The central amygdala (CeA) is involved in opioid relapse-associated behaviors. This study determined if escalation of fentanyl intake as modeled by long-access (LgA) self-administration (SA) alters ex vivo neuronal activity in CeA in response to fentanyl during acute withdrawal and protracted abstinence. Adult male and female Sprague-Dawley rats were trained to self-administer fentanyl or saline across 7 daily 1-h short access (ShA) sessions, followed by 21 6-h long access (LgA) sessions. Following acute (17 h) or protracted (30 days) withdrawal, withdrawal signs were assessed and rats were euthanized for CeA calcium imaging in brain slices. Fentanyl rats demonstrated reduced basal frequency of activity after 30 days withdrawal, but not after 17 h withdrawal. Regardless of SA group, acute fentanyl application in slices reduced activity (frequency, duration, active cell number) of CeA neurons. In acute withdrawal, the magnitude to which acute fentanyl suppressed CeA neuronal activity was smaller in fentanyl SA rats, relative to saline SA controls. However, the magnitude of acute fentanyl effect on suppression of CeA activity was greater in fentanyl SA rats (vs. saline SA controls) after protracted abstinence.

Sleep, a state of reduced responsiveness and distinct brain activity, is crucial across the animal kingdom. This review explores the potential adaptive functions of REM sleep in adapting to stress, emphasizing its role in memory consolidation, emotional regulation, and threat processing. We further explore the underlying neural mechanisms linking stress responses to REM sleep. By synthesizing current findings, we propose that REM sleep allows animals to "rehearse" or simulate responses to danger in a secure, offline state, while also maintaining emotional balance. Environmental factors, such as predation risk and social dynamics, further influence REM sleep. This modulation may enhance survival by optimizing stress responses while fulfilling physiological needs in animals. Insights into REM sleep's role in animals may shed light on human sleep in the context of modern stressors and sleep disruptions. This review also explores the complex interplay between stress, immunity, sleep disruptions-particularly involving REM sleep-and their evolutionary underpinnings.

It is currently estimated that every 15 minutes an infant is born with opioid use disorder and undergoes intense early life trauma due to opioid withdrawal. Clinical research on the long-term consequences of gestational opioid exposure reports increased rates of social, conduct, and emotional disorders in these children. Here, we investigate the impact of perinatal opioid exposure (POE) on behaviors associated with anhedonia and stress in male and female Sprague Dawley rats. Young adult female rats were administered morphine via programmable, subcutaneous micro-infusion pumps before, during, and through one week post gestation. For the first two postnatal weeks, maternal behavior was examined for fragmentation and unpredictability. Unpredictable behavioral patterns were quantitatively characterized as entropy scores. Offspring were assessed for sucrose preference, social behavior, and stress responsivity. Overall, dams that received morphine across gestation displayed significantly less pup-directed behavior with increased fragmentation for nursing and higher entropy scores. In adolescence, male and female rat offspring exposed to morphine displayed reduced sucrose preference and, as adults, spent significantly less time interacting with familiar conspecifics. Changes in social behaviors were linked to increased activity in nondopaminergic cells of mesolimbic reward brain regions. Although no treatment effects were observed in forced swim test performance, corticosterone levels were significantly increased in POE adult males. Together, these results suggest that perinatal morphine exposure promotes anhedonic behavior, possibly due to fragmented and unpredictable maternal behavior in opioid-dependent dams.

Understanding how threats drive fear memory formation is crucial to understanding how organisms adapt to environments and treat threat-related disorders such as PTSD. While traditional Pavlovian conditioning studies have provided valuable insights, the exclusive reliance on electric shock as a threat stimulus has limited our understanding of diverse threats. To address this, we developed a conditioning paradigm using a looming visual stimulus as an unconditioned stimulus (US) in mice and identified a distinct neural circuit for visual threat conditioning. Parabrachial CGRP neurons were necessary for both conditioning and memory retrieval. Upstream neurons in the posterior insular cortex (pIC) responded to looming stimuli, and their projections to the parabrachial nucleus (PBN) induced aversive states and drove conditioning. However, this pIC-to-PBN pathway was not required for foot-shock conditioning. These findings reveal how non-nociceptive visual stimuli can drive aversive states and fear memory formation, expanding our understanding of aversive US processing beyond traditional models.

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.

Dopamine release in the nucleus accumbens (NAc) plays a critical role in the motivation to perform actions that promote survival. However, the NAc dopamine response to innately threatening visual stimuli, such as predators descending from above, and the innate behaviors they promote has not been fully characterized. Using the genetically encoded sensor dLight1, we investigated looming visual threat-evoked dopamine release in the lateral (LNAc) and medial NAc shell (NAcS) regions in freely moving mice during performance of a looming stimulus assay. We found that dopamine release related to visual threat perception in the NAcS, but not in the LNAc, predicts the timing and vigor of a future defensive action, yet dopamine released during the performance of the action itself does not. Optogenetic inhibition of dopaminergic terminals in the NAcS at visual stimulus onset prevented escape, confirming a role for ventral striatal dopamine in promoting threat-related behaviors.

