Linking emotional valence and anxiety in a mouse insula-amygdala circuit

Machine Learning-Enabled Emotion Recognition by Multisource Throat Signals

Emotion monitoring plays a crucial role in mental health management. However, traditional methods of emotion recognition predominantly rely on subjective questionnaires or facial expression analyses, which are often inadequate for continuous and highly accurate monitoring. In this study, we propose a high-precision, fine-grained emotion recognition system based on multisource throat physiological signals. The system collects signals through optimized flexible multiporous skin sensors and analyzes them using machine learning models capable of efficiently capturing complex feature interactions. First, we adopt a two-step cross-linking strategy to modulate the porous structure of the sensitive layer to enable accurate detection of the diverse and weak physiological signals in the throat. By extracting four-dimensional features from the input of 7025 samples, the platform based on the Light Gradient Boosting Machine (LightGBM) efficiently captures their nonlinear interactions, ultimately achieving precise classification of five emotional states (relaxation, surprise, disgust, fear, and neutral) with an accuracy of 98.9%. Further validation on an independent data set reveals an average emotion recognition accuracy of 99.3%, demonstrating the system's robustness and reliability in real-world applications. This work provides a viable technological solution for real-time and continuous emotion monitoring, offering significant potential in mental health management and related fields.

The neurobiology of ticklishness

Ticklishness is an idiosyncratic form of touch observed in multiple animal species, including humans. Although commonly regarded as trivial, it involves complex neurobiological mechanisms and diverse behavioral phenomena observed across species. Two distinct forms exist: knismesis, a mild tingling sensation elicited by gentle touch, and gargalesis, an intense sensation associated with involuntary laughter. Advocating the importance of clearly distinguishing these two types of ticklishness, this review synthesizes current knowledge on their neuronal underpinnings. Topics include somatosensory processing, self-tickling and sensory attenuation, emotional modulation, sociosexual dimensions, and evolutionary perspectives, among others. Special attention is given to the ambivalent nature of gargalesis, challenging conventional single-dimensional models of emotional valence. Ultimately, studying ticklishness provides a valuable opportunity to investigate playful emotional experiences from a naturalistic perspective, addressing fundamental yet underrepresented questions in contemporary neuroscience. Far from trivial, ticklishness thus provides valuable insights into the neural mechanisms underlying complex, context-dependent emotional and social experiences.

Neural mechanisms, influencing factors and interventions in empathic pain

Empathic pain, defined as the emotional resonance with the suffering of others, is akin to the observer's own experience of pain and is vital for building and sustaining positive interpersonal relationships. Despite its importance, the neural mechanism of empathic pain remains poorly understood. In this review, we integrated and summarized the currently knowledge on the neural networks associated with empathic pain, focusing on key brain regions such as the insula, anterior cingulate cortex (ACC), ventral tegmental area (VTA), nucleus accumbens (NAc), and locus coeruleus (LC)/norepinephrine (NE)-sympatho-adrenomedullar (LC/NE-SAM) system. We also reviewed the factors that affect empathic pain, including gender, personal beliefs, the intimacy of relationships, and the nature of interpersonal relationships, and highlighted the central role of the insula and ACC in the neural circuitry of empathy, the importance of the IC-BLA and ACC-NAc/VTA connections in modulating empathic pain, and the involvement of the LC/NE-SAM system in mediating pain empathy. We further discussed how gender significantly influences empathic pain, with women showing more intense emotional reactions to social distress than men. It also summarized the roles of personal pain history and empathy levels in modulating empathic responses. Furthermore, the review emphasized the impact of social factors such as the nature of interpersonal relationships and experiences of social exclusion on empathic pain. By providing a detailed exploration of the neural mechanisms and influencing factors of empathic pain, this review aims to establish a robust foundation for developing targeted therapeutic strategies and improving pain management in clinical settings.

Opposite-sex pairing alters social-induced GCaMP and dopamine activity in the insula of male prairie voles

The prairie vole (Microtus ochrogaster) is a monogamous rodent species which displays selective social behaviors to conspecifics after establishing a pair-bonded relationship, specifically partner-directed affiliation and stranger-directed aggression. This social selectivity relies on the ability of an individual to respond appropriately to a social context and requires salience detection and valence assignment. The anterior insular cortex (aIC) has been implicated in stimulus processing and categorization across a variety of contexts, but its regulation of pair bond-induced social selectivity in prairie voles has not been studied. Here, we examined whether neural activity and gene expression in the aIC change during male-female pairings in male prairie voles. Opposite-sex pairing was characterized by changes to calcium and dopamine transients in the aIC that corresponded with the display of social selectivity across pair bond maturation. Furthermore, D1 and D2 receptor mRNA expression was significantly higher in males after 48 h of cohabitation with a female partner compared to same-sex housed males, and D2 mRNA remained elevated after a week of cohabitation. Together, these results implicate a role for dopamine and its receptors in the aIC across the transition from early- to late-phase pair bonding.

Neural circuit underlying individual differences in visual escape habituation

Emotions like fear help organisms respond to threats. Repeated predator exposure leads to adaptive responses with unclear neural mechanisms behind individual variability. We identify two escape behaviors in mice-persistent escape (T1) and rapid habituation (T2)-linked to unique arousal states under repetitive looming stimuli. Combining multichannel recording, circuit mapping, optogenetics, and behavioral analyses, we find parallel pathways from the superior colliculus (SC) to the basolateral amygdala (BLA) via the ventral tegmental area (VTA) for T1 and via the mediodorsal thalamus (MD) for T2. T1 involves heightened arousal, while T2 features rapid habituation. The MD integrates SC and insular cortex inputs to modulate arousal and defensive behaviors. This work reveals neural circuits underpinning adaptive threat responses and individual variability.

