Unfolding the direct connectivity of the occipital cortex with the hypothalamic, septal and BNST nuclei of the human brain.

The hypothalamus plays essential roles in the human brain by regulating feeding, fear, aggression, reproductive behaviors, and autonomic activities. The septal nuclei and the bed nucleus of stria terminalis (BNST) are also known to be involved in control of autonomic, motivational, learning, emotional and associative processes in the human brain. Multiple animal dissection studies have revealed direct connectivity between central limbic gray matter nuclei and occipital cortex, particularly from the hypothalamic, septal and BNST nuclei. However, the detailed anatomy of this connectivity in the human brain has yet to be determined. The primary objective of this study was to explore the utility of high spatial and high angular resolution diffusion weighted tractography techniques for mapping the connectivity pathways between the occipital cortex and central limbic gray matter nuclei in the human brain. We studied 30 healthy adult human brains, delineated, and reconstructed the trajectory of the occipito-hypothalamic/septal/BNST for the first time in the human brain.

Sex and age differences in the distribution of estrogen receptors in mice.

Estrogen receptors (ERα and ERß) are crucial for the regulation of socio-sexual behaviors and the organization of sex-specific neural networks in the developing brain. However, how the distribution patterns of ERα and ERß change throughout life is unclear. Using genetically modified ERß-RFPtg mice, we investigated the distribution of ERα, ERß, and their colocalization in the ventromedial nucleus of the hypothalamus (VMH), anteroventral periventricular nucleus (AVPV), and bed nucleus of stria terminalis (BNST) from postnatal days (PD) 0 to 56. ERα expression was higher in females that showed an increase after PD14 in all brain regions, whereas ERß-RFP expression pattern was markedly different among the regions. In the VMH, ERß-RFP was highly expressed on PD0 and PD7 but decreased drastically to very low expression afterward in both sexes. In contrast, ERß-RFP expression was higher in females compared to males in the AVPV but lower in the BNST throughout life especially late- and post-pubertal periods. Our results demonstrating that ERα and ERß-RFP expression changed in a sex-, age- and region-specific manner contribute to further clarification of the mechanisms underlying estrogen-dependent organization of the brain in both sexes.

The altered sensitivity of acute stress induced anxiety-related behaviors by modulating insular cortex-paraventricular thalamus-bed nucleus of the stria terminalis neural circuit.

The dysregulation of neuronal networks contributes to the etiology of psychiatric diseases, including anxiety. However, the neural circuits underlying anxiety symptoms remain unidentified. We observed acute restraint stress activating excitatory neurons in the paraventricular thalamus (PVT). Activation of PVT neurons caused anxious behaviors, whereas suppression of PVT neuronal activity induced an anxiolytic effect, achieved by using a chemogenetic method. Moreover, we found that the PVT neurons showed plentiful neuronal projections to the bed nucleus of the stria terminalis (BNST). Activation of PVT-BNST neural projections increased the susceptibility of stress-induced anxiety-related behaviors, and inhibition of this neural circuit produced anxiolysis. The insular cortex (IC) is an important upstream region projecting to PVT. Activation of IC-PVT neuronal projections enhanced susceptibility to stress induced anxious behaviors. Inhibiting this neural circuit suppressed anxious behaviors. Moreover, anterograde monosynaptic tracing results showed that the IC exerts strong neuronal projections to PVT, forming synaptic connections with its neurons, and these neurons throw extensive neuronal fibers to form synapse with BNST neurons. Finally, our results showed that ablation of neurons in PVT receiving monosynaptic input from IC attenuated the anxiety-related phenotypes induced by activating IC neurons. Lesions of the neurons in BNST synaptic origination from PVT blocked the anxiety-related phenotypes induced by activating PVT neurons. Our findings indicate that the PVT is a crucial anxiety-regulating nucleus, and the IC-PVT-BNST neural projection is an essential pathway affecting anxiety morbidity and treatment.

The PACAP Paradox: Dynamic and Surprisingly Pleiotropic Actions in the Central Regulation of Energy Homeostasis.

Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP), a pleiotropic neuropeptide, is widely distributed throughout the body. The abundance of PACAP expression in the central and peripheral nervous systems, and years of accompanying experimental evidence, indicates that PACAP plays crucial roles in diverse biological processes ranging from autonomic regulation to neuroprotection. In addition, PACAP is also abundantly expressed in the hypothalamic areas like the ventromedial and arcuate nuclei (VMN and ARC, respectively), as well as other brain regions such as the nucleus accumbens (NAc), bed nucleus of stria terminalis (BNST), and ventral tegmental area (VTA) - suggesting that PACAP is capable of regulating energy homeostasis via both the homeostatic and hedonic energy balance circuitries. The evidence gathered over the years has increased our appreciation for its function in controlling energy balance. Therefore, this review aims to further probe how the pleiotropic actions of PACAP in regulating energy homeostasis is influenced by sex and dynamic changes in energy status. We start with a general overview of energy homeostasis, and then introduce the integral components of the homeostatic and hedonic energy balance circuitries. Next, we discuss sex differences inherent to the regulation of energy homeostasis via these two circuitries, as well as the activational effects of sex steroid hormones that bring about these intrinsic disparities between males and females. Finally, we explore the multifaceted role of PACAP in regulating homeostatic and hedonic feeding through its actions in regions like the NAc, BNST, and in particular the ARC, VMN and VTA that occur in sex- and energy status-dependent ways.

Macroscale connections of the mouse lateral preoptic area and anterior lateral hypothalamic area.

The macroscale neuronal connections of the lateral preoptic area (LPO) and the caudally adjacent lateral hypothalamic area anterior region (LHAa) were investigated in mice by anterograde and retrograde axonal tracing. Both hypothalamic regions are highly and diversely connected, with connections to >200 gray matter regions spanning the forebrain, midbrain, and rhombicbrain. Intrahypothalamic connections predominate, followed by connections with the cerebral cortex and cerebral nuclei. A similar overall pattern of LPO and LHAa connections contrasts with substantial differences between their input and output connections. Strongest connections include outputs to the lateral habenula, medial septal and diagonal band nuclei, and inputs from rostral and caudal lateral septal nuclei; however, numerous additional robust connections were also observed. The results are discussed in relation to a current model for the mammalian forebrain network that associates LPO and LHAa with a range of functional roles, including reward prediction, innate survival behaviors (including integrated somatomotor and physiological control), and affect. The present data suggest a broad and intricate role for LPO and LHAa in behavioral control, similar in that regard to previously investigated LHA regions, contributing to the finely tuned sensory-motor integration that is necessary for behavioral guidance supporting survival and reproduction.

Deep brain stimulation in the bed nucleus of the stria terminalis: A symptom provocation study in patients with obsessive-compulsive disorder.

BACKGROUND: Deep brain stimulation (DBS) is an emerging therapy for treatment-resistant obsessive-compulsive disorder (OCD), and several targets for electrode implantation and contact selection have been proposed, including the bed nucleus of the stria terminalis (BST). Selecting the active electrode contacts (patients typically have four to choose from in each hemisphere), and thus the main locus of stimulation, can be a taxing process. Here, we investigated whether contact selection based purely on their neuroanatomical position in the BST is a worthwhile approach. For the first time, we also compared the effects of uni- versus bilateral BST stimulation. METHODS: Nine OCD patients currently receiving DBS participated in a double-blind, randomized symptom provocation study to compare no versus BST stimulation. Primary outcomes were anxiety and mood ratings in response to disorder-relevant trigger images, as well as ratings of obsessions, compulsions, tendency to avoid and overall wellbeing. Furthermore, we asked whether patients preferred the electrode contacts in the BST over their regular stimulation contacts as a new treatment setting after the end of the task. RESULTS: We found no statistically significant group differences between the four conditions (no, left, right and bilateral BST stimulation). Exploratory analyses, as well as follow-up data, did indicate that (bilateral) bipolar stimulation in the BST was beneficial for some patients, particularly for those who had achieved unsatisfactory effects through the typical contact selection procedure. CONCLUSIONS: Despite its limitations, this study suggests that selection of stimulation contacts in the BST is a viable option for DBS in treatment-resistant OCD patients.