Autism Spectrum Disorder (ASD) is characterized by impairments in social interaction and repetitive behaviors. A key characteristic of ASD is a decreased interest in social interactions, which affects individuals' ability to engage with their social environment. This study explores the neurobiological basis of these social deficits, focusing on the pathway between the Superior Colliculus (SC) and the Ventral Tegmental Area (VTA). Adopting a translational approach, our research used Shank3 knockout mice (Shank3-/-), which parallel a clinical cohort of young children with ASD, to investigate these mechanisms. We observed consistent deficits in social orienting across species. In children with ASD, fMRI analyses revealed a significant decrease in connectivity between the SC and VTA. Additionally, using miniscopes in mice, we identified a reduction in the frequency of calcium transients in SC neurons projecting to the VTA, accompanied by changes in neuronal correlation and intrinsic cellular properties. Notably, the interneuronal correlation in Shank3-/- mice and the functional connectivity of the SC to VTA pathway in children with ASD correlated with the severity of social deficits. Our findings underscore the potential of the SC-VTA pathway as a biomarker for ASD and open new avenues for therapeutic interventions, highlighting the importance of early detection and targeted treatment strategies.

Dopaminergic (DA) neurons of the substantia nigra pars compacta (SNc) and ventral tegmental area (VTA) play a crucial role in controlling animals' orienting and approach behaviors toward relevant environmental stimuli. The ventral midbrain receives sensory input from the superior colliculus (SC), a tectal region that processes information from contralateral receptive fields of various modalities. Given the significant influence of dopamine release imbalance in the left and right striatum on animals' movement direction, our study aimed to investigate the lateralization of the connection between the lateral SC and the midbrain DA system in male rats. We explored the circuit's anatomy using transsynaptic viral tract-tracing and its physiology using in vivo single-unit and ex vivo multi-electrode array recordings of SNc and VTA neuronal activity combined with optogenetic stimulation of either the ipsilateral or contralateral SC or its terminals. During the experiments, DA neurons were identified optogenetically (in vivo recordings) or pharmacologically (ex vivo recordings). Anatomical findings revealed a bilateral innervation pattern of the lateral SC to the ventral midbrain, with a significantly stronger ipsilateral connection, particularly evident in the SNc, involving both DA and non-DA neurons. This anatomical asymmetry was also expressed during in vivo and ex vivo recordings, which showed a predominance of ipsilateral connections, especially within the SNc. Ex vivo recordings also confirmed that this lateralized pathway is direct. The described features of the SC→VTA/SNc neuronal circuit, particularly its anatomical and physiological asymmetry, suggest its involvement in orienting and approach behaviors guided by the direction of incoming sensory stimuli.

The mesolimbic dopamine system is a set of subcortical brain circuits that plays a key role in reward processing, reinforcement, associative learning, and behavioral responses to salient environmental events. In our previous studies of the dopaminergic response to salient visual stimuli, we observed that dopamine release in the lateral nucleus accumbens (LNAc) of mice encoded information about the rate and magnitude of rapid environmental luminance changes from darkness. Light-evoked dopamine responses were rate-dependent, robust to the time of testing or stimulus novelty, and required phototransduction by rod and cone opsins. However, it is unknown if these dopaminergic responses also involve non-visual opsins, such as melanopsin, the primary photopigment expressed by intrinsically photosensitive retinal ganglion cells (ipRGCs). In the current study, we evaluated the role of melanopsin in the dopaminergic response to light in the LNAc using the genetically encoded dopamine sensor dLight1 and fiber photometry. By measuring light-evoked dopamine responses across a broad irradiance and wavelength range in constitutive melanopsin (Opn4) knockout mice, we were able to provide new insights into the ability of non-visual opsins to regulate the mesolimbic dopamine response to visual stimuli.

Neuronal plasticity in the central amygdala (CeA) is essential for modulating feeding behaviors and emotional responses, potentially influencing reactions to Deoxynivalenol (DON). Acute oral administration of DON elicits a dose-responsive reduction in food intake, accompanied by pronounced alterations in locomotor activity and feeding frequency. This study investigates circuitry adaptations that mediate DON's effects on feeding, by targeting of GABA neurons in the CeA. Following exposure to DON, an increase in connectivity between the paraventricular nucleus of the thalamus (PVT) and CeAGABA neurons is observed, suggesting the involvement of this pathway in DON's adverse effects on feeding and emotional states. Chemogenetic and optogenetic manipulations of CeAGABA neurons resulted in substantial alterations in mice's feeding and overall activity. These findings suggest that CeAGABA neurons are involved in DON-induced anorexia and aversive-like emotional responses. Additionally, the administration of the SCN10A antagonist (A-803467) effectively mitigated DON-induced anorexia and aversive-like emotions, highlighting the pivotal role of the PVT-CeA circuit and CeAGABA neurons in regulating the physiological and emotional impacts of DON. These findings have significant implications for public health and clinical interventions, offering potential therapeutic strategies to mitigate DON's adverse effects on human health.