Multidimensional mechanisms of anxiety and depression in Parkinson's disease: Integrating neuroimaging, neurocircuits, and molecular pathways

Anxiety and depression are common non-motor symptoms of Parkinson's disease (PD) that significantly affect patients' quality of life. In recent years, our understanding of PD has advanced through multifaceted studies on the pathological mechanisms associated with anxiety and depression in PD. These classic psychiatric symptoms involve complex pathophysiology, with both distinct features and connections to the mechanisms underlying the aetiology of PD. Furthermore, the co-occurrence of anxiety and depression in PD blurs the boundaries between them. Therefore, a comprehensive summary of the pathogenic mechanisms associated with anxiety and depression will aid in better addressing the emergence of these classic psychiatric symptoms in PD. This article integrates neuroanatomical, neural projection, neurotransmitter, neuroinflammatory, brain-gut axis, neurotrophic, hypothalamic-pituitary-adrenal axis, and genetic perspectives to provide a comprehensive description of the core pathological alterations underlying anxiety and depression in PD, aiming to provide an up-to-date perspective and broader therapeutic prospects for PD patients suffering from anxiety or depression.

Sex-dependent effects of stress on aIC-NAc circuit neuroplasticity: Role of the endocannabinoid system

Stress is a major risk factor for psychiatric disorders and affects neuroplasticity in brain areas like the nucleus accumbens core (NAcC) and the insular cortex (IC). This study examined neuroplasticity changes in the aIC-NAcC circuit after restraint stress in male and female rats, and explored the role of the endocannabinoid system. Male and female rats underwent 2 h of acute restraint stress. Behavioral tests and in vivo electrophysiological recordings were performed immediately and 24 h after stress exposure. cFos was performed immediately after stress. Since stress effects were observed only in males, we evaluated the systemic and intra-NAc blockade of CB1 receptors in male rats. We found increased c-Fos expression in the hypothalamus but not in the IC in both sexes after acute restraint stress, along with heightened anxiety and reduced exploratory behavior. Males and females exhibited different neuronal plasticity in the aIC-NAcC pathway. Under basal conditions, males showed equal proportions of long-term potentiation (LTP) and long-term depression (LTD), whereas females predominantly exhibited LTP. Stress disrupted synaptic plasticity in males by eliminating LTD in the aIC-NAcC pathway 24 h after exposure. This effect was reversed by systemic and local CB1 receptor blockade. These findings suggest that integration of aIC information into NAcC differs by sex, with stress-induced neuroplasticity changes occurring only in males, dependent on the endocannabinoid system. This study provides insight into sex differences in stress reactivity, which may relate to stress-related psychiatric disorders.

Projection-targeted photopharmacology reveals distinct anxiolytic roles for presynaptic mGluR2 in prefrontal- and insula-amygdala synapses

Dissecting how membrane receptors regulate neural circuits is critical for deciphering principles of neuromodulation and mechanisms of drug action. Here, we use a battery of optical approaches to determine how presynaptic metabotropic glutamate receptor 2 (mGluR2) in the basolateral amygdala (BLA) controls anxiety-related behavior in mice. Using projection-specific photopharmacological activation, we find that mGluR2-mediated presynaptic inhibition of ventromedial prefrontal cortex (vmPFC)-BLA, but not posterior insular cortex (pIC)-BLA, connections produces a long-lasting decrease in spatial avoidance. In contrast, presynaptic inhibition of pIC-BLA connections decreases social avoidance and novelty-induced hypophagia without impairing working memory, establishing this projection as a novel target for the treatment of anxiety disorders. Fiber photometry and viral mapping reveal distinct activity patterns and anatomical organization of vmPFC-BLA and pIC-BLA circuits. Together, this work reveals new aspects of BLA neuromodulation with therapeutic implications while establishing a powerful approach for optical mapping of drug action.

Neural circuits and therapeutic mechanisms of empathic pain

Empathy is the capacity to understand and share the experiences of others. This ability fosters connections between individuals, enriching the fabric of our shared world. One notable example is empathy for the pain of others. Such experiences facilitate the identification of potential dangers, both for oneself and for others. Neuroimaging studies have helped to pinpoint brain regions that modulate empathic pain. Recently, there has also been a surge in studies exploring the neural mechanisms of empathic pain in rodent models. Neuropsychiatric disorders such as autism, psychosis, and schizophrenia often exhibit empathy deficits. Targeting the modulation of empathic pain holds potential for alleviating core symptoms in these patients. Interestingly, empathy research may also benefit pain management, leading to new approaches for understanding the negative emotions associated with pain. This review summarizes recent advances in neuroimaging for the study of empathic pain, outlines the underlying neurocircuit mechanisms, describes therapeutic strategies, and explores promising avenues for future research. This article is part of the Special Issue on "Empathic Pain".