A Neural Circuit from the Paraventricular Thalamus to the Bed Nucleus of the Stria Terminalis for the Regulation of States of Consciousness during Sevoflurane Anesthesia in Mice.

BACKGROUND: The neural circuitry underlying sevoflurane-induced modulation of consciousness is poorly understood. This study hypothesized that the paraventricular thalamus bed nucleus of the stria terminalis pathway plays an important role in regulating states of consciousness during sevoflurane anesthesia. METHODS: Rabies virus-based transsynaptic tracing techniques were employed to reveal the neural pathway from the paraventricular thalamus to the bed nucleus of the stria terminalis. This study investigated the role of this pathway in sevoflurane anesthesia induction, maintenance, and emergence using chemogenetic and optogenetic methods combined with cortical electroencephalogram recordings. Both male and female mice were used in this study. RESULTS: Both γ-aminobutyric acid-mediated and glutamatergic neurons in the bed nucleus of the stria terminalis receive paraventricular thalamus glutamatergic projections. Chemogenetic inhibition of paraventricular thalamus glutamatergic neurons prolonged the sevoflurane anesthesia emergence time (mean ± SD, hM4D-clozapine N-oxide vs. mCherry-clozapine N-oxide, 281 ± 88 vs. 172 ± 48 s, P < 0.001, n = 24) and decreased the induction time (101 ± 32 vs. 136 ± 34 s, P = 0.002, n = 24), as well as the EC5 0 for the loss or recovery of the righting reflex under sevoflurane anesthesia (mean [95% CI] for the concentration at which 50% of the mice lost their righting reflex, 1.16 [1.12 to 1.20] vs. 1.49 [1.46 to 1.53] vol%, P < 0.001, n = 20; and for the concentration at which 50% of the mice recovered their righting reflex, 0.95 [0.86 to 1.03] vs. 1.34 [1.29 to 1.40] vol%, P < 0.001, n = 20). Similar results were observed during suppression of the paraventricular thalamus bed nucleus-stria terminalis pathway. Optogenetic activation of this pathway produced the opposite effects. Additionally, transient stimulation of this pathway efficiently induced behavioral arousal during continuous steady-state general anesthesia with sevoflurane and reduced the depth of anesthesia during sevoflurane-induced burst suppression. CONCLUSIONS: In mice, axonal projections from the paraventricular thalamic neurons to the bed nucleus of the stria terminalis contribute to regulating states of consciousness during sevoflurane anesthesia.

The paraventricular thalamus provides a polysynaptic brake on limbic CRF neurons to sex-dependently blunt binge alcohol drinking and avoidance behavior in mice.

Bed nucleus of the stria terminalis (BNST) neurons that synthesize corticotropin-releasing factor (CRF) drive binge alcohol drinking and anxiety. Here, we found that female C57BL/6J mice binge drink more than males and have greater basal BNSTCRF neuron excitability and synaptic excitation. We identified a dense VGLUT2 + synaptic input from the paraventricular thalamus (PVT) that releases glutamate directly onto BNSTCRF neurons but also engages a large BNST interneuron population to ultimately inhibit BNSTCRF neurons, and this polysynaptic PVTVGLUT2-BNSTCRF circuit is more robust in females than males. Chemogenetic inhibition of the PVTBNST projection promoted binge alcohol drinking only in female mice, while activation reduced avoidance behavior in both sexes. Lastly, repeated binge drinking produced a female-like phenotype in the male PVT-BNSTCRF excitatory synapse without altering the function of PVTBNST neurons per se. Our data describe a complex, feedforward inhibitory PVTVGLUT2-BNSTCRF circuit that is sex-dependent in its function, behavioral roles, and alcohol-induced plasticity.

A metabolic function of the hippocampal sharp wave-ripple.

