Brain reward circuitry beyond the mesolimbic dopamine system: a neurobiological theory

Expression and localization of the neuropeptide Y-Y4 receptor in the chick spleen: mRNA upregulation by high ambient temperature

High ambient temperatures (HT) can increase diencephalic neuropeptide Y (NPY) expression, and central injection of NPY attenuates heat stress responses while inducing an antioxidative state in the chick spleen. However, there is a lack of knowledge about NPY receptor expression, and its regulation by HT, in the chick spleen. In the current study, male chicks were used to measure the expression of NPY receptors in the spleen and other immune organs under acute (30 vs. 40 ± 1°C for 3 h) or chronic (30 vs. 40 ± 1°C for 3 h/day for 3 days) exposure to HT and in response to central injection of NPY (47 pmol, 188 pmol, or 1 nmol). We found that NPY-Y4 receptor mRNA was expressed in the spleen, but not in other immune organs studied. Immunofluorescence staining revealed that NPY-Y4 receptors were localized in the splenic pulp. Furthermore, NPY-Y4 receptor mRNA increased in the chick spleen under both acute and chronic exposure to HT. Central NPY at two dose levels (47 and 188 pmol) and a higher dose (1 nmol) did not increase splenic NPY-Y4 receptor mRNA expression or splenic epinephrine under HT (35 ± 1°C), and significantly increased 3-methoxy-4-hydroxyphenylglycol (MHPG) concentrations under HT (40 ± 1°C). In conclusion, increased expression of NPY-Y4 receptor mRNA in the spleen under HT suggest that Y4 receptor may play physiological roles in response to HT in male chicks.

Neuropathic pain has sex-specific effects on oxycodone-seeking and non-drug-seeking ensemble neurons in the dorsomedial prefrontal cortex of mice

Approximately 50 million Americans suffer from chronic pain, and nearly a quarter of chronic pain patients have reported misusing opioid prescriptions. Repeated drug seeking is associated with reactivation of an ensemble of neurons sparsely scattered throughout the dorsomedial prefrontal cortex (dmPFC). Prior research has demonstrated that chronic pain increases intrinsic excitability of dmPFC neurons, which may increase the likelihood of reactivation during drug seeking. We tested the hypothesis that chronic pain would increase oxycodone-seeking behaviour and that the pain state would differentially increase intrinsic excitability in dmPFC drug-seeking ensemble neurons. TetTag mice self-administered intravenous oxycodone. After 7 days of forced abstinence, a drug-seeking session was performed, and the ensemble was tagged. Mice received spared nerve injury (SNI) to induce chronic pain during the period between the first and second seeking session. Following the second seeking session, we performed electrophysiology on individual neurons within the dmPFC to assess intrinsic excitability of the drug-seeking ensemble and non-ensemble neurons. SNI had no impact on sucrose seeking or intrinsic excitability of dmPFC neurons from these mice. In females, SNI increased oxycodone seeking and intrinsic excitability of non-ensemble neurons. In males, SNI had no impact on oxycodone seeking or neuron excitability. Data from females are consistent with clinical reports that chronic pain can promote drug craving and relapse and support the hypothesis that chronic pain itself may lead to neuroadaptations which promote opioid seeking.

Deep Brain Stimulation of the Medial Forebrain Bundle for Treatment-Resistant Depression: A Systematic Review Focused on the Long-Term Antidepressive Effect

OBJECTIVE

Major depression affects millions of people worldwide and has important social and economic consequences. Since up to 30% of patients do not respond to several lines of antidepressive drugs, deep brain stimulation (DBS) has been evaluated for the management of treatment-resistant depression (TRD). The superolateral branch of the medial forebrain bundle (slMFB) appears as a "hypothesis-driven target" because of its role in the reward-seeking system, which is dysfunctional in depression. Although initial results of slMFB-DBS from open-label studies were promising and characterized by a rapid clinical response, long-term outcomes of neurostimulation for TRD deserve particular attention. Therefore, we performed a systematic review focused on the long-term outcome of slMFB-DBS.

MATERIALS AND