A posterior insula to lateral amygdala pathway transmits US-offset information with a limited role in fear learning

During fear learning, associations between a sensory cue (conditioned stimulus, CS) and an aversive stimulus (unconditioned stimulus, US) are formed in specific brain circuits. The lateral amygdala (LA) is involved in CS-US integration; however, US pathways to the LA remain understudied. Here, we investigated whether the posterior insular cortex (pInsCx), a hub for aversive state signaling, transmits US information to the LA during fear learning. We find that the pInsCx makes a robust, glutamatergic projection specifically targeting the anterior LA. In vivo Ca2+ imaging reveals that neurons in the pInsCx and anterior LA display US-onset and US-offset responses; imaging combined with axon silencing shows that the pInsCx selectively transmits US-offset information to the anterior LA. Optogenetic silencing, however, does not show a role for US-driven activity in the anterior LA or its pInsCx afferents in fear memory formation. Thus, we describe a cortical projection that carries US-offset information to the amygdala with a limited role in fear learning.

A SMARTTR workflow for multi-ensemble atlas mapping and brain-wide network analysis

In the last decade, activity-dependent strategies for labelling multiple immediate early gene (IEG) ensembles in mice have generated unprecedented insight into the mechanisms of memory encoding, storage, and retrieval. However, few strategies exist for brain-wide mapping of multiple ensembles, including their overlapping population, and none incorporate capabilities for downstream network analysis. Here, we introduce a scalable workflow to analyze traditionally coronally-sectioned datasets produced by activity-dependent tagging systems. Intrinsic to this pipeline is simple multi-ensemble atlas registration and statistical testing in R (SMARTTR), an R package which wraps mapping capabilities with functions for statistical analysis and network visualization, and support for import of external datasets. We demonstrate the versatility of SMARTTR by mapping the ensembles underlying the acquisition and expression of learned helplessness (LH), a robust stress model. Applying network analysis, we find that exposure to inescapable shock (IS), compared to context training (CT), results in decreased centrality of regions engaged in spatial and contextual processing and higher influence of regions involved in somatosensory and affective processing. During LH expression, the substantia nigra emerges as a highly influential region which shows a functional reversal following IS, indicating a possible regulatory function of motor activity during helplessness. We also report that IS results in a robust decrease in reactivation activity across a number of cortical, hippocampal, and amygdalar regions, indicating suppression of ensemble reactivation may be a neurobiological signature of LH. These results highlight the emergent insights uniquely garnered by applying our analysis approach to multiple ensemble datasets and demonstrate the strength of our workflow as a hypothesis-generating toolkit.

Zero-echo time imaging achieves whole brain activity mapping without ventral signal loss in mice

Functional MRI (fMRI) is an important tool for investigating functional networks. However, the widely used fMRI with T2*-weighted imaging in rodents has the problem of signal lack in the lateral ventral area of forebrain including the amygdala, which is essential for not only emotion but also noxious pain. Here, we scouted the zero-echo time (ZTE) sequence, which is robust to magnetic susceptibility and motion-derived artifacts, to image activation in the whole brain including the amygdala following the noxious stimulation to the hind paw. ZTE exhibited higher temporal signal-to-noise ratios than conventional fMRI sequences. Electrical sensory stimulation of the hind paw evoked ZTE signal increase in the primary somatosensory cortex. Formalin injection into the hind paw evoked early and latent change of ZTE signals throughout the whole brain including the subregions of amygdala. Furthermore, resting-state fMRI using ZTE demonstrated the functional connectivity, including that of the amygdala. These results indicate the feasibility of ZTE for whole brain fMRI including the amygdala and we first show acute and latent activity in different subnuclei of the amygdala complex after nociceptive stimulation.

Hindbrain networks: Exploring the hidden anxiety circuits in rodents

Anxiety disorders are multifaceted conditions that engage numerous brain regions and circuits. While the hindbrain is pivotal in fundamental biological functions, its role in modulating emotions has been underappreciated. This review will uncover critical targets and circuits within the hindbrain that are essential for both anxiety and anxiolytic effects, expanding on research obtained through behavioral tests. The bidirectional neural pathways between the hindbrain and other brain regions, with a spotlight on vagal afferent signaling, provide a crucial framework for unraveling the neural mechanisms underlying anxiety. Exploring neural circuits within the hindbrain can help to unravel the neurobiological mechanisms of anxiety and elucidate differences in the expression of these circuits between genders, thereby providing valuable insights for the development of future anxiolytic drugs.

Aberrant resting-state voxel-mirrored homotopic connectivity in major depressive disorder with and without anxiety

OBJECTIVE

Prior researchers have identified distinct differences in functional connectivity neuroimaging characteristics among MDD patients. However, the auxiliary diagnosis and subtype differentiation roles of VMHC values in MDD patients have yet to be fully understood. We aim to explore the separating ability of VMHC values in patients with anxious MDD or with non-anxious MDD and HCs.

METHODS

We recruited 90 patients with anxious MDD, 69 patients with non-anxious MDD and 84 HCs. We collected a set of clinical variables included HAMD-17 scores, HAMA scores and rs-fMRI data. The data were analyzed combining difference analysis, SVM, correlation analysis and ROC analysis.

RESULTS

Relative to HCs, non-anxious MDD patients displayed significant lower VMHC values in the insula and PCG, and anxious MDD patients displayed a significant decrease in VMHC values in the cerebellum_crus2, STG, postCG, MFG and IFG. Compared with non-anxious MDD patients, the anxious MDD showed significant enhanced VMHC values in the PCG. The VMHC values in the insula and cerebellum_crus2 regions showed a better ability to discriminate HCs from patients with non-anxious MDD or with anxious MDD. The VMHC values in PCG showed a better ability to discriminate patients with anxious MDD and non-anxious MDD patients.