While Virtual Reality (VR) technology shows promise in the management of substance use disorders, the development of an effective VR-based extinction procedure remains lacking. In this study, we developed a VR-based eye movement desensitization and reprocessing extinction training program tailored for mice. We found that this VR treatment during cocaine extinction prevents reinstatement by suppressing the hyperactivation of glutamatergic excitatory neurons in the intermediate layers of the superior colliculus (SCiCaMKIIα) during exposure to environmental cues. Additionally, SCiCaMKIIα neurons innervate tyrosine hydroxylase-positive neurons in the locus coeruleus (LCTH). Environmental cues trigger stronger phasic activation of LCTH neurons through this SCiCaMKIIα→LCTH projection, leading to increased dopamine release onto the dorsal CA3 (dCA3) region, thereby facilitating reinstatement. Furthermore, we demonstrate that VR treatment effectively inhibits the neural circuitry involving SCiCaMKIIα→LCTH→dCA3 in response to environmental cues, thus preventing cocaine reinstatement. Our findings suggest that VR treatment may represent a promising strategy for achieving drug abstinence.

The superior colliculus (SC) is the main brain region regulating defensive behaviors to visual threats. Yet, how the SC integrates binocular visual information and to what extent binocular vision drives defensive behaviors remains unknown. Here, we show that SC neurons respond to binocular visual input with diverse synaptic and spiking responses, summating visual inputs largely sublinearly. Using pathway-specific optogenetic silencing, we find that contralateral and ipsilateral visual information is carried to binocular SC neurons through retinal, interhemispheric, and corticotectal pathways. These pathways carry binocular visual input to the SC in a layer-specific manner, with superficial layers receiving visual information through retinal input, whereas intermediate and deep layers rely on interhemispheric and corticotectal pathways. We further show that binocular vision facilitates visually evoked escape behavior. Together, our data shed light on the cellular and circuit mechanisms underlying binocular visual processing in the SC and its role in defensive behaviors to visual threats.

Depressive disorders, including major depressive disorder (MDD), represent one of the most prevalent set of disorders worldwide. MDD is characterized by a range of cognitive, behavioral, and neurobiological changes that contribute to the vast array of symptom profiles that make this disorder particularly difficult to treat. A multitude of established evidence suggests a role for the dopamine system, stemming in part from the ventral tegmental area (VTA), in mediating symptoms and behavioral changes that underlie depression. Developments in cutting-edge technologies in pre-clinical models of depressive phenotypes, such as retrograde tracing, electrophysiological recordings, immunohistochemistry, and molecular profiling, have allowed a deeper characterization of singular VTA neuron molecular, physiological, and projection properties. These developments have highlighted that the VTA is not a homogenous cell population but instead comprises vast cellular diversity that underscores its modular role across various functions related to reward processing, aversion, salience processing, learning and motivation. In this review, we begin by introducing the various cell types and brain regions that comprise the VTA circuitry. Then, we introduce the role of the VTA in reward processing as it compares to aversion processing. Next, we characterize distinct neural pathways within the VTA circuitry to understand the effects of chronic social and non-social stress and tie together how these neurobiological changes manifest into specific behavioral phenotypes. Finally, we relate these preclinical findings to clinical findings to parse the heterogeneity of depressive phenotypes and explain the efficacy of recent novel pharmacological interventions that may target the VTA in MDD.

Defense or death presents a canonical dilemma for animals when encountering predators. Threatening sensory cues provide essential information that signals predator presence, driving the evolution of a spectrum of defensive behaviors. In rodents, these behaviors, as described by the classic "predatory imminence continuum" model, range from risk assessment and freezing to rapid escape responses. During the pre-encounter phase, risk assessment and avoidance responses are crucial for monitoring the environment with vigilance and cautiousness. Once detected during the post-encounter phase or physically attacked during the circa-strike phase, multiple sensory systems are rapidly activated, triggering escape responses to increase the distance from the threat. Although there are species-specific variations, the brain regions underpinning these defensive strategies, including the thalamus, hypothalamus, and midbrain, are evolutionarily conserved. This review aims to provide a comprehensive overview of the universal innate defensive circuit framework to enrich our understanding of how animals respond to life-threatening situations.

The ventral tegmental area (VTA), a midbrain region associated with motivated behaviors, contains mostly dopaminergic (DA) neurons and GABAergic (GABA) neurons. Previous work has suggested that VTA GABA neurons provide a reward prediction signal, which is used in computing a reward prediction error. In this study, by using in vivo electrophysiology and continuous quantification of force exertion in head-fixed mice, we identify distinct populations of VTA GABA neurons that exhibit precise force tuning independently of learning, reward prediction, and outcome valence. Their activity usually precedes force exertion, and selective optogenetic manipulations of these neurons systematically modulate force exertion without influencing reward prediction. Together, these findings show that VTA GABA neurons can continuously regulate force vectors during motivated behavior.

Daily life for humans and other animals requires switching between periods of threat- and reward-oriented behavior. We investigated neural activity associated with spontaneous switching, in a naturalistic task, between foraging for rewards and seeking information about potential threats with 7T fMRI in healthy humans. Switching was driven by estimates of likelihood of threat and reward. Both tracking of threat and switching to a vigilant mode in which people sought more information about potential threats were associated with specific but distributed patterns of activity spanning habenula, dorsal raphe nucleus (DRN), anterior cingulate cortex, and anterior insula cortex. Different aspects of the distributed activity patterns were linked to monitoring the threat level, seeking information about the threat, and actual threat detection. A distinct pattern of activity in the same circuit and elsewhere occurred during returns to reward-oriented behavior. Individual variation in DRN activity reflected individual variation in the seeking of information about threats.

