Behavioral Neuroscience publications

Affective and consumption circuits in the brain are intertwined, with changes in each domain often affecting the other. Therapeutic interventions that reduce consumption, thereby facilitating weight loss, have tended to increase anxiety and depression. Obesity is a major risk factor for poor health; thus, it is important to understand the circuits and signals that regulate consummatory and affective behavior. Neurons expressing Urocortin-1 (Ucn) in the Edinger-Westphal (EW) nucleus have been hypothesized to play an important role in regulating both consummatory and affective behavioral domains and responses to stress. We generated UcnCre mice to allow measurement of Ucn neuron calcium activity and to directly activate these neurons during consummatory behaviors and repeated restraint stress. Our findings provide evidence for Ucn neuron regulation of consummatory behaviors and some affective behaviors.

Post-traumatic stress disorder (PTSD) develops in a sub-population of people exposed to trauma and is highly comorbid with opioid use disorder (OUD). The neurobiology of comorbid PTSD+OUD, especially with respect to sex differences, is poorly understood. Here we investigated the sex-specific effects of predator scent stress on intravenous (IV) oxycodone self-administration (SA), cue-primed reinstatement, and pre- and post-stress corticosterone (CORT) concentrations. Upon detecting effects of stress on oxycodone IVSA, the nucleus accumbens (NA) dopamine response to oxycodone was assessed. Male and female rats received a single 10-minute exposure to the predator scent TMT or the control condition. One week later, rats were tested for anxiety-like behavior on the elevated plus maze and underwent oxycodone IVSA, instrumental extinction, and a cue-primed reinstatement test. In a separate cohort of only female rats, the NA core dopamine response to IV oxycodone (0, 0.25, 0.5 mg/kg) was assessed using fiber photometry. TMT increased anxiety-like behavior one week later in male and female rats. Baseline CORT was negatively correlated with anxiety-like behavior in males. TMT exposure reduced oxycodone intake exclusively in females, with no effects on instrumental extinction or cue-primed reinstatement in either sex. Female rats demonstrated a dose-dependent increase in NA core dopamine signal following oxycodone administration that was blunted by a history of TMT exposure. These results indicate that TMT exposure diminishes the NA core dopamine response to oxycodone in females, reducing oxycodone IVSA. These results are consistent with stress-induced reward insensitivity that has been observed following stress in both rodents and humans.

Animals continuously adapt their behavior to balance survival and fulfilling essential needs. This balancing act involves prioritization of safety over the pursuit of other needs. However, the specific deep brain circuits that regulate safety-seeking behaviors in conjunction with motor circuits remain poorly understood. Here, we identify a class of glutamatergic neurons in the mouse lateral hypothalamic area (LHA) that target the midbrain locomotor-promoting pedunculopontine nucleus (PPN). Following activation, this LHA-PPN pathway orchestrates context-dependent locomotion, prioritizing safety-directed movement over other essential needs such as foraging or social contact. Remarkably, the neuronal activity of this circuit correlates directly with safety-seeking behavior. The circuit may respond to both intrinsic and extrinsic cues, having a pivotal role in ensuring survival. Our findings uncover a circuit motif within the lateral hypothalamus that, when recruited, prioritizes critical needs through the recruitment of an appropriate motor action.

Many animal training paradigms rely on head-fixation. Head-fixation training is typically laborious and can benefit from automation to relieve the workload and reduce the variability in the training outcome. Several groups have reported successful implementations of such systems, but throughput varied greatly across groups. In addition, most studies relied on brief periods of head-fixation sessions (≤ 1 minute) to reduce the potential stress on the animal. Here, we report the design of a new system that could achieve head-fixation sessions on the order of minutes with a high participation rate from the animal (100%). Throughout the training period, each mouse performed a total of close to 40 minutes of head-fixation training on average each day and learned common psychoacoustic tasks, i.e., tone detection and tone discrimination. Our system can achieve highly efficient training with minimum idling time, allowing combinations with high-end neural recording equipment to achieve maximum training and data collection efficiency.