CONCLUSION

The VMHC values in the insula and cerebellum_crus2 regions could be served as imaging markers to differentiate HCs from patients with non-anxious MDD or with anxious MDD respectively. And the VMHC values in the PCG could be used to discriminate patients with anxious MDD from the non-anxious MDD patients.

Identification of a stress-responsive subregion of the basolateral amygdala in male rats

The basolateral amygdala (BLA) is reliably activated by psychological stress and hyperactive in conditions of pathological stress or trauma; however, subsets of BLA neurons are also readily activated by rewarding stimuli and can suppress fear and avoidance behaviours. The BLA is highly heterogeneous anatomically, exhibiting continuous molecular and connectivity gradients throughout the entire structure. A critical gap remains in understanding the anatomical specificity of amygdala subregions, circuits, and cell types explicitly activated by acute stress and how they are dynamically activated throughout stimulus exposure. Using a combination of topographical mapping for the activity-responsive protein FOS and fiber photometry to measure calcium transients in real-time, we sought to characterize the spatial and temporal patterns of BLA activation in response to a range of novel stressors (shock, swim, restraint, predator odour) and non-aversive, but novel stimuli (crackers, citral odour). We report four main findings: (1) the BLA exhibits clear spatial activation gradients in response to novel stimuli throughout the medial-lateral and dorsal-ventral axes, with aversive stimuli strongly biasing activation towards medial aspects of the BLA; (2) novel stimuli elicit distinct temporal activation patterns, with stressful stimuli exhibiting particularly enhanced or prolonged temporal activation patterns; (3) changes in BLA activity are associated with changes in behavioural state; and (4) norepinephrine enhances stress-induced activation of BLA neurons via the ß-noradrenergic receptor. Moving forward, it will be imperative to combine our understanding of activation gradients with molecular and circuit-specificity.

Projections from subfornical organ to bed nucleus of the stria terminalis modulate inflammation-induced anxiety-like behaviors in mice

Peripheral inflammation is closely related to the pathogenesis of sickness behaviors and psychiatric disorders such as anxiety and depression. The circumventricular organs (CVOs) are important brain sites to perceive peripheral inflammatory signals, but few studies have reported their role in inflammation-induced anxiety or depression. Using a mouse model of lipopolysaccharide (LPS)-induced inflammation, we identified a previously unreported role of the subfornical organ (SFO), one of the CVOs, in combating inflammation-induced anxiety. LPS treatment induced anxiety-like and sickness behaviors in mice. Although both the SFO and the organum vasculosum of the lamina terminalis (a CVO) neurons were activated after LPS treatment, only manipulating SFO neurons modulated LPS-induced anxiety-like behaviors. Activating or inhibiting SFO neurons alleviated or aggravated LPS-induced anxiety-like behaviors. In addition, SFO exerted this effect through glutamatergic projections to the bed nucleus of the stria terminalis. Manipulating SFO neurons did not affect LPS-induced sickness behaviors. Thus, we uncovered an active role of SFO neurons in counteracting peripheral inflammation-induced anxiety.

Opposite-sex pairing alters social interaction-induced GCaMP and dopamine activity in the insular cortex of male prairie voles

The prairie vole (Microtus ochrogaster) is a monogamous rodent species which displays selective social behaviors to conspecifics after establishing a pair bonded relationship, specifically partner-directed affiliation and stranger-directed aggression. This social selectivity relies on the ability of an individual to respond appropriately to a social context and requires salience detection and valence assignment. The anterior insular cortex (aIC) has been implicated in stimulus processing and categorization across a variety of contexts and is well-situated to integrate environmental stimuli and internal affective states to modulate complex goal-directed behaviors and social decision-making. Surprisingly, the contribution of the aIC to the expression of pair bond-induced social selectivity in prairie voles has been drastically understudied. Here we examined whether neural activity and gene expression in the aIC change in response to opposite-sex pairing and/or as a function of pairing length in male prairie voles. Opposite-sex pairing was characterized by changes to calcium and dopamine (DA) transients in the aIC that corresponded with the display of social selectivity across pair bond maturation. Furthermore, D1 and D2 receptor mRNA expression was significantly higher in males after 48 hrs of cohabitation with a female partner compared to same-sex housed males, and D2 mRNA remained significantly higher in males with a female partner compared to same-sex housed males after a week of cohabitation. Together, these results implicate a role for DA and its receptors in the aIC across the transition from early- to late-phase pair bonding.

Chemogenetic inhibition of pain-related neurons in the posterior insula cortex reduces mechanical hyperalgesia and anxiety-like behavior during acute pain

Pain is a complex phenomenon that involves sensory, emotional, and cognitive components. The posterior insula cortex (pIC) has been shown to integrate multisensory experience with emotional and cognitive states. However, the involvement of the pIC in the regulation of affective behavior in pain remains unclear. Here, we investigate the role of pain-related pIC neurons in the regulation of anxiety-like behavior during acute pain. We combined a chemogenetic approach with targeted recombination in active populations (TRAP) in mice. Global chemogenetic inhibition of pIC neurons attenuates chemically-induced mechanical hypersensitivity without affecting pain-related anxiety-like behavior. In contrast, inhibition of pain-related pIC neurons reduces both mechanical hypersensitivity and pain-related anxiety-like behavior. The present study provides important insights into the role of pIC neurons in the regulation of sensory and affective pain-related behavior.