GABAergic neurons in mouse ventral tegmental area (VTA) exhibit elevated activity during withdrawal following chronic ethanol exposure. While increased glutamatergic input and decreased GABAA receptor sensitivity have been implicated, the impact of inhibitory signaling in VTA GABA neurons has not been fully addressed.

We used electrophysiological and ultrastructural approaches to assess the impact of chronic intermittent ethanol vapour exposure in mice on GABAergic transmission in VTA GABA neurons during withdrawal. We used CRISPR/Cas9 ablation to mimic a somatodendritic adaptation involving the GABAB receptor (GABABR) in ethanol-naïve mice to investigate its impact on anxiety-related behaviour.

The frequency of spontaneous inhibitory postsynaptic currents was reduced in VTA GABA neurons following chronic ethanol treatment and this was reversed by GABABR inhibition, suggesting chronic ethanol strengthens the GABABR-dependent suppression of GABAergic input to VTA GABA neurons. Similarly, paired-pulse depression of GABAA receptor-dependent responses evoked by optogenetic stimulation of nucleus accumbens inputs from ethanol-treated mice was reversed by GABABR inhibition. Somatodendritic currents evoked in VTA GABA neurons by GABABR activation were reduced following ethanol exposure, attributable to the suppression of GIRK (Kir3) channel activity. Mimicking this adaptation enhanced anxiety-related behaviour in ethanol-naïve mice.

Chronic ethanol weakens the GABAergic regulation of VTA GABA neurons in mice via pre- and postsynaptic mechanisms, likely contributing to their elevated activity during withdrawal and expression of anxiety-related behaviour. As anxiety can promote relapse during abstinence, interventions targeting VTA GABA neuron excitability could represent new therapeutic strategies for treatment of alcohol use disorder.

It is currently estimated that every 15 minutes an infant is born with opioid use disorder and undergoes intense early life trauma due to opioid withdrawal. Clinical research on the long-term consequences of gestational opioid exposure reports increased rates of social, conduct, and emotional disorders in these children. Here, we investigate the impact of perinatal opioid exposure (POE) on behaviors associated with anhedonia and stress in male and female Sprague Dawley rats. Young adult female rats were administered morphine via programmable, subcutaneous micro-infusion pumps before, during, and through one week post gestation. Maternal behavior was examined for fragmentation and entropy for the first two postnatal weeks; offspring were assessed for sucrose preference, social behavior, and stress responsivity. Overall, dams that received morphine across gestation displayed significantly less pup-directed behavior with increased fragmentation for nursing and higher entropy scores. In adolescence, male and female rat offspring exposed to morphine displayed reduced sucrose preference and, as adults, spent significantly less time socially interacting with familiar conspecifics. Changes in social behaviors were linked to increased activity in nondopaminergic mesolimbic reward brain regions. Although no treatment effects were observed in forced swim test performance, corticosterone levels were significantly increased in POE adult males. Together, these results suggest that perinatal morphine exposure results in anhedonic behavior, possibly due to fragmented and unpredictable maternal behavior in opioid-dependent dams.

The ventral tegmental area (VTA), a midbrain region associated with motivated behaviors, consists predominantly of dopaminergic (DA) neurons and GABAergic (GABA) neurons. Previous work has suggested that VTA GABA neurons provide a reward prediction, which is used in computing a reward prediction error. In this study, using in vivo electrophysiology and continuous quantification of force exertion in head-fixed mice, we discovered distinct populations of VTA GABA neurons that exhibited precise force tuning independently of learning, reward prediction, and outcome valence. Their activity usually preceded force exertion, and selective optogenetic manipulations of these neurons systematically modulated force exertion without influencing reward prediction. Together, these findings show that VTA GABA neurons continuously regulate force vectors during motivated behavior.

The looming stimulus-evoked flight response to approaching predators is a defensive behavior in most animals. However, how looming stimuli are detected in the retina and transmitted to the brain remains unclear. Here, we report that a group of GABAergic retinal ganglion cells (RGCs) projecting to the superior colliculus (SC) transmit looming signals from the retina to the brain, mediating the looming-evoked flight behavior by releasing GABA. GAD2-Cre and vGAT-Cre transgenic mice were used in combination with Cre-activated anterograde or retrograde tracer viruses to map the inputs to specific GABAergic RGC circuits. Optogenetic technology was used to assess the function of SC-projecting GABAergic RGCs (scpgRGCs) in the SC. FDIO-DTA (Flp-dependent Double-Floxed Inverted Open reading frame-Diphtheria toxin) combined with the FLP (Florfenicol, Lincomycin & Prednisolone) approach was used to ablate or silence scpgRGCs. In the mouse retina, GABAergic RGCs project to different brain areas, including the SC. ScpgRGCs are monosynaptically connected to parvalbumin-positive SC neurons known to be required for the looming-evoked flight response. Optogenetic activation of scpgRGCs triggers GABA-mediated inhibition in SC neurons. Ablation or silencing of scpgRGCs compromises looming-evoked flight responses without affecting image-forming functions. Our study reveals that scpgRGCs control the looming-evoked flight response by regulating SC neurons via GABA, providing novel insight into the regulation of innate defensive behaviors.