The hippocampus has previously been implicated in both cognitive and endocrine functions1-15. We simultaneously measured electrophysiological activity from the hippocampus and interstitial glucose concentrations in the body of freely behaving rats to identify an activity pattern that may link these disparate functions of the hippocampus. Here we report that clusters of sharp wave-ripples recorded from the hippocampus reliably predicted a decrease in peripheral glucose concentrations within about 10 min. This correlation was not dependent on circadian, ultradian or meal-triggered fluctuations, could be mimicked with optogenetically induced ripples in the hippocampus (but not in the parietal cortex) and was attenuated to chance levels by pharmacogenetically suppressing activity of the lateral septum, which is the major conduit between the hippocampus and the hypothalamus. Our findings demonstrate that a function of the sharp wave-ripple is to modulate peripheral glucose homeostasis, and offer a mechanism for the link between sleep disruption and blood glucose dysregulation in type 2 diabetes16-18.

Functional anatomy of the bed nucleus of the stria terminalis-hypothalamus neural circuitry: Implications for valence surveillance, addiction, feeding, and social behaviors.

The bed nucleus of the stria terminalis (BNST) is a medial basal forebrain structure that modulates the hypothalamo-pituitary-adrenal (HPA) axis. The heterogeneous subnuclei of the BNST integrate inputs from mood and reward-related areas and send direct inhibitory projections to the hypothalamus. The connections between the BNST and hypothalamus are conserved across species, promote activation of the HPA axis, and can increase avoidance of aversive environments, which is historically associated with anxiety behaviors. However, BNST-hypothalamus circuitry is also implicated in motivated behaviors, drug seeking, feeding, and sexual behavior. These complex and diverse roles, as well its sexual dimorphism, indicate that the BNST-hypothalamus circuitry is an essential component of the neural circuitry that may underlie various psychiatric diseases, ranging from anorexia to anxiety to addiction. The following review is a cross-species exploration of BNST-hypothalamus circuitry. First, we describe the BNST subnuclei, microcircuitry and complex reciprocal connections with the hypothalamus. We will then discuss the behavioral functions of BNST-hypothalamus circuitry, including valence surveillance, addiction, feeding, and social behavior. Finally, we will address sex differences in morphology and function of the BNST and hypothalamus.

Neural substrates of human fear generalization: A 7T-fMRI investigation.

Fear generalization - the tendency to interpret ambiguous stimuli as threatening due to perceptual similarity to a learned threat - is an adaptive process. Overgeneralization, however, is maladaptive and has been implicated in a number of anxiety disorders. Neuroimaging research has indicated several regions sensitive to effects of generalization, including regions involved in fear excitation (e.g., amygdala, insula) and inhibition (e.g., ventromedial prefrontal cortex). Research has suggested several other small brain regions may play an important role in this process (e.g., hippocampal subfields, bed nucleus of the stria terminalis [BNST], habenula), but, to date, these regions have not been examined during fear generalization due to limited spatial resolution of standard human neuroimaging. To this end, we utilized the high spatial resolution of 7T fMRI to characterize the neural circuits involved in threat discrimination and generalization. Additionally, we examined potential modulating effects of trait anxiety and intolerance of uncertainty on neural activation during threat generalization. In a sample of 31 healthy undergraduate students, significant positive generalization effects (i.e., greater activation for stimuli with increasing perceptual similarity to a learned threat cue) were observed in the visual cortex, thalamus, habenula and BNST, while negative generalization effects were observed in the dentate gyrus, CA1, and CA3. Associations with individual differences were underpowered, though preliminary findings suggested greater generalization in the insula and primary somatosensory cortex may be correlated with self-reported anxiety. Overall, findings largely support previous neuroimaging work on fear generalization and provide additional insight into the contributions of several previously unexplored brain regions.

Optimization of whole-brain rabies virus tracing technology for small cell populations.

The lateral hypothalamus (LH) is critically involved in the regulation of homeostatic energy balance. Some neurons in the LH express receptors for leptin (LepRb), a hormone known to increase energy expenditure and decrease energy intake. However, the neuroanatomical inputs to LepRb-expressing LH neurons remain unknown. We used rabies virus tracing technology to map these inputs, but encountered non-specific tracing. To optimize this technology for a minor cell population (LepRb is not ubiquitously expressed in LH), we used LepRb-Cre mice and assessed how different titers of the avian tumor virus receptor A (TVA) helper virus affected rabies tracing efficiency and specificity. We found that rabies expression is dependent on TVA receptor expression, and that leakiness of TVA receptors is dependent on the titer of TVA virus used. We concluded that a titer of 1.0-3.0 × 107 genomic copies per µl of the TVA virus is optimal for rabies tracing. Next, we successfully applied modified rabies virus tracing technology to map inputs to LepRb-expressing LH neurons. We discovered that other neurons in the LH itself, the periventricular hypothalamic nucleus (Pe), the posterior hypothalamic nucleus (PH), the bed nucleus of the stria terminalis (BNST), and the paraventricular hypothalamic nucleus (PVN) are the most prominent input areas to LepRb-expressing LH neurons.