The Insular Cortex: An Interface Between Sensation, Emotion and Cognition

The insula is a complex brain region central to the orchestration of taste perception, interoception, emotion, and decision-making. Recent research has shed light on the intricate connections between the insula and other brain regions, revealing the crucial role of this area in integrating sensory, emotional, and cognitive information. The unique anatomical position and extensive connectivity allow the insula to serve as a critical hub in the functional network of the brain. We summarize its role in interoceptive and exteroceptive sensory processing, illustrating insular function as a bridge connecting internal and external experiences. Drawing on recent research, we delineate the insular involvement in emotional processes, highlighting its implications in psychiatric conditions, such as anxiety, depression, and addiction. We further discuss the insular contributions to cognition, focusing on its significant roles in time perception and decision-making. Collectively, the evidence underscores the insular function as a dynamic interface that synthesizes diverse inputs into coherent subjective experiences and decision-making processes. Through this review, we hope to highlight the importance of the insula as an interface between sensation, emotion, and cognition, and to inspire further research into this fascinating brain region.

The pivotal role of PACAP/PAC1R signaling from the anterior insular cortex to the locus coeruleus on anxiety-related behaviors of mice

The neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) and its specific receptor (PAC1R) are widely present in the central nervous system (CNS), and PACAP/PAC1R signaling has been implicated in anxiety-related behaviors. The locus coeruleus (LC), with its extensive noradrenergic (NA) projections throughout the CNS, is also implicated in anxiety. Although the LC exhibits a high expression of PAC1R, the precise role of PACAP/PAC1R signaling in the LC's involvement in anxiety remains unclear. Histochemical analysis confirmed high levels of PAC1R mRNA in the LC and showed that PAC1R gene transcripts were highly localized to NA neurons. Targeted deletion of PAC1R from these cells led to a hyperactive/low anxiety phenotype in the open field and elevated-plus maze tests. Retrograde neurocircuit tracing indicated PACAP neurons from the anterior insular cortex (aIC) and a few other regions projected axons to the LC. The selective activation of PACAP neurons in the aIC led to significantly increased anxiety behavior without a change in overall locomotor activity. Moreover, shRNA PACAP knockdown in the aIC in wild-type mice led to a selective decrease in anxiety. The present results identify an aIC to LC neurocircuit controlling anxiety that critically requires PACAP/PAC1R signaling.

Empathic pain: Exploring the multidimensional impacts of biological and social aspects in pain

Empathic pain refers to an individual's perception, judgment, and emotional response to others' pain. This complex social cognitive ability is crucial for healthy interactions in human society. In recent years, with the development of multidisciplinary research in neuroscience, psychology and sociology, empathic pain has become a focal point of widespread attention in these fields. However, the neural mechanism underlying empathic pain remain a controversial and unresolved area. This review aims to comprehensively summarize the history, influencing factors, neural mechanisms and pharmacological interventions of empathic pain. We hope to provide a comprehensive scientific perspective on how humans perceive and respond to others' pain experiences and to provide guidance for future research directions and clinical applications. This article is part of the Special Issue on "Empathic Pain".

Gestational CBD Shapes Insular Cortex in Adulthood

Many expectant mothers use CBD to alleviate symptoms like nausea, insomnia, anxiety, and pain, despite limited research on its long-term effects. However, CBD passes through the placenta, affecting fetal development and impacting offspring behavior. We investigated how prenatal CBD exposure affects the insular cortex (IC), a brain region involved in emotional processing and linked to psychiatric disorders. The IC is divided into two territories: the anterior IC (aIC), processing socioemotional signals, and the posterior IC (pIC), specializing in interoception and pain perception. Pyramidal neurons in the aIC and pIC exhibit sex-specific electrophysiological properties, including variations in excitability and the excitatory/inhibitory balance. We investigated IC's cellular properties and synaptic strength in the offspring of both sexes from mice exposed to low-dose CBD during gestation (E5-E18; 3 mg/kg, s.c.). Prenatal CBD exposure induced sex-specific and territory-specific changes in the active and passive membrane properties, as well as intrinsic excitability and the excitatory/inhibitory balance, in the IC of adult offspring. The data indicate that in utero CBD exposure disrupts IC neuronal development, leading to a loss of functional distinction between IC territories. These findings may have significant implications for understanding the effects of CBD on emotional behaviors in offspring.

Frontostriatal salience network expansion in individuals in depression

Decades of neuroimaging studies have shown modest differences in brain structure and connectivity in depression, hindering mechanistic insights or the identification of risk factors for disease onset1. Furthermore, whereas depression is episodic, few longitudinal neuroimaging studies exist, limiting understanding of mechanisms that drive mood-state transitions. The emerging field of precision functional mapping has used densely sampled longitudinal neuroimaging data to show behaviourally meaningful differences in brain network topography and connectivity between and in healthy individuals2-4, but this approach has not been applied in depression. Here, using precision functional mapping and several samples of deeply sampled individuals, we found that the frontostriatal salience network is expanded nearly twofold in the cortex of most individuals with depression. This effect was replicable in several samples and caused primarily by network border shifts, with three distinct modes of encroachment occurring in different individuals. Salience network expansion was stable over time, unaffected by mood state and detectable in children before the onset of depression later in adolescence. Longitudinal analyses of individuals scanned up to 62 times over 1.5 years identified connectivity changes in frontostriatal circuits that tracked fluctuations in specific symptoms and predicted future anhedonia symptoms. Together, these findings identify a trait-like brain network topology that may confer risk for depression and mood-state-dependent connectivity changes in frontostriatal circuits that predict the emergence and remission of depressive symptoms over time.