Visual system is the most important system of animal to cognize the information in outside world, and reward-related visual cues are the key factors in the consolidation and retrieval of reward memory. However, the neural circuit mechanism is still unclear. Superior Colliculus (SC) receive direct input from the retina and belong to the earliest stages of visual processing. Recent studies identified a specific pathway from SC to ventral tegmental area (VTA) that underlie specific innate behaviors, eg. flight or freezing, approach behaviors and so on. In present research, we investigated that inhibition of SC to VTA circuit with chemogenetics suppressed light cue-associated reward-seeking behaviors, while activation of the SC-VTA circuit with chemogenetic technology triggered the reward-seeking behaviors in optical intracranial self-stimulation for VTA DA neurons (oICSS) in mice. These findings suggest that neural circuit of SC-VTA mediates the retrieval of reward memory associated with visual cues, which will provide a new field for revealing the neural mechanism of pathological memory such as addiction.

The superior colliculus (SC) is a conserved midbrain structure that is important for transforming visual and other sensory information into motor actions. Decades of investigations in numerous species have made the SC and its nonmammalian homologue, the optic tectum, one of the best studied structures in the brain, with rich information now available regarding its anatomical organization, its extensive inputs and outputs and its important functions in many reflexive and cognitive behaviours. Excitingly, recent studies using modern genomic and physiological approaches have begun to reveal the diverse neuronal subtypes in the SC, as well as their unique functions in visuomotor transformation. Studies have also started to uncover how subtypes of SC neurons form intricate circuits to mediate visual processing and visually guided behaviours. Here, we review these recent discoveries on the cell types and neuronal circuits underlying visuomotor transformations mediated by the SC. We also highlight the important future directions made possible by these new developments.

Spatial memories guide navigation efficiently toward desired destinations. However, the neuronal and circuit mechanisms underlying the encoding of goal locations and its translation into goal-directed navigation remain unclear. Here we demonstrate that mice rapidly form a spatial memory of a shelter during shelter experiences, guiding escape behavior toward the goal location-a shelter-when under threat. Dopaminergic neurons in the ventral tegmental area and their projection to the nucleus accumbens (NAc) encode safety signals associated with the shelter. Optogenetically induced phasic dopamine signals are sufficient to create a place memory that directs escape navigation. Converging dopaminergic and hippocampal glutamatergic inputs to the NAc mediate the formation of a goal-related memory within a subpopulation of NAc neurons during shelter experiences. Artificial co-activation of this goal-related NAc ensemble with neurons in the dorsal periaqueductal gray was sufficient to trigger memory-guided, rather than random, escape behavior. These findings provide causal evidence of cognitive circuit modules linking memory with goal-directed action.

Innate defensive behaviors are essential for species survival. While these behaviors start to develop early in an individual's life, there is still much to be understood about how they evolve with advancing age. Considering that aging is often accompanied by various cognitive and physical declines, we tested the hypothesis that innate fear behaviors and underlying cerebral mechanisms are modified by aging. In our study we investigated this hypothesis by examining how aged mice respond to a looming visual threat compared to their younger counterparts. Our findings indicate that aged mice exhibit a different fear response than young mice when facing this imminent threat. Specifically, unlike young mice, aged mice tend to predominantly display freezing behavior without seeking shelter. Interestingly, this altered behavioral response in aged mice is linked to a distinct pattern of functional brain connectivity compared to young mice. Notably, our data highlights a lack of a consistent brain activation following the fear response in aged mice, suggesting that innate defensive behaviors undergo changes with aging.

The selection of appropriate defensive behaviors in the face of potential threat is fundamental to survival. However, after repeated exposures to threatening stimuli that did not signal real danger, an animal must learn to adjust and optimize defensive behaviors. Despite extensive research on innate threat processing, little is known how individuals change their defensive behaviors when presented with recurrent threat exposures without evidence of a real risk. Insight into this process is critical as its dysregulation may contribute to neuropsychiatric conditions, such as anxiety disorders. Here, we used the visual looming stimulus (VLS) paradigm in mice to investigate innate threat processing and adaptive defensive learning. Repeated exposure to VLS over consecutive sessions reduced immediate freezing responses and time spent inside a sheltered area upon VLS events, leading to an increase in foraging behaviors. Fiber photometry recordings and optogenetic manipulations revealed that VLS innate adaptive defensive learning is associated with reduced recruitment of the midbrain interpeduncular nucleus (IPN), a structure associated with fear and anxiety-related behaviors. Functional circuit-mapping identified a role for select IPN projections to the laterodorsal tegmental nucleus in gating defensive learning. Finally, we uncovered a subpopulation of IPN neurons that express the neuropeptide somatostatin and encode safety- and avoidance signals in response to VLS. These results identify critical behavioral signatures of innate defensive responses and a circuit that regulates the essential features of threat processing.