For patients with severe and profound hearing loss, cochlear implant (CI), a common and effective modality for restoring hearing, directly stimulates spiral ganglion neurons (SGNs) to generate electrical activity and form auditory perception. However, the postoperative outcome of CI is significantly influenced by the number of surviving SGNs, ​​which is a key focus of preoperative evaluation​​. Existing audiologic function and radiographic tests cannot directly demonstrate the integrity of inner ear primary neurons. In this study, ​​we developed and validated​​ a radionuclide‐labeled anti‐vesicular glutamate transporter 1 (anti‐VGLUT1) antibody‐drug and achieved animal‐level in vivo imaging of cochlear SGNs using nuclear imaging. By screening the public single‐cell sequencing database, it is found that VGLUT1 can serve as a representative cell membrane marker for SGN in the cochlea. The potential of anti‐VGLUT1 conjugated to the long half‐life 177 Lu as a molecular probe to detect the relative number of SGNs in SGN‐injured mouse and pig models is explored. The study provides a novel method for assessing cochlear nerve integrity in vivo by visualizing target antigen expression levels through nuclear imaging. This approach is promising to help CI candidates with preoperative inner ear SGN integrity assessment, contributing to clinical decision‐making.

The posterior medial (POm) thalamus is heavily interconnected with sensory and motor circuitry and is likely involved in behavioral modulation and sensorimotor integration. POm provides axonal projections to the dorsal striatum, a hotspot of sensorimotor processing, yet the role of POm-striatal projections has remained undetermined. Using optogenetics with mouse brain slice electrophysiology, we found that POm provides robust synaptic input to direct and indirect pathway striatal spiny projection neurons (D1- and D2-SPNs, respectively) and parvalbumin-expressing fast spiking interneurons (PVs). During the performance of a whisker-based tactile discrimination task in head-restrained mice, POm-striatal projections displayed learning-related activation correlating with anticipatory, but not reward-related, pupil dilation. Inhibition of POm-striatal axons across learning caused slower reaction times and an increase in the number of training sessions for expert performance. Our data indicate that POm-striatal inputs provide a behaviorally relevant arousal-related signal, which may prime striatal circuitry for efficient integration of subsequent choice-related inputs.

Tinnitus is a prevalent and distressing medical symptom, and no effective pharmacological treatment currently exists. Despite significant advances, tinnitus remains a scientific enigma. To explore the molecular underpinnings of tinnitus, we developed a noise-induced tinnitus model in mice and utilized metabolomics to identify key differences in metabolic pathways. Our results revealed that oxidative stress-related pathways, including glutathione (GSH) metabolism, were significantly enriched in the auditory cortex of mice exhibiting tinnitus-like behavior. To further explore the role of oxidative stress, we examined the involvement of nuclear factor erythroid 2-related factor 2 (Nrf2) in tinnitus by conducting experiments in Nrf2 knockout (Nrf2-KO) mice. While Nrf2-deficient mice did not develop spontaneous tinnitus or hearing loss, they displayed increased susceptibility to prolonged tinnitus-like behavior after noise exposure. This was accompanied by heightened microglial activation, neuroinflammation, and significant alterations in gut microbiota composition, including greater diversity and dysbiosis. Our findings highlight a novel mechanism underlying tinnitus, emphasizing the role of oxidative stress in the auditory cortex and its connection to noise-induced tinnitus. The deficiency of Nrf2 in mice increases their susceptibility to tinnitus, suggesting that Nrf2 may serve as a promising therapeutic target for preventing noise-induced tinnitus.

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.

Transcranial focused ultrasound stimulation (tFUS) is a promising neuromodulation technique capable of noninvasively modulating focal neuronal activities and neural circuits in both animals and humans. The cell-type selectivity of tFUS within targeted areas such as the somatosensory cortex (S1) during sonication has been shown to be parameter related. However, it remains unclear how tFUS affects neural circuits by changing the correlation between neurons and how to optimize the tFUS parameters to modulate neural pathways. In this study, multisite intracranial recordings are used in anesthetized male rats to quantify the neuronal responses to tFUS stimulation recorded from S1 and posterior medial thalamic nucleus (POm) of cortico-thalamo-cortical (CTC) pathway. Different tFUS parameters including ranges of pulse repetition frequencies (PRFs) and duty cycles (DCs) are tested. We find that when targeting at S1, only regular-spiking units (RSUs) respond to specific tFUS parameters during sonication (DC, 6−60%; PRF, 1,500, 3,000 and 4,500 Hz), and RSUs from the POm exhibit a synchronized response. The changes of directional correlation between S1 RSUs and POm RSUs indicate the activation of feedback modulation. Delayed responses and correlation changes were further observed at ∼200 ms postsonication from the neurons in S1 and POm, indicating feedforward modulation. Our results reveal that tFUS can modulate the feedback and feedforward CTC pathways by selectively activating cortical RSUs and adjusting the tFUS parameters, particularly the PRF, to maximize cortical RSU activity could enhance the modulation of the CTC pathway.