The Posterior Insular Cortex is Necessary for Feeding-Induced Jejunal Myoelectrical Activity in Male Rats

The gastrointestinal tract exhibits coordinated muscle motility in response to food digestion, which is regulated by the central nervous system through autonomic control. The insular cortex is one of the brain regions that may regulate the muscle motility. In this study, we examined whether, and how, the insular cortex, especially the posterior part, regulates gastrointestinal motility by recording jejunal myoelectrical signals in response to feeding in freely moving male rats. Feeding was found to induce increases in jejunal myoelectrical signal amplitudes. This increase in the jejunal myoelectrical signals was abolished by vagotomy and pharmacological inhibition of the posterior insular cortex. Additionally, feeding induced a decrease and increase in sympathetic and parasympathetic nervous activities, respectively, both of which were eliminated by posterior insular cortical inhibition. These results suggest that the posterior insular cortex regulates jejunal motility in response to feeding by modulating autonomic tone.

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.

Bidirectional fear modulation by discrete anterior insular circuits in male mice

The brain's ability to appraise threats and execute appropriate defensive responses is essential for survival in a dynamic environment. Humans studies have implicated the anterior insular cortex (aIC) in subjective fear regulation and its abnormal activity in fear/anxiety disorders. However, the complex aIC connectivity patterns involved in regulating fear remain under investigated. To address this, we recorded single units in the aIC of freely moving male mice that had previously undergone auditory fear conditioning, assessed the effect of optogenetically activating specific aIC output structures in fear, and examined the organization of aIC neurons projecting to the specific structures with retrograde tracing. Single-unit recordings revealed that a balanced number of aIC pyramidal neurons' activity either positively or negatively correlated with a conditioned tone-induced freezing (fear) response. Optogenetic manipulations of aIC pyramidal neuronal activity during conditioned tone presentation altered the expression of conditioned freezing. Neural tracing showed that non-overlapping populations of aIC neurons project to the amygdala or the medial thalamus, and the pathway bidirectionally modulated conditioned fear. Specifically, optogenetic stimulation of the aIC-amygdala pathway increased conditioned freezing, while optogenetic stimulation of the aIC-medial thalamus pathway decreased it. Our findings suggest that the balance of freezing-excited and freezing-inhibited neuronal activity in the aIC and the distinct efferent circuits interact collectively to modulate fear behavior.

Planar cell polarity proteins mediate ketamine-induced restoration of glutamatergic synapses in prefrontal cortical neurons in a mouse model for chronic stress

Single administration of low-dose ketamine has both acute and sustained anti-depressant effects. Sustained effect is associated with restoration of glutamatergic synapses in medial prefrontal cortic (mFPC) neurons. Ketamine induced profound changes in a number of molecular pathways in a mouse model for chronic stress. Cell-cell communication analyses predicted that planar-cell-polarity (PCP) signaling was decreased after chronic administration of corticosterone but increased following ketamine administration in most of the excitatory neurons. Similar decrease of PCP signaling in excitatory neurons was predicted in dorsolateral prefrontal cortical (dl-PFC) neurons of patients with major depressive disorder (MDD). We showed that the basolateral amygdala (BLA)-projecting infralimbic prefrontal cortex (IL PFC) neurons regulate immobility time in the tail suspension test and food consumption. Conditionally knocking out Celsr2 and Celsr3 or Prickle2 in the BLA-projecting IL PFC neurons abolished ketamine-induced synapse restoration and behavioral remission. Therefore, PCP proteins in IL PFC-BLA neurons mediate synapse restoration induced by of low-dose ketamine.

Alleviation of migraine related pain and anxiety by inhibiting calcium-stimulating AC1-dependent CGRP in the insula of adult rats

BACKGROUND

Recent animal and clinical findings consistently highlight the critical role of calcitonin gene-related peptide (CGRP) in chronic migraine (CM) and related emotional responses. CGRP antibodies and receptor antagonists have been approved for CM treatment. However, the underlying CGRP-related signaling pathways in the pain-related cortex remain poorly understood.

METHODS

The SD rats were used to establish the CM model by dural infusions of inflammatory soup. Periorbital mechanical thresholds were assessed using von-Frey filaments, and anxiety-like behaviors were observed via open field and elevated plus maze tests. Expression of c-Fos, CGRP and NMDA GluN2B receptors was detected using immunofluorescence and western blotting analyses. The excitatory synaptic transmission was detected by whole-cell patch-clamp recording. A human-used adenylate cyclase 1 (AC1) inhibitor, hNB001, was applied via insula stereotaxic and intraperitoneal injections in CM rats.

RESULTS

The insular cortex (IC) was activated in the migraine model rats. Glutamate-mediated excitatory transmission and NMDA GluN2B receptors in the IC were potentiated. CGRP levels in the IC significantly increased during nociceptive and anxiety-like activities. Locally applied hNB001 in the IC or intraperitoneally alleviated periorbital mechanical thresholds and anxiety behaviors in migraine rats. Furthermore, CGRP expression in the IC decreased after the hNB001 application.