Effective detection and avoidance from environmental threats are crucial for animals' survival. Integration of sensory cues associated with threats across different modalities can significantly enhance animals' detection and behavioral responses. However, the neural circuit-level mechanisms underlying the modulation of defensive behavior or fear response under simultaneous multimodal sensory inputs remain poorly understood. Here, we report in mice that bimodal looming stimuli combining coherent visual and auditory signals elicit more robust defensive/fear reactions than unimodal stimuli. These include intensified escape and prolonged hiding, suggesting a heightened defensive/fear state. These various responses depend on the activity of the superior colliculus (SC), while its downstream nucleus, the parabigeminal nucleus (PBG), predominantly influences the duration of hiding behavior. PBG temporally integrates visual and auditory signals and enhances the salience of threat signals by amplifying SC sensory responses through its feedback projection to the visual layer of the SC. Our results suggest an evolutionarily conserved pathway in defense circuits for multisensory integration and cross-modality enhancement.

Pavlovian fear conditioning research suggests that the interaction between the dorsal periaqueductal gray (dPAG) and basolateral amygdala (BLA) acts as a prediction error mechanism in the formation of associative fear memories. However, their roles in responding to naturalistic predatory threats, characterized by less explicit cues and the absence of reiterative trial-and-error learning events, remain unexplored. In this study, we conducted single-unit recordings in rats during an 'approach food-avoid predator' task, focusing on the responsiveness of dPAG and BLA neurons to a rapidly approaching robot predator. Optogenetic stimulation of the dPAG triggered fleeing behaviors and increased BLA activity in naive rats. Notably, BLA neurons activated by dPAG stimulation displayed immediate responses to the robot, demonstrating heightened synchronous activity compared to BLA neurons that did not respond to dPAG stimulation. Additionally, the use of anterograde and retrograde tracer injections into the dPAG and BLA, respectively, coupled with c-Fos activation in response to predatory threats, indicates that the midline thalamus may play an intermediary role in innate antipredatory-defensive functioning.

Alcohol is the most widely used addictive substance, potentially leading to brain damage and genetic abnormalities. Despite its prevalence and associated risks, current treatments have yet to identify effective methods for reducing cravings and preventing relapse. In this study, we find that 4-Hz alternating bilateral sensory stimulation (ABS) effectively reduces ethanol-induced conditioned place preference (CPP) in male mice, while 4-Hz flash light does not exhibit therapeutic effects. Whole-brain c-Fos mapping demonstrates that 4-Hz ABS triggers notable activation in superior colliculus GABAergic neurons (SCGABA). SCGABA forms monosynaptic connections with ventral tegmental area dopaminergic neurons (VTADA), which is implicated in ethanol-induced CPP. Bidirectional chemogenetic manipulation of SC-VTA circuit either replicates or blocks the therapeutic effects of 4-Hz ABS on ethanol-induced CPP. These findings elucidate the role of SC-VTA circuit for alleviating ethanol-related CPP by 4-Hz ABS and point to a non-drug and non-invasive approach that might have potential for treating alcohol use disorder.

Stress and trauma are significant risk factors for many neuropsychiatric disorders and diseases, including anxiety disorders. Stress-induced anxiety symptoms have been attributed to enhanced excitability in circuits controlling fear, anxiety, and aversion. A growing body of evidence has implicated GABAergic neurons of the ventral tegmental area (VTA) in aversion processing and affective behavior.

We used an unpredictable footshock (uFS) model, together with electrophysiological and behavioral approaches, to investigate the role of VTA GABA neurons in anxiety-related behavior in mice.

One day after a single uFS session, C57BL/6J mice exhibited elevated anxiety-related behavior and VTA GABA neuron excitability. The enhanced excitability of VTA GABA neurons was correlated with increased glutamatergic input and a reduction in postsynaptic signaling mediated via GABAA and GABAB receptors. Chemogenetic activation of VTA GABA neurons was sufficient to increase anxiety-related behavior in stress-naïve mice. In addition, chemogenetic inhibition of VTA GABA neurons suppressed anxiety-related behavior in mice exposed to uFS.

These data show that VTA GABA neurons are an early substrate for stress-induced anxiety-related behavior in mice and suggest that approaches mitigating enhanced excitability of VTA GABA neurons may hold promise for the treatment of anxiety provoked by stress and trauma.

Assessing and responding to threats is vital in everyday life. Unfortunately, many mental illnesses involve impaired risk assessment, affecting patients, families, and society. The brain processes behind these behaviors are not well understood. We developed a transgenic mouse model (disrupted-in-schizophrenia 1 [DISC1]-N) with a disrupted avoidance response in risky settings. Our study utilized single-nucleus RNA sequencing and path-clamp coupling with real-time RT-PCR to uncover a previously undescribed group of glutamatergic neurons in the basolateral amygdala (BLA) marked by Wolfram syndrome 1 (WFS1) expression, whose activity is modulated by adjacent astrocytes. These neurons in DISC1-N mice exhibited diminished firing ability and impaired communication with the astrocytes. Remarkably, optogenetic activation of these astrocytes reinstated neuronal excitability via D-serine acting on BLAWFS1 neurons' NMDA receptors, leading to improved risk-assessment behavior in the DISC1-N mice. Our findings point to BLA astrocytes as a promising target for treating risk-assessment dysfunctions in mental disorders.

