL1+ neural stem/progenitor cells in the dorsal lateral ganglionic eminence is blocked, resulting in a failure of OB interneuron generation. In Dlx1/2 conditional mutants (hGFAP-Cre; Dlx1/2F/- mice), GSX2+ and ASCL1+ neural stem/progenitor cells in the postnatal subventricular zone also fail to differentiate into OB interneurons. In contrast, overexpression of Dlx1&2 in embryonic mouse cortex led to ectopic production of OB-like interneurons that expressed Gad1, Sp8, Sp9, Arx, Pbx3, Etv1, Tshz1, and Prokr2. Pax6 mutants generate cortical ectopia with OB-like interneurons, but do not do so in compound Pax6; Dlx1/2 mutants. We propose that DLX1/2 promote OB interneuron development mainly through activating the expression of Sp8/9, which further promote Tshz1 and Prokr2 expression. Based on this study, in combination with earlier ones, we propose a transcriptional network for the process of OB interneuron development.

Teashirt 1 (Tshz1) is essential for the development, survival and function of hypoglossal and phrenic motor neurons in mouse

Feeding and breathing are essential motor functions and rely on the activity of hypoglossal and phrenic motor neurons that innervate the tongue and diaphragm, respectively. Little is known about the genetic programs that control the development of these neuronal subtypes. The transcription factor Tshz1 is strongly and persistently expressed in developing hypoglossal and phrenic motor neurons. We used conditional mutation of Tshz1 in the progenitor zone of motor neurons (Tshz1^{MN Δ}) to show that Tshz1 is essential for survival and function of hypoglossal and phrenic motor neurons. Hypoglossal and phrenic motor neurons are born in correct numbers, but many die between embryonic day 13.5 and 14.5 in Tshz1^{MN Δ} mutant mice. In addition, innervation and electrophysiological properties of phrenic and hypoglossal motor neurons are altered. Severe feeding and breathing problems accompany this developmental deficit. Although motor neuron survival can be rescued by elimination of the pro-apoptotic factor Bax, innervation, feeding and breathing defects persist in Bax^-/-; Tshz1^{MN Δ} mutants. We conclude that Tshz1 is an essential transcription factor for the development and physiological function of phrenic and hypoglossal motor neurons.

Tinbergen's challenge for the neuroscience of behavior

Nobel laureate Nikolaas Tinbergen provided clear criteria for declaring a neuroscience problem solved, criteria which despite the passage of more than 50 years and vastly expanded neuroscience tool kits remain applicable today. Tinbergen said for neuroscientists to claim that a behavior is understood, they must correspondingly understand its (i) development and its (ii) mechanisms and its (iii) function and its (iv) evolution. Now, all four of these domains represent hotbeds of current experimental work, each using arrays of new techniques which overlap only partly. Thus, as new methodologies come online, from single-nerve-cell RNA sequencing, for example, to smart FISH, large-scale calcium imaging from cortex and deep brain structures, computational ethology, and so on, one person, however smart, cannot master everything. Our response to the likely “fracturing” of neuroscience recognizes the value of ever larger consortia. This response suggests new kinds of problems for (i) funding and (ii) the fair distribution of credit, especially for younger scientists.

Valence coding in amygdala circuits

The neural mechanisms underlying emotional valence are at the interface between perception and action, integrating inputs from the external environment with past experiences to guide the behavior of an organism. Depending on the positive or negative valence assigned to an environmental stimulus, the organism will approach or avoid the source of the stimulus. Multiple convergent studies have demonstrated that the amygdala complex is a critical node of the circuits assigning valence. Here we examine the current progress in identifying valence coding properties of neural populations in different nuclei of the amygdala, based on their activity, connectivity, and gene expression profile.