CONCLUSIONS

Our study indicated that AC1-dependent IC plasticity contributes to migraine and AC1 may be a promising target for treating migraine in the future.

Cannabinoids regulate an insula circuit controlling water intake

The insular cortex, or insula, is a large brain region involved in the detection of thirst and the regulation of water intake. However, our understanding of the topographical, circuit, and molecular mechanisms for controlling water intake within the insula remains parcellated. We found that type-1 cannabinoid (CB1) receptors in the insular cortex cells participate in the regulation of water intake and deconstructed the circuit mechanisms of this control. Topographically, we revealed that the activity of excitatory neurons in both the anterior insula (aIC) and posterior insula (pIC) increases in response to water intake, yet only the specific removal of CB1 receptors in the pIC decreases water intake. Interestingly, we found that CB1 receptors are highly expressed in insula projections to the basolateral amygdala (BLA), while undetectable in the neighboring central part of the amygdala. Thus, we recorded the neurons of the aIC or pIC targeting the BLA (aIC-BLA and pIC-BLA) and found that they decreased their activity upon water drinking. Additionally, chemogenetic activation of pIC-BLA projection neurons decreased water intake. Finally, we uncovered CB1-dependent short-term synaptic plasticity (depolarization-induced suppression of excitation [DSE]) selectively in pIC-BLA, compared with aIC-BLA synapses. Altogether, our results support a model where CB1 receptor signaling promotes water intake by inhibiting the pIC-BLA pathway, thereby contributing to the fine top-down control of thirst responses.

Stereotyped goal-directed manifold dynamics in the insular cortex

The insular cortex is involved in diverse processes, including bodily homeostasis, emotions, and cognition. However, we lack a comprehensive understanding of how it processes information at the level of neuronal populations. We leveraged recent advances in unsupervised machine learning to study insular cortex population activity patterns (i.e., neuronal manifold) in mice performing goal-directed behaviors. We find that the insular cortex activity manifold is remarkably consistent across different animals and under different motivational states. Activity dynamics within the neuronal manifold are highly stereotyped during rewarded trials, enabling robust prediction of single-trial outcomes across different mice and across various natural and artificial motivational states. Comparing goal-directed behavior with self-paced free consumption, we find that the stereotyped activity patterns reflect task-dependent goal-directed reward anticipation, and not licking, taste, or positive valence. These findings reveal a core computation in insular cortex that could explain its involvement in pathologies involving aberrant motivations.

Converging Effects of Chronic Pain and Binge Alcohol Consumption on Anterior Insular Cortex Neurons Projecting to the Dorsolateral Striatum in Male Mice

Chronic pain and alcohol use disorder (AUD) are highly comorbid, and patients with chronic pain are more likely to meet the criteria for AUD. Evidence suggests that both conditions alter similar brain pathways, yet this relationship remains poorly understood. Prior work shows that the anterior insular cortex (AIC) is involved in both chronic pain and AUD. However, circuit-specific changes elicited by the combination of pain and alcohol use remain understudied. The goal of this work was to elucidate the converging effects of binge alcohol consumption and chronic pain on AIC neurons that send projections to the dorsolateral striatum (DLS). Here, we used the Drinking-in-the-Dark (DID) paradigm to model binge-like alcohol drinking in mice that underwent spared nerve injury (SNI), after which whole-cell patch-clamp electrophysiological recordings were performed in acute brain slices to measure intrinsic and synaptic properties of AIC→DLS neurons. In male, but not female, mice, we found that SNI mice with no prior alcohol exposure consumed less alcohol compared with sham mice. Electrophysiological analyses showed that AIC→DLS neurons from SNI-alcohol male mice displayed increased neuronal excitability and increased frequency of miniature excitatory postsynaptic currents. However, mice exposed to alcohol prior to SNI consumed similar amounts of alcohol compared with sham mice following SNI. Together, our data suggest that the interaction of chronic pain and alcohol drinking have a direct effect on both intrinsic excitability and synaptic transmission onto AIC→DLS neurons in mice, which may be critical in understanding how chronic pain alters motivated behaviors associated with alcohol.

Locus Coeruleus-Dorsolateral Septum Projections Modulate Depression-Like Behaviors via BDNF But Not Norepinephrine

Locus coeruleus (LC) dysfunction is involved in the pathophysiology of depression; however, the neural circuits and specific molecular mechanisms responsible for this dysfunction remain unclear. Here, it is shown that activation of tyrosine hydroxylase (TH) neurons in the LC alleviates depression-like behaviors in susceptible mice. The dorsolateral septum (dLS) is the most physiologically relevant output from the LC under stress. Stimulation of the LCTH -dLSSST innervation with optogenetic and chemogenetic tools bidirectionally can regulate depression-like behaviors in both male and female mice. Mechanistically, it is found that brain-derived neurotrophic factor (BDNF), but not norepinephrine, is required for the circuit to produce antidepressant-like effects. Genetic overexpression of BDNF in the circuit or supplementation with BDNF protein in the dLS is sufficient to produce antidepressant-like effects. Furthermore, viral knockdown of BDNF in this circuit abolishes the antidepressant-like effect of ketamine, but not fluoxetine. Collectively, these findings underscore the notable antidepressant-like role of the LCTH -dLSSST pathway in depression via BDNF-TrkB signaling.