Phenylketonuria (PKU), an inborn error of phenylalanine (Phe) metabolism, is a common cause of intellectual disability. However, the mechanisms by which elevated Phe levels cause cognitive impairment remain unclear. Here, we show that submillimolar Phe perturbs synaptic plasticity through the hyperactivation of GluN2B-containing NMDARs. Pah Enu2 PKU model mice exhibited submillimolar and supramillimolar concentrations of Phe in the cerebrospinal fluid (CSF) and serum, respectively. l-Phe produced concentration-dependent bidirectional effects on NMDA-induced currents, without affecting synaptic NMDA receptors (NMDARs) in hippocampal CA1 neurons. l-Phe-induced hyperactivation of extrasynaptic GluN2B resulted in activity-dependent downregulation of AMPA receptors during burst or sustained synaptic activity. Administration of l-Phe in mice decreased neural activity and impaired memory, which were blocked by pretreatment with GluN2B inhibitors. Furthermore, pharmacological and virus-mediated suppression of GluN2B reversed the impaired learning in Pah Enu2 mice. Collectively, these results suggest the concentration of Phe in the CSF of patients with PKU perturbs extrasynaptic NMDARs and synaptic plasticity and that suppression of GluN2B may have the potential to improve cognitive function in patients with PKU.

Flexible behaviour requires decision-making that integrates both perceptual and mnemonic-related information. While the dorsal premotor cortex (PMd) is known to support decision-making based on perceptual computations, its contributions to decisions based on mnemonic information for motor planning are underexplored. Here, investigating local field potential (LFP) oscillations in PMd of monkeys performing a transitive inference task required the formation and retrieval of mnemonic representations of an arbitrarily defined rank order among perceptual items. Our results highlight that a dynamic interplay between lower frequencies (Theta, Alpha, Beta) and high-Gamma oscillatory activity of LFP reflects a mechanism for accessing and manipulating memory-related information underlying decision-making. These findings provide evidence that the PMd plays a role in multiplexing both perceptual and mnemonic information, extending its competence beyond the association of perceptual input with motor decisions.

The hippocampus1-6, as well as dopamine circuits7-9, coordinates decision-making in anxiety-eliciting situations. Yet, little is known about how dopamine modulates hippocampal representations of emotionally salient stimuli to inform appropriate resolution of approach versus avoidance conflicts. Here we studied dopaminoceptive neurons in the male mouse ventral hippocampus (vHipp), molecularly distinguished by their expression of dopamine D1 or D2 receptors. We show that these neurons are transcriptionally distinct and topographically organized across vHipp subfields and cell types. In the ventral subiculum where they are enriched, both D1 and D2 neurons are recruited during anxiogenic exploration, yet with distinct profiles related to investigation and behavioural selection. In turn, they mediate opposite approach-avoidance responses, and are differentially modulated by dopaminergic transmission in that region. Together, these results suggest that vHipp dopamine dynamics gate exploratory behaviours under contextual uncertainty, implicating dopaminoception in the complex computation engaged in the vHipp to govern emotional states.

