A stress-sensitive frontostriatal circuit supporting effortful reward-seeking behavior

Mesoscale brain-wide fluctuation analysis: revealing ketamine's rapid antidepressant across multiple brain regions

Depression has been linked to cortico-limbic brain regions, and ketamine is known for its rapid antidepressant effects. However, how these brain regions encode depression collaboratively and how ketamine regulates these regions to exert its prompt antidepressant effects through mesoscale brain-wide fluctuations remain elusive. In this study, we used a multidisciplinary approach, including multi-region in vivo recordings in mice, chronic social defeat stress (CSDS), and machine learning, to construct a Mesoscale Brain-Wide Fluctuation Analysis platform (MBFA-platform). This platform analyzes the mesoscale brain-wide fluctuations of multiple brain regions from the perspective of local field potential oscillations and network dynamics. The decoder results demonstrate that our MBFA platform can accurately classify the Control/CSDS and ketamine/saline-treated groups based on neural oscillation and network activities among the eight brain regions. We found that multiple-region LFPs patterns are disrupted in CSDS-induced social avoidance, with the basolateral amygdala playing a key role. Ketamine primarily exerts the compensatory effects through network dynamics, contributing to its rapid antidepressant effect. These findings highlight the MBFA platform as an interdisciplinary tool for revealing mesoscale brain-wide fluctuations underlying complex emotional pathologies, providing insights into the etiology of psychiatry. Furthermore, the platform's evaluation capabilities present a novel approach for psychiatric therapeutic interventions.

A neuroimmune circuit mediates cancer cachexia-associated apathy

Cachexia, a severe wasting syndrome associated with inflammatory conditions, often leads to multiorgan failure and death. Patients with cachexia experience extreme fatigue, apathy, and clinical depression, yet the biological mechanisms underlying these behavioral symptoms and their relationship to the disease remain unclear. In a mouse cancer model, cachexia specifically induced increased effort-sensitivity, apathy-like symptoms through a cytokine-sensing brainstem-to-basal ganglia circuit. This neural circuit detects elevated interleukin-6 (IL-6) at cachexia onset and translates inflammatory signals into decreased mesolimbic dopamine, thereby increasing effort sensitivity. We alleviated these apathy-like symptoms by targeting key circuit nodes: administering an anti-IL-6 antibody treatment, ablating cytokine sensing in the brainstem, and optogenetically or pharmacologically boosting mesolimbic dopamine. Our findings uncovered a central neural circuit that senses systemic inflammation and orchestrates behavioral changes, providing mechanistic insights into the connection between chronic inflammation and depressive symptoms.

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

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

Ketamine rescues anhedonia by cell-type- and input-specific adaptations in the nucleus accumbens

Ketamine is recognized as a rapid and sustained antidepressant, particularly for major depression unresponsive to conventional treatments. Anhedonia is a common symptom of depression for which ketamine is highly efficacious, but the underlying circuits and synaptic changes are not well understood. Here, we show that the nucleus accumbens (NAc) is essential for ketamine's effect in rescuing anhedonia in mice subjected to chronic stress. Specifically, a single exposure to ketamine rescues stress-induced decreased strength of excitatory synapses on NAc-D1 dopamine receptor-expressing medium spiny neurons (D1-MSNs). Using a cell-specific pharmacology method, we establish the necessity of this synaptic restoration for the sustained therapeutic effects of ketamine on anhedonia. Examining causal sufficiency, artificially increasing excitatory synaptic strength onto D1-MSNs recapitulates the behavioral amelioration induced by ketamine. Finally, we used opto- and chemogenetic approaches to determine the presynaptic origin of the relevant synapses, implicating monosynaptic inputs from the medial prefrontal cortex and ventral hippocampus.

Exploration of brain imaging biomarkers in subthreshold depression patients across different ages: an ALE meta-analysis based on MRI studies

BACKGROUND

Structural neuroimaging findings in Subthreshold depression (StD) patients at different ages are highly heterogeneous. This study aims to investigate the pathophysiology of StD across different ages.

METHODS

Literature searches for MRI studies of StD were conducted in 11 databases, including PubMed and Embase, from database inception to June 18, 2024. An activation likelihood estimation (ALE) meta-analysis was performed on the studies across different ages.

RESULTS

A total of 24 studies were included. The results revealed that the significant convergent brain regions in StD patients across different ages were primarily located within the frontostriatal circuit. Age-related differences were observed. For adolescent patients, the significant convergent brain regions were the caudate, putamen, anterior cingulate cortex (ACC), and medial frontal gyrus (MFG). For young adult patients, the significant convergent brain regions were the inferior frontal gyrus, parahippocampal gyrus, insula, putamen, claustrum, and medial globus pallidus. For middle-aged and older patients, the significant convergent brain regions were the ACC, the MFG, and the superior frontal gyrus.

CONCLUSIONS

This study revealed that abnormalities in the frontostriatal circuit were neuroimaging features common in StD patients across different ages. Additionally, unique different brain regions were identified between age groups. These findings elucidated the mechanisms of StD and provided a theoretical basis for its prevention and treatment.