The anterior insula and its projection to amygdala nuclei modulate the abstinence-exacerbated expression of conditioned place preference

RATIONALE

Relapse into substance use is often triggered by exposure to drug-related environmental cues. The magnitude of drug seeking depends on the duration of abstinence, a phenomenon known as the incubation of drug craving. Clinical and preclinical research shows that the insular cortex is involved in substance use disorders and cue-induced drug seeking. However, the role of the insula on memory retrieval and motivational integration for cue-elicited drug seeking remains to be determined.

OBJECTIVES

We investigated the role of the anterior insular cortex (aIC) and its glutamatergic projection to amygdala nuclei (aIC-AMY) on the expression of conditioned place preference (CPP) during early and late abstinence.

METHODS

Male adult C57BL/6J mice underwent amphetamine-induced CPP, and their preference was tested following 1 or 14 days of abstinence. aIC and aIC-AMY functional role in CPP expression was assessed at both abstinence periods by employing optogenetic silencing and behavioral pharmacology.

RESULTS

Compared to a single day, an exacerbated preference for the amphetamine-paired context was observed after 14 days of abstinence. Photoinhibition of either aIC or aIC-AMY projection reduced CPP expression following late but not early abstinence. Similarly, the antagonism of aIC NMDA receptors reduced CPP expression after 14 days of abstinence but not 1 day.

CONCLUSIONS

These results suggest that aIC and its glutamatergic output to amygdala nuclei constitute critical neurobiological substrates mediating enhanced motivational cue reactivity during the incubation of amphetamine craving rather than contextual memory recall. Moreover, cortical NMDA receptor signaling may become sensitized during abstinence, ultimately modulating disproportioned drug seeking.

Projection-Targeted Photopharmacology Reveals Distinct Anxiolytic Roles for Presynaptic mGluR2 in Prefrontal- and Insula-Amygdala Synapses

Dissecting how membrane receptors regulate neural circuit function is critical for deciphering basic principles of neuromodulation and mechanisms of therapeutic drug action. Classical pharmacological and genetic approaches are not well-equipped to untangle the roles of specific receptor populations, especially in long-range projections which coordinate communication between brain regions. Here we use viral tracing, electrophysiological, optogenetic, and photopharmacological approaches to determine how presynaptic metabotropic glutamate receptor 2 (mGluR2) activation in the basolateral amygdala (BLA) alters anxiety-related behavior. We find that mGluR2-expressing neurons from the ventromedial prefrontal cortex (vmPFC) and posterior insular cortex (pIC) preferentially target distinct cell types and subregions of the BLA to regulate different forms of avoidant behavior. Using projection-specific photopharmacological activation, we find that mGluR2-mediated presynaptic inhibition of vmPFC-BLA, but not pIC-BLA, connections can produce long-lasting decreases in spatial avoidance. In contrast, presynaptic inhibition of pIC-BLA connections decreased social avoidance, novelty-induced hypophagia, and increased exploratory behavior without impairing working memory, establishing this projection as a novel target for the treatment of anxiety disorders. Overall, this work reveals new aspects of BLA neuromodulation with therapeutic implications while establishing a powerful approach for optical mapping of drug action via photopharmacology.

Emotion in action: When emotions meet motor circuits

The brain is a remarkably complex organ responsible for a wide range of functions, including the modulation of emotional states and movement. Neuronal circuits are believed to play a crucial role in integrating sensory, cognitive, and emotional information to ultimately guide motor behavior. Over the years, numerous studies employing diverse techniques such as electrophysiology, imaging, and optogenetics have revealed a complex network of neural circuits involved in the regulation of emotional or motor processes. Emotions can exert a substantial influence on motor performance, encompassing both everyday activities and pathological conditions. The aim of this review is to explore how emotional states can shape movements by connecting the neural circuits for emotional processing to motor neural circuits. We first provide a comprehensive overview of the impact of different emotional states on motor control in humans and rodents. In line with behavioral studies, we set out to identify emotion-related structures capable of modulating motor output, behaviorally and anatomically. Neuronal circuits involved in emotional processing are extensively connected to the motor system. These circuits can drive emotional behavior, essential for survival, but can also continuously shape ongoing movement. In summary, the investigation of the intricate relationship between emotion and movement offers valuable insights into human behavior, including opportunities to enhance performance, and holds promise for improving mental and physical health. This review integrates findings from multiple scientific approaches, including anatomical tracing, circuit-based dissection, and behavioral studies, conducted in both animal and human subjects. By incorporating these different methodologies, we aim to present a comprehensive overview of the current understanding of the emotional modulation of movement in both physiological and pathological conditions.

Recent advances in anxiety disorders: Focus on animal models and pathological mechanisms

Anxiety disorders have become one of the most severe psychiatric disorders, and the incidence is increasing every year. They impose an extraordinary personal and socioeconomic burden. Anxiety disorders are influenced by multiple complex and interacting genetic, psychological, social, and environmental factors, which contribute to disruption or imbalance in homeostasis and eventually cause pathologic anxiety. The selection of a suitable animal model is important for the exploration of disease etiology and pathophysiology, and the development of new drugs. Therefore, a more comprehensive understanding of the advantages and limitations of existing animal models of anxiety disorders is helpful to further study the underlying pathological mechanisms of the disease. This review summarizes animal models and the pathogenesis of anxiety disorders, and discusses the current research status to provide insights for further study of anxiety disorders.