Altered habenula to locus coeruleus functional connectivity in past anorexia nervosa suggests correlation with suicidality: a pilot study

The behavioral relevance of a modular organization in the lateral habenula

Behavioral strategies for survival rely on the updates the brain continuously makes based on the surrounding environment. External stimuli-neutral, positive, and negative-relay core information to the brain, where a complex anatomical network rapidly organizes actions, including approach or escape, and regulates emotions. Human neuroimaging and physiology in nonhuman primates, rodents, and teleosts suggest a pivotal role of the lateral habenula in translating external information into survival behaviors. Here, we review the literature describing how discrete habenular modules-reflecting the molecular signatures, anatomical connectivity, and functional components-are recruited by environmental stimuli and cooperate to prompt specific behavioral outcomes. We argue that integration of these findings in the context of valence processing for reinforcing or discouraging behaviors is necessary, offering a compelling model to guide future work.

Energy balance drives diurnal and nocturnal brain transcriptome rhythms

Plasticity in daily timing of activity has been observed in many species, yet the underlying mechanisms driving nocturnality and diurnality are unknown. By regulating how much wheel-running activity will be rewarded with a food pellet, we can manipulate energy balance and switch mice to be nocturnal or diurnal. Here, we present the rhythmic transcriptome of 21 tissues, including 17 brain regions, sampled every 4 h over a 24-h period from nocturnal and diurnal male CBA/CaJ mice. Rhythmic gene expression across tissues comprised different sets of genes with minimal overlap between nocturnal and diurnal mice. We show that non-clock genes in the suprachiasmatic nucleus (SCN) change, and the habenula was most affected. Our results indicate that adaptive flexibility in daily timing of behavior is supported by gene expression dynamics in many tissues and brain regions, especially in the habenula, which suggests a crucial role for the observed nocturnal-diurnal switch.

Habenular functional connections are associated with depression state and modulated by ketamine

BACKGROUND

Depression is a widespread mental health disorder with complex neurobiological underpinnings. The habenula, known as the 'anti-reward center', is thought to play a pivotal role in the pathophysiology of depression. This study aims to elucidate the association between the functional connections of the habenula and depression severity and to explore the modulation of these connections by ketamine.

METHODS

We studied 177 participants from a 7-T resting-state functional magnetic resonance imaging subset of the Human Connectome Project dataset to determine the associations between the functional connections of the habenula and depression. Additionally, we analyzed 60 depressed patients from our ketamine database to conduct a preliminary study on alterations in the functional connections of the habenula after ketamine infusions. We also investigated whether the baseline functional connectivity of the habenula is linked to subsequent improvement in depression.

RESULTS

We found that functional connections between the habenula and the substantia nigra, as well as the ventral tegmental area were negatively correlated with depression scores and elevated after ketamine infusions. Furthermore, the connection between the right habenula and the right substantia nigra was negatively associated with the improvement of depression.

LIMITATIONS

The Human Connectome Project dataset primarily consists of data from healthy participants, with varying levels of depression scores.

CONCLUSION

These results suggest that the habenula may facilitate depression by suppressing dopamine reward centers, and ketamine may relieve depression by disinhibiting these dopaminergic regions. This study may enhance our understanding of the neural underpinnings of depression and ketamine's antidepressant effects.

Norepinephrine system at the interface of attention and reward

Reward learning is key to survival for individuals. Attention plays an important role in the rapid recognition of reward cues and establishment of reward memories. Reward history reciprocally guides attention to reward stimuli. However, the neurological processes of the interplay between reward and attention remain largely elusive, due to the diversity of the neural substrates that participate in these two processes. In this review, we delineate the complex and differentiated locus coeruleus norepinephrine (LC-NE) system in relation to different behavioral and cognitive substrates of reward and attention. The LC receives reward related sensory, perceptual, and visceral inputs, releases NE, glutamate, dopamine and various neuropeptides, forms reward memories, drives attentional bias and selects behavioral strategies for reward. Preclinical and clinical studies have found that abnormalities in the LC-NE system are involved in a variety of psychiatric conditions marked by disturbed functions in reward and attention. Therefore, we propose that the LC-NE system is an important hub in the interplay between reward and attention as well as a critical therapeutic target for psychiatric disorders characterized by compromised functions in reward and attention.

Non-suicidal self-injury, suicidal thoughts and behaviors in individuals with an eating disorder relative to healthy and psychiatric controls: A systematic review and meta-analysis

OBJECTIVE

Eating disorders (ED) may be associated with an increased prevalence of non-suicidal self-injury (NSSI) and suicidal thoughts and behaviors (STBs) relative to healthy (HC) and psychiatric (PC) controls. However, precise estimates of differences in prevalence between individuals with EDs and controls are unclear. We compared the prevalence of NSSI, suicidal ideation (SI), suicide attempts (SA), and deaths by suicide in controls and individuals with EDs.

METHOD

We searched MEDLINE, PsycINFO, EMBASE, and CINAHL for peer-reviewed publications reporting the prevalence of NSSI and/or STBs in EDs and HC or PC group (PROSPERO: CRD42021286754). A series of random-effects meta-analyses were conducted to estimate pooled odds ratios (ORs) for NSSI, SI, SA, and death by suicide in EDs.