Conditioned suppression is a useful paradigm for measuring learned avoidance. In most conditioned suppression studies, forward conditioning is used where a cue predicts an aversive stimulus. However, backward conditioning, in which an aversive stimulus predicts a cue, provides unique insights into learned avoidance due to its influence on both conditioned excitation and inhibition. We trained mice to consume sucrose in context A, associated an aversive stimulus in context B to few or many forward or backwards paired cues (CS + ), and then tested for conditioned suppression in context A in response to the CS + . We found that few or many forward CS + and few backward CS + produced conditioned suppression, but many backwards cues did not. Administration of diazepam, a positive allosteric modulator of the GABAA receptor, prevented conditioned suppression to the backward CS + but not to the forward CS + . Furthermore, freezing behavior was observed in response to the forward CS + but not the backward CS+, and diazepam had no effect on freezing or locomotion. We next examined BNST GABA neurons for potential sensitivity to backwards cues and conditioned suppression. VGaT BNST signaling increased in response to sucrose licks during the backward CS + but not to licks outside the CS + and not to the backward CS + onset or offset. Using designer receptors, we found that BNST VGaT neuron activation, but not its inhibition, prevented backward conditioned suppression expression. We conclude that backward conditioned suppression is dependent on both positive allosteric modulation of GABA on GABAA receptors by diazepam and BNST GABA neurons.

Avoidance learning-learning to avoid bad outcomes-is an essential survival behavior. Dopamine signals are widely observed in response to aversive stimuli, indicating they could play a role in learning about how to avoid these stimuli.1,2,3,4,5 However, it is unclear what computations dopamine signals perform to support avoidance learning. Furthermore, substantial heterogeneity in dopamine responses to aversive stimuli has been observed across nucleus accumbens (NAc) subregions.3,6,7,8 To understand how heterogeneous dopamine responses to aversive stimuli contribute to avoidance learning, we recorded NAc core (Core) and NAc ventromedial shell (vmShell) dopamine during a task in which mice could avoid a footshock punishment by moving to the opposite side of a 2-chamber apparatus during a 5-s warning cue. Both signals evolved substantially-but differently-with learning. We found that Core and vmShell dopamine signals responded oppositely to shocks at the beginning of training and oppositely to warning cues as cue-shock associations developed in mid-training. Core dopamine responses strengthen with learning and are especially evident during expert performance. vmShell dopamine responses to cues and shocks were present during early learning but were not sustained during expert performance. Our data support a model in which Core dopamine encodes prediction errors that guide the consolidation of avoidance learning, while vmShell dopamine guides initial cue-shock associations by signaling aversive salience.

The dopaminergic system is crucial for affect regulation. Melanocortin 4 receptors (MC4R) in the ventral striatum have been shown to be necessary for establishing aversive states. Here, we functionally characterize MC4R-expressing striatal neurons in mice. MC4Rs were enriched in atypical dopamine receptor 1 (D1) neurons in the lateral stripe of the striatum (LSS), an understudied area in the ventrolateral striatum. Fiber photometry recordings showed that MC4R neuron activity and local dopamine release in the LSS increased in response to both rewarding and aversive stimuli. Moreover, MC4R neuronal activity and glutamate release in the LSS correlated with body movement. Optogenetic activation of MC4R-LSS neurons was rewarding in a real-time place preference test and a self-stimulation paradigm, increased locomotor activity, and induced striatal dopamine release. Collectively, our findings suggest that MC4R-LSS neurons are activated by stimuli of both rewarding and aversive character and that they induce positive affect, dopamine release and locomotion.

Although control of movement involves many cortical association areas, bidirectional brain-machine interfaces (BMIs) typically decode movement intent from the motor cortex and deliver feedback information to the primary somatosensory cortex (S1). Compared to the S1, the parietal and premotor areas encode more complex information about object properties, hand pre-shaping, and reach trajectories. BMIs therefore might deliver richer information to those cortical association areas than to primary areas. Here, we investigated whether instructions for a center-out task could be delivered via intracortical microstimulation (ICMS) in the anterior intraparietal area (AIP), dorsal posterior parietal cortex (dPPC), or dorsal premotor cortex (PMd) as well as the ventral premotor cortex (PMv) and S1. Two monkeys successfully learned to use AIP, PMv, or S1-ICMS instructions, but neither learned to use dPPC- or PMd-ICMS instructions. The AIP, PMv, and S1 may thus be effective cortical territory for delivering information to the brain, whereas the dPPC or PMd may be comparatively ineffective.