Anxiety is a complex phenomenon: Its eliciting stimuli and circumstances, component behaviors, and functional consequences are only slowly coming to be understood. Here, we examine defense systems from field studies; laboratory studies focusing on experimental analyses of behavior; and, the fear conditioning literature, with a focus on the role of uncertainty in promoting an anxiety pattern that involves high rates of stimulus generalization and resistance to extinction. Respectively, these different areas provide information on evolved elicitors of defense (field studies); outline a defense system focused on obtaining information about uncertain threat (ethoexperimental analyses); and, provide a simple, well-researched, easily measured paradigm for analysis of nonassociative stress-enhanced fear conditioning (the SEFL). Results suggest that all of these-each of which is responsive to uncertainty-play multiple and interactive roles in anxiety. Brain system findings for some relevant models are reviewed, with suggestions that further analyses of current models may be capable of providing a great deal of additional information about these complex interactions and their underlying biology.

Pavlovian fear conditioning research suggests that the interaction between the dorsal periaqueductal gray (dPAG) and basolateral amygdala (BLA) acts as a prediction error mechanism in the formation of associative fear memories. However, their roles in responding to naturalistic predatory threats, characterized by less explicit cues and the absence of reiterative trial-and-error learning events, remain unexplored. In this study, we conducted single-unit recordings in rats during an 'approach food-avoid predator' task, focusing on the responsiveness of dPAG and BLA neurons to a rapidly approaching robot predator. Optogenetic stimulation of the dPAG triggered fleeing behaviors and increased BLA activity in naive rats. Notably, BLA neurons activated by dPAG stimulation displayed immediate responses to the robot, demonstrating heightened synchronous activity compared to BLA neurons that did not respond to dPAG stimulation. Additionally, the use of anterograde and retrograde tracer injections into the dPAG and BLA, respectively, coupled with c-Fos activation in response to predatory threats, indicates that the midline thalamus may play an intermediary role in innate antipredatory defensive functioning.

The neural computations for looming detection are strikingly similar across species. In mammals, information about approaching threats is conveyed from the retina to the midbrain superior colliculus, where approach variables are computed to enable defensive behavior. Although neuroscientific theories posit that midbrain representations contribute to emotion through connectivity with distributed brain systems, it remains unknown whether a computational system for looming detection can predict both defensive behavior and phenomenal experience in humans. Here, we show that a shallow convolutional neural network based on the Drosophila visual system predicts defensive blinking to looming objects in infants and superior colliculus responses to optical expansion in adults. Further, the neural network's responses to naturalistic video clips predict self-reported emotion largely by way of subjective arousal. These findings illustrate how a simple neural network architecture optimized for a species-general task relevant for survival explains motor and experiential components of human emotion.

In the natural world, animals use vision for a wide variety of behaviors not reflected in most laboratory paradigms. Although mice have low-acuity vision, they use their vision for many natural behaviors, including predator avoidance, prey capture, and navigation. They also perform active sensing, moving their head and eyes to achieve behavioral goals and acquire visual information. These aspects of natural vision result in visual inputs and corresponding behavioral outputs that are outside the range of conventional vision studies but are essential aspects of visual function. Here, we review recent studies in mice that have tapped into natural behavior and active sensing to reveal the computational logic of neural circuits for vision.

Impaired long-term memory, a complication of traumatic stress including hemorrhage shock and resuscitation (HSR), has been reported to be associated with multiple neurodegenerations. The ventral tegmental area (VTA) participates in both learned appetitive and aversive behaviors. In addition to being prospective targets for the therapy of addiction, depression, and other stress-related diseases, VTA glutamatergic neurons are becoming more widely acknowledged as powerful regulators of reward and aversion. This study revealed that HSR exposure induces memory impairments and decreases the activation in glutamatergic neurons, and decreased β power in the VTA. We also found that optogenetic activation of glutamatergic neurons in the VTA mitigated HSR-induced memory impairments, and restored β power. Moreover, hydrogen sulfide (H2S), a gasotransmitter with pleiotropic roles, has neuroprotective functions at physiological concentrations. In vivo, H2S administration improved HSR-induced memory deficits, elevated c-fos-positive vesicular glutamate transporters (Vglut2) neurons, increased β power, and restored the balance of γ-aminobutyric acid (GABA) and glutamate in the VTA. This work suggests that glutamatergic neuron stimulation via optogenetic assay and exogenous H2S may be useful therapeutic approaches for improving memory deficits following HSR.

The superior colliculus (SC) is a prominent and conserved visual center in all vertebrates. In mice, the most superficial lamina of the SC is enriched with neurons that are selective for the moving direction of visual stimuli. Here, we study how these direction selective neurons respond to complex motion patterns known as plaids, using two-photon calcium imaging in awake male and female mice. The plaid pattern consists of two superimposed sinusoidal gratings moving in different directions, giving an apparent pattern direction that lies between the directions of the two component gratings. Most direction selective neurons in the mouse SC respond robustly to the plaids and show a high selectivity for the moving direction of the plaid pattern but not of its components. Pattern motion selectivity is seen in both excitatory and inhibitory SC neurons and is especially prevalent in response to plaids with large cross angles between the two component gratings. However, retinal inputs to the SC are ambiguous in their selectivity to pattern versus component motion. Modeling suggests that pattern motion selectivity in the SC can arise from a nonlinear transformation of converging retinal inputs. In contrast, the prevalence of pattern motion selective neurons is not seen in the primary visual cortex (V1). These results demonstrate an interesting difference between the SC and V1 in motion processing and reveal the SC as an important site for encoding pattern motion.