A randomised, double-blind, sham-controlled trial of deep brain stimulation of the bed nucleus of the stria terminalis for treatment-resistant obsessive-compulsive disorder.

Deep brain stimulation (DBS) is a promising treatment for severe, treatment-resistant obsessive-compulsive disorder (OCD). Here, nine participants (four females, mean age 47.9 ± 10.7 years) were implanted with DBS electrodes bilaterally in the bed nucleus of the stria terminalis (BNST). Following a one-month postoperative recovery phase, participants entered a three-month randomised, double-blind, sham-controlled phase before a twelve-month period of open-label stimulation incorporating a course of cognitive behavioural therapy (CBT). The primary outcome measure was OCD symptoms as rated with the Yale-Brown Obsessive-Compulsive Scale (YBOCS). In the blinded phase, there was a significant benefit of active stimulation over sham (p = 0.025, mean difference 4.9 points). After the open phase, the mean reduction in YBOCS was 16.6 ± 1.9 points (χ2 (11) = 39.8, p = 3.8 × 10-5), with seven participants classified as responders. CBT resulted in an additive YBOCS reduction of 4.8 ± 3.9 points (p = 0.011). There were two serious adverse events related to the DBS device, the most severe of which was an infection during the open phase necessitating device explantation. There were no serious psychiatric adverse events related to stimulation. An analysis of the structural connectivity of each participant's individualised stimulation field isolated right-hemispheric fibres associated with YBOCS reduction. These included subcortical tracts incorporating the amygdala, hippocampus and stria terminalis, in addition to cortical regions in the ventrolateral and ventromedial prefrontal cortex, parahippocampal, parietal and extrastriate visual cortex. In conclusion, this study provides further evidence supporting the efficacy and tolerability of DBS in the region of the BNST for individuals with otherwise treatment-refractory OCD and identifies a connectivity fingerprint associated with clinical benefit.

MPEP Lowers Binge Drinking in Male and Female C57BL/6 Mice: Relationship with mGlu5/Homer2/Erk2 Signaling.

BACKGROUND: Metabotropic glutamate receptor 5 (mGlu5) plays an important role in excessive alcohol use and the mGlu5/Homer2/Erk2 signaling pathway has been implicated in binge drinking. The mGlu5 negative allosteric modulator (NAM) 2-methyl-6-(phenylethynyl)pyridine hydrochloride (MPEP) has been shown to reduce binge drinking in male mice, but less is known about its effect on female mice. Here, we sought to determine whether sex differences exists in the effects of MPEP on binge drinking and whether they relate to changes in the MPEP mGlu5/Homer2/Erk2 signaling. METHODS: We measured the dose-response effect of MPEP on alcohol consumption in male and female mice using the Drinking in the Dark (DID) paradigm to assess potential sex differences. To rule out possible confounds of MPEP on locomotion, we measured the effects of MPEP on locomotor activity and drinking simultaneously during DID. Lastly, to test whether MPEP-induced changes in alcohol consumption were related to changes in Homer2 or Erk2 expression, we performed qPCR using brain tissue acquired from mice that had undergone 7 days of DID. RESULTS: 30 mg/kg MPEP reduced binge alcohol consumption across female and male mice, with no sex differences in the dose-response relationship. Locomotor activity did not mediate the effects of MPEP on alcohol intake, but activity correlated with alcohol intake independent of MPEP. MPEP did not change the expression of Homer2 and Erk2 mRNA in the bed nucleus of the stria terminalis (BNST) or nucleus accumbens in mice whose drinking was reduced by MPEP, relative to saline. There was a positive relationship between alcohol intake and Homer2 expression in the BNST. CONCLUSIONS: MPEP reduced alcohol consumption during DID in male and female C57BL/6 mice but did not change Homer2/Erk2 expression. Locomotor activity did not mediate the effects of MPEP on alcohol intake, though it correlated with alcohol intake. Alcohol intake during DID predicted BNST Homer2 expression. These data provide support for the regulation of alcohol consumption by mGlu5 across sexes.