Foraging theory predicts animal behavior in many contexts. In patch-based foraging behaviors, the marginal value theorem (MVT) gives the optimal strategy for deterministic environments whose parameters are fully known to the forager. In natural settings, environmental parameters exhibit variability and are only partially known to the animal based on its experience, creating uncertainty. Models of uncertainty in foraging are well established. However, natural environments also exhibit unpredicted changes in their statistics. As a result, animals must ascertain whether the currently observed quality of the environment is consistent with their internal models, or whether something has changed, creating meta-uncertainty. Behavioral strategies for optimizing foraging behavior under meta-uncertainty, and their neural underpinnings, are largely unknown. Here, we developed a novel behavioral task and computational framework for studying patch-leaving decisions in head-fixed and freely moving mice in conditions of meta-uncertainty. We stochastically varied between-patch travel time, as well as within-patch reward depletion rate. We find that, when uncertainty is minimal, mice adopt patch residence times in a manner consistent with the MVT and not explainable by simple ethologically motivated heuristic strategies. However, behavior in highly variable environments was best explained by modeling both first- and second-order uncertainty in environmental parameters, wherein local variability and global statistics are captured by a Bayesian estimator and dynamic prior, respectively. Thus, mice forage under meta-uncertainty by employing a hierarchical Bayesian strategy, which is essential for efficiently foraging in volatile environments. The results provide a foundation for understanding the neural basis of decision-making that exhibits naturalistic meta-uncertainty.

The ability to evaluate valence of a social agent based on social experience is essential for an animal's survival in its social group1. Although hippocampal circuits have been implicated in distinguishing novel and familiar conspecifics2-7, it remains unclear how social valence is constructed on the basis of social history and what mechanisms underlie the heightened valence versatility in dynamic relationships. Here we demonstrate that the ventral (v)CA1 integrates serotonin (5-HT) inputs from the dorsal raphe and neurotensin inputs from the paraventricular nucleus of the thalamus (PVT) to determine positive or negative valence of conspecific representations. Specifically, during an appetitive social interaction 5-HT is released into the vCA1 and disinhibits pyramidal neurons through 5-HT1B receptors, whereas neurotensin is released during an aversive social interaction and potentiates vCA1 neurons directly through NTR1s. Optogenetic silencing of dorsal raphe 5-HT and PVT neurotensin inputs into the vCA1 impairs positive and negative social valence, respectively, and excitation flexibly switches valence assignment. These results show how aversive and rewarding social experiences are linked to conspecific identity through converging dorsal raphe 5-HT and PVT neurotensin signals in the vCA1 that instruct opposing valence, and represent a synaptic switch for flexible social valence computation.

Social novelty preference is an important aspect of social interaction for evaluating new threats and opportunities for survival, but the underlying neuronal mechanism remains unclear. Here, we identify a molecularly defined medial prefrontal cortex (mPFC) excitatory neuron subtype, located in layer 5 expressing Il1rapl2 , which is highly associated with social deficit disorders in genome-wide association studies and might be responsible for regulating social novelty preference. Using an Il1rapl2 -Cre mouse line, we show that chemogenetic activation of the mPFC Il1rapl2 -expressing neurons impairs social novelty preference but with little effect on sociability. In addition, fiber photometry recording indicates that this neuron subtype is inhibited when mice interact with novel but not with familiar mice. Furthermore, viral tracing and terminal manipulation reveal that basolateral amygdala (BLA)–projecting Il1rapl2 + neurons mediate the social novelty preference. Thus, our study uncovers a molecularly defined mPFC-BLA circuit that specifically regulates social novelty preference, highlighting that specific neuron subtypes and circuits could modulate distinct aspects of social behaviors.

The hippocampus (HPC) supports spatial working memory (SWM) through its interactions with the prefrontal cortex (PFC). However, it is not clear whether and how the dorsal (dHPC) and ventral (vHPC) poles of the HPC make distinct contributions to SWM and whether they differentially influence the PFC. To address this question, we optogenetically silenced the dHPC or the vHPC while simultaneously recording from the PFC of mice performing a SWM task. We found that whereas both HPC subregions were necessary during the encoding phase of the task, only the dHPC was necessary during the choice phase. Unexpectedly, silencing of either subregion did not affect PFC neurons’ ability to represent the animal’s position, but did alter how it was represented. In contrast, only silencing of the vHPC affected their coding of spatial goals. These results thus reveal distinct contributions of the dorsal and ventral HPC poles to SWM and the coding of behaviorally relevant spatial information by PFC neurons.