Escape is one of the most essential behaviors for an animal's survival because it could be a matter of life and death. Much of our current understanding of the neural mechanisms underlying escape is derived from the looming paradigm, which mimics a diving aerial predator. Yet, the idea of the looming paradigm does not account for all types of threats like lions hunting antelopes or cats stalking mice. Escape responses to such terrestrial threats may require different strategies and neural mechanisms.

Here, we developed a real-time interactive platform to study escape behavior to terrestrial threats in mice. A closed-loop controlled robot was magnetically pulled to mimic a terrestrial threat that chases a mouse. By using strong magnets and high-precision servo motors, the robot is capable of moving precisely with a high spatial-temporal resolution. Different algorithms can be used to achieve single approach or persistent approach.

Animal experiments showed that mice exhibited consistent escape behavior when exposed to an approaching robotic predator. When presented with a persistently approaching predator, the mice were able to rapidly adapt their behavior, as evidenced by a decrease in startle responses and changes in movement patterns.

In comparison to existing methods for studying escape behavior, such as the looming paradigm, this approach is more suitable for investigating animal behavior in response to sustained threats.

In conclusion, we have developed a flexible platform to study escape behavior to terrestrial threats in mice.

Immune activation is one of the most common complications during pregnancy, predominantly evoked by viral infections. Nevertheless, how immune activation affects mother-offspring relationships postpartum remains unknown. Here, by using the polyinosinic-polycytidylic acid (Poly I:C) model of gestational infection we show that viral-like immune activation at mid-gestation persistently changes hypothalamic neurocircuit parameters in mouse dams and, consequently, is adverse to parenting behavior. Poly I:C-exposed dams favor non-pup-directed exploratory behavior at the expense of pup retrieval. These behavioral deficits are underlain by dendrite pruning and lesser immediate early gene activation in Galanin (Gal)+ neurons with dam-specific transcriptional signatures that reside in the medial preoptic area (mPOA). Reduced activation of an exclusively inhibitory contingent of these distal-projecting Gal+ neurons allows for increased feed-forward inhibition onto putative dopaminergic neurons in the ventral tegmental area (VTA) in Poly I:C-exposed dams. Notably, destabilized VTA output specifically accompanies post-pup retrieval epochs. We suggest that gestational immunogenic insults bias both threat processing and reward perception, manifesting as disfavored infant caregiving.

The nucleus of Darkschewitsch (ND), mainly composed of GABAergic neurons, is widely recognized as a component of the eye-movement controlling system. However, the functional contribution of ND GABAergic neurons (NDGABA) in animal behavior is largely unknown. Here, we show that NDGABA neurons were selectively activated by different types of fear stimuli, such as predator odor and foot shock. Optogenetic and chemogenetic manipulations revealed that NDGABA neurons mediate freezing behavior. Moreover, using circuit-based optogenetic and neuroanatomical tracing methods, we identified an excitatory pathway from the lateral periaqueductal gray (lPAG) to the ND that induces freezing by exciting ND inhibitory outputs to the motor-related gigantocellular reticular nucleus, ventral part (GiV). Together, these findings indicate the NDGABA population as a novel hub for controlling defensive response by relaying fearful information from the lPAG to GiV, a mechanism critical for understanding how the freezing behavior is encoded in the mammalian brain.

The midbrain dopamine system is a sophisticated hub that integrates diverse inputs to control multiple physiological functions, including locomotion, motivation, cognition, reward, as well as maternal and reproductive behaviors. Dopamine is a neurotransmitter that binds to G-protein-coupled receptors. Dopamine also works together with other neurotransmitters and various neuropeptides to maintain the balance of synaptic functions. The dysfunction of the dopamine system leads to several conditions, including Parkinson's disease, Huntington's disease, major depression, schizophrenia, and drug addiction. The ventral tegmental area (VTA) has been identified as an important relay nucleus that modulates homeostatic plasticity in the midbrain dopamine system. Due to the complexity of synaptic transmissions and input-output connections in the VTA, the structure and function of this crucial brain region are still not fully understood. In this review article, we mainly focus on the cell types, neurotransmitters, neuropeptides, ion channels, receptors, and neural circuits of the VTA dopamine system, with the hope of obtaining new insight into the formation and function of this vital brain region.

Midbrain dopamine neurons are thought to signal reward prediction errors (RPEs), but the mechanisms underlying RPE computation, particularly the contributions of different neurotransmitters, remain poorly understood. Here, we used a genetically encoded glutamate sensor to examine the pattern of glutamate inputs to dopamine neurons in mice. We found that glutamate inputs exhibit virtually all of the characteristics of RPE rather than conveying a specific component of RPE computation, such as reward or expectation. Notably, whereas glutamate inputs were transiently inhibited by reward omission, they were excited by aversive stimuli. Opioid analgesics altered dopamine negative responses to aversive stimuli into more positive responses, whereas excitatory responses of glutamate inputs remained unchanged. Our findings uncover previously unknown synaptic mechanisms underlying RPE computations; dopamine responses are shaped by both synergistic and competitive interactions between glutamatergic and GABAergic inputs to dopamine neurons depending on valences, with competitive interactions playing a role in responses to aversive stimuli.