Projections from the dorsomedial division of the bed nucleus of the stria terminalis to hypothalamic nuclei in the mouse.

As stressful environment is a potent modulator of feeding, we seek in the present work to decipher the neuroanatomical basis for an interplay between stress and feeding behaviors. For this, we combined anterograde and retrograde tracing with immunohistochemical approaches to investigate the patterns of projections between the dorsomedial division of the bed nucleus of the stria terminalis (BNST), well connected to the amygdala, and hypothalamic structures such as the paraventricular (PVH) and dorsomedial (DMH), the arcuate (ARH) nuclei and the lateral hypothalamic areas (LHA) known to control feeding and motivated behaviors. We particularly focused our study on afferences to proopiomelanocortin (POMC), agouti-related peptide (AgRP), melanin-concentrating-hormone (MCH) and orexin (ORX) neurons characteristics of the ARH and the LHA, respectively. We found light to intense innervation of all these hypothalamic nuclei. We particularly showed an innervation of POMC, AgRP, MCH and ORX neurons by the dorsomedial and dorsolateral divisions of the BNST. Therefore, these results lay the foundation for a better understanding of the neuroanatomical basis of the stress-related feeding behaviors.

Extended-amygdala intrinsic functional connectivity networks: A population study.

Pre-clinical and human neuroimaging research implicates the extended-amygdala (ExtA) (including the bed nucleus of the stria terminalis [BST] and central nucleus of the amygdala [CeA]) in networks mediating negative emotional states associated with stress and substance-use behaviours. The extent to which individual ExtA structures form a functionally integrated unit is controversial. We utilised a large sample (n > 1,000 healthy young adult humans) to compare the intrinsic functional connectivity networks (ICNs) of the BST and CeA using task-free functional magnetic resonance imaging (fMRI) data from the Human Connectome Project. We assessed whether inter-individual differences within these ICNs were related to two principal components representing negative disposition and alcohol use. Building on recent primate evidence, we tested whether within BST-CeA intrinsic functional connectivity (iFC) was heritable and further examined co-heritability with our principal components. We demonstrate the BST and CeA to have discrete, but largely overlapping ICNs similar to previous findings. We found no evidence that within BST-CeA iFC was heritable; however, post hoc analyses found significant BST iFC heritability with the broader superficial and centromedial amygdala regions. There were no significant correlations or co-heritability associations with our principal components either across the ICNs or for specific BST-Amygdala iFC. Possible differences in phenotype associations across task-free, task-based, and clinical fMRI are discussed, along with suggestions for more causal investigative paradigms that make use of the now well-established ExtA ICNs.

Extrahypothalamic oxytocin neurons drive stress-induced social vigilance and avoidance.

Oxytocin increases the salience of both positive and negative social contexts and it is thought that these diverse actions on behavior are mediated in part through circuit-specific action. This hypothesis is based primarily on manipulations of oxytocin receptor function, leaving open the question of whether different populations of oxytocin neurons mediate different effects on behavior. Here we inhibited oxytocin synthesis in a stress-sensitive population of oxytocin neurons specifically within the medioventral bed nucleus of the stria terminalis (BNSTmv). Oxytocin knockdown prevented social stress-induced increases in social vigilance and decreases in social approach. Viral tracing of BNSTmv oxytocin neurons revealed fibers in regions controlling defensive behaviors, including lateral hypothalamus, anterior hypothalamus, and anteromedial BNST (BNSTam). Oxytocin infusion into BNSTam in stress naïve mice increased social vigilance and reduced social approach. These results show that a population of extrahypothalamic oxytocin neurons plays a key role in controlling stress-induced social anxiety behaviors.