RESULTS

Across 32 studies, individuals with an ED had a significantly increased prevalence of NSSI (HC: OR = 6.85 [95% CI: 3.60, 13.04]; PC: OR = 2.74 [95% CI: 1.49, 5.06]), SI (HC: OR = 3.63 [95% CI: 2.43, 5.41]; PC: OR = 3.10 [95% CI: 2.01, 4.78]), and SA (HC: OR = 5.16 [95% CI: 4.27, 6.24]; PC: OR = 1.37 [95% CI: 0.37, 4.99]) relative to HC and PC groups. A 2.93-times increased odd of death by suicide did not achieve statistical significance. There was a high-level of heterogeneity between studies.

DISCUSSION

Our findings indicate that ED populations have an increased prevalence of NSSI, SI, and SA but not death by suicide compared to controls and emphasize the need for effective clinical strategies to address these behaviors in ED populations.

PUBLIC SIGNIFICANCE

This review provides evidence for an increased prevalence of non-suicidal self-injury, suicidal ideation, and suicide attempts in populations with eating disorders compared to controls. Our findings emphasize the need for effective clinical strategies to address these behaviors in patients with eating disorders.

The influence of the subcortex and brain stem on overeating: How advances in functional neuroimaging can be applied to expand neurobiological models to beyond the cortex

Functional neuroimaging has become a widely used tool in obesity and eating disorder research to explore the alterations in neurobiology that underlie overeating and binge eating behaviors. Current and traditional neurobiological models underscore the importance of impairments in brain systems supporting reward, cognitive control, attention, and emotion regulation as primary drivers for overeating. Due to the technical limitations of standard field strength functional magnetic resonance imaging (fMRI) scanners, human neuroimaging research to date has focused largely on cortical and basal ganglia effects on appetitive behaviors. The present review draws on animal and human research to highlight how neural signaling encoding energy regulation, reward-learning, and habit formation converge on hypothalamic, brainstem, thalamic, and striatal regions to contribute to overeating in humans. We also consider the role of regions such as the mediodorsal thalamus, ventral striatum, lateral hypothalamus and locus coeruleus in supporting habit formation, inhibitory control of food craving, and attentional biases. Through these discussions, we present proposals on how the neurobiology underlying these processes could be examined using functional neuroimaging and highlight how ultra-high field 7-Tesla (7 T) fMRI may be leveraged to elucidate the potential functional alterations in subcortical networks. Focus is given to how interactions of these regions with peripheral endocannabinoids and neuropeptides, such as orexin, could be explored. Technical and methodological aspects regarding the use of ultra-high field 7 T fMRI to study eating behaviors are also reviewed.

Chronic stress pathology and ketamine-induced alterations in functional connectivity in major depressive disorder: An abridged review of the clinical evidence

A paradigm shift in the conceptualization of the neurobiology of depression and the serendipitous discovery of ketamine's rapid-acting antidepressant (RAAD) effects has ushered in a new era of innovative research and novel drug development. Since the initial discovery of ketamine's RAAD effects, multiple studies have supported its short-term efficacy for fast-tracked improvements in treatment-resistant depression. Evidence from MRI studies have repeatedly demonstrated functional connectivity alterations in stress- and trauma-related disorders suggesting this may be a viable biomarker of chronic stress pathology (CSP). Human mechanistic studies further support this by coupling functional connectivity to ketamine's RAAD effects including connectivity to glutamate neurotransmission, ketamine to normalized connectivity, and these advantageous normalizations to symptom improvement/ketamine response. This review provides an abridged discussion of the suspected neurobiological underpinnings of ketamine's RAAD effects, highlighting ketamine-induced alterations in prefrontal, striatal, and anterior cingulate cortex functional connectivity in major depressive disorder. We present a model of CSP underscoring the role of synaptic loss and dysconnectivity and discuss how ketamine may be used both as (1) a treatment to restore and normalize these stress-induced neural alterations and (2) a tool to study potential biomarkers of CSP and treatment response. We conclude by noting challenges and future directions including heterogeneity, sex differences, the role of early life stress, and the need for proliferation of new methods, paradigms, and tools that will optimize signal and allow analyses at different levels of complexity, according to the needs of the question at hand, perhaps by thinking hierarchically about both clinical and biological phenotypes.

Altered Static and Dynamic Functional Connectivity of Habenula Associated With Suicidal Ideation in First-Episode, Drug-Naïve Patients With Major Depressive Disorder

Investigating the neurobiological mechanism of suicidal ideation (SI) in major depressive disorder (MDD) may be beneficial to prevent the suicidal behavior. Mounting evidence showed that habenula contributed to the etiology of MDD. The habenula is a key brain region that links the forebrain to midbrain, crucial for the processing of reward and aversion. The aim of the present study was to identify whether first-episode, drug-naive MDD patients with SI displayed altered habenula neural circuitry. Forty-three and 38 drug-naïve patients with first-episode MDD with or without SI (SI+/- group) and 35 healthy control subjects (HC) underwent resting-state functional magnetic resonance imaging. The whole-brain habenula static (sFC) and dynamic functional connectivity (dFC) were calculated to identify regions showing significant difference among these three groups followed by region of interest to region of interest post hoc analysis. For sFC, compared with SI- and HC groups, SI+ group showed decreased sFC from habenula to the precuneus and the inferior frontal gyrus. Patients with MDD displayed increased sFC from habenula to the putamen but decreased sFC to the precentral gyrus. For dFC, SI+ group showed increased dFC from habenula to the superior temporal gyrus, the precuneus, but decreased dFC to the lingual gyrus, the postcentral gyrus, when comparing with SI- and HC groups. Patients with MDD, regardless of SI, displayed decreased dFC from the habenula to the angular gyrus. These findings provide evidence that SI in first-episode, drug-naïve patients with MDD may be related to an abnormality in habenula neural circuitry, which may provide the theoretical basis of novel treatments.