Illuminating the impact of stress: In vivo approaches to track stress-related neural adaptations

Stressful experiences can affect both daily life and long-term health outcomes in a variety of ways. Acute challenges may be adaptive, promoting arousal and enhancing memory and cognitive function. Importantly, however, chronic stress dysregulates the body's physiological regulatory mechanisms consisting of complex hormone interactions throughout the peripheral and central nervous systems. This disrupted signaling consequently alters the balance of synapse formation, maturation and pruning, processes which regulate neural communication, plasticity, learning, cognitive flexibility and adaptive behaviors - hallmarks of a healthy, functional brain. The chronically stressed brain state, therefore, is one which may be uniquely vulnerable. To understand the development of this state, how it is sustained and how behavior and neural function are transiently or indelibly impacted by it, we can turn to a number of advanced approaches in animal models which offer unprecedented insights. This has been the aim of my recent work within the field and the goal of my new independent research program. To achieve this, I have employed methods to uncover how key brain circuits integrate information to support motivated behaviors, how stress impacts their ability to perform this process and how best to operationalize behavioral readouts. Here I present an overview of research contributions that I find most meaningful for advancing our understanding of the impact of stress and propose new avenues which will guide my own framework to address the salient outstanding questions within the field.

Opioid use and abuse in adolescents and young adults; dealing with science, laws and ethics: Charming the COBRAS

The subject of substance use disorders in the pediatric population remains a disturbing conundrum for clinicians, researchers and society in general. Many of our youth are at risk of being damaged and even killed by drug addictions that result from the collision of rapidly developing as well as vulnerable central nervous systems encountering the current global drug addiction crisis. A major motif of this chemical calamity is opioid use disorder in adolescents and young adults that was stimulated by the 19th century identification of such highly addictive drugs as morphine, heroin and a non-opiate, cocaine. This analysis focuses on the pervasive presence of opioid drugs such as heroin and fentanyl that has become a major tragedy in the 21st century arising from an overall substance use and misuse phenomenon rampant in global society. Themes covered in this article include the history of addictive drugs in humans, diagnostic terms in use, the role of neurobiology in drug addiction, and current psychopharmacologic approaches to opioid overdose as well as addiction. Our youth are continuously confronted by dangers of high-risk behaviors including death and injury from opioid use disorders due to their central nervous system neuroplasticity as well as the widespread availability of these harmful chemicals. Healthcare professionals should actively assist our youth who unknowingly and even innocently encounter this deadly menace in the 21st century.

A cell type-specific mechanism driving the rapid antidepressant effects of transcranial magnetic stimulation

Repetitive transcranial magnetic stimulation (rTMS) is an emerging treatment for brain disorders, but its therapeutic mechanism is unknown. We developed a novel mouse model of rTMS with superior clinical face validity and investigated the neural mechanism by which accelerated intermittent theta burst stimulation (aiTBS) - the first rapid-acting rTMS antidepressant protocol - reversed chronic stress-induced behavioral deficits. Using fiber photometry, we showed that aiTBS drives distinct patterns of neural activity in intratelencephalic (IT) and pyramidal tract (PT) projecting neurons in dorsomedial prefrontal cortex (dmPFC). However, only IT neurons exhibited persistently increased activity during both aiTBS and subsequent depression-related behaviors. Similarly, aiTBS reversed stress-related loss of dendritic spines on IT, but not PT neurons, further demonstrating cell type-specific effects of stimulation. Finally, chemogenetic inhibition of dmPFC IT neurons during rTMS blocked the antidepressant-like behavioral effects of aiTBS. Thus, we demonstrate a prefrontal mechanism linking rapid aiTBS-driven therapeutic effects to cell type-specific circuit plasticity.

Microviridae bacteriophages influence behavioural hallmarks of food addiction via tryptophan and tyrosine signalling pathways

Food addiction contributes to the obesity pandemic, but the connection between how the gut microbiome is linked to food addiction remains largely unclear. Here we show that Microviridae bacteriophages, particularly Gokushovirus WZ-2015a, are associated with food addiction and obesity across multiple human cohorts. Further analyses reveal that food addiction and Gokushovirus are linked to serotonin and dopamine metabolism. Mice receiving faecal microbiota and viral transplantation from human donors with the highest Gokushovirus load exhibit increased food addiction along with changes in tryptophan, serotonin and dopamine metabolism in different regions of the brain, together with alterations in dopamine receptors. Mechanistically, targeted tryptophan analysis shows lower anthranilic acid (AA) concentrations associated with Gokushovirus. AA supplementation in mice decreases food addiction and alters pathways related to the cycle of neurotransmitter synthesis release. In Drosophila, AA regulates feeding behaviour and addiction-like ethanol preference. In summary, this study proposes that bacteriophages in the gut microbiome contribute to regulating food addiction by modulating tryptophan and tyrosine metabolism.

Identifying dysfunctional cell types and circuits in animal models for psychiatric disorders with calcium imaging

A central goal of neuroscience is to understand how the brain transforms external stimuli and internal bodily signals into patterns of activity that underlie cognition, emotional states, and behavior. Understanding how these patterns of activity may be disrupted in mental illness is crucial for developing novel therapeutics. It is well appreciated that psychiatric disorders are complex, circuit-based disorders that arise from dysfunctional activity patterns generated in discrete cell types and their connections. Recent advances in large-scale, cell-type specific calcium imaging approaches have shed new light on the cellular, circuit, and network-level dysfunction in animal models for psychiatric disorders. Here, we highlight a series of recent findings over the last ~10 years from in vivo calcium imaging studies that show how aberrant patterns of activity in discrete cell types and circuits may underlie behavioral deficits in animal models for several psychiatric disorders, including depression, anxiety, autism spectrum disorders, and schizophrenia. These advances in calcium imaging in pre-clinical models demonstrate the power of cell-type-specific imaging tools in understanding the underlying dysfunction in cell types, activity patterns, and neural circuits that may contribute to disease and provide new blueprints for developing more targeted therapeutics and treatment strategies.

Efficacy comparison of five antidepressants in treating anxiety and depression in cancer and non-cancer patients

Introduction

Cancer patients have a heightened susceptibility to anxiety and depressive disorders, which significantly impact the effectiveness of cancer treatments and long-term quality of life. This study aimed to compare the efficacy of different antidepressants in cancer and non-cancer patients.

Methods

A total of 610 patients diagnosed with depressive episodes and/or anxiety disorders were retrospectively included and divided into a cancer group and a non-cancer control group. Antidepressants used included escitalopram, duloxetine, sertraline, venlafaxine, and vortioxetine, combined with trazodone or not. The Patient Health Questionnaire-9 (PHQ-9) and the Generalized Anxiety Disorder Questionnaire-7 (GAD-7) scores were used to evaluate the efficacy after 4 weeks and 8 weeks of systematic antidepressants treatment.

Results

Compared to the non-cancer group, the cancer group had higher proportions of females, older individuals, and patients with poor sleep quality, while reporting fewer somatic symptoms at baseline (all p < 0.05). PHQ-9 and GAD-7 scores in cancer patients treated with antidepressants were significantly lower than baseline at week 4 and week 8 (all p < 0.05). The sertraline group demonstrated significantly less improvement in GAD-7 scores at week 4 and in both GAD-7 and PHQ-9 scores at week 8 compared to the escitalopram group, while duloxetine, venlafaxine, and vortioxetine showed comparable efficacy to escitalopram. Antidepressants combined with trazodone showed significant improvement in PHQ-9 scores at week 4 compared to those without trazodone. The gynecological cancer group showed significantly more improvement in GAD-7 and PHQ-9 scores at week 4 and 8 compared to breast cancer patients.

Conclusion

Antidepressant treatment in cancer patients with anxiety and depression is as effective as in non-cancer patients. The efficacy of escitalopram is comparable to duloxetine, venlafaxine, and vortioxetine, all of which outperformed sertraline in cancer patients.

Frontostriatal salience network expansion in individuals in depression

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

Neural substrates of predicting anhedonia symptoms in major depressive disorder via connectome-based modeling

MAIN PROBLEM

Anhedonia is a critical diagnostic symptom of major depressive disorder (MDD), being associated with poor prognosis. Understanding the neural mechanisms underlying anhedonia is of great significance for individuals with MDD, and it encourages the search for objective indicators that can reliably identify anhedonia.

METHODS

A predictive model used connectome-based predictive modeling (CPM) for anhedonia symptoms was developed by utilizing pre-treatment functional connectivity (FC) data from 59 patients with MDD. Node-based FC analysis was employed to compare differences in FC patterns between melancholic and non-melancholic MDD patients. The support vector machines (SVM) method was then applied for classifying these two subtypes of MDD patients.

RESULTS

CPM could successfully predict anhedonia symptoms in MDD patients (positive network: r = 0.4719, p < 0.0020, mean squared error = 23.5125, 5000 iterations). Compared to non-melancholic MDD patients, melancholic MDD patients showed decreased FC between the left cingulate gyrus and the right parahippocampus gyrus (p_bonferroni = 0.0303). This distinct FC pattern effectively discriminated between melancholic and non-melancholic MDD patients, achieving a sensitivity of 93.54%, specificity of 67.86%, and an overall accuracy of 81.36% using the SVM method.

CONCLUSIONS

This study successfully established a network model for predicting anhedonia symptoms in MDD based on FC, as well as a classification model to differentiate between melancholic and non-melancholic MDD patients. These findings provide guidance for clinical treatment.

The brain's go-getter circuit: Anterior cingulate cortex to nucleus accumbens and its disruption by stress

In this issue of Neuron, Fetcho, Parekh, et al.1 show that neurons in the anterior cingulate cortex (ACC) projecting to the nucleus accumbens (NAc) are essential for integrating reward and effort evaluation in mice, and that this circuit is sensitive to exposure to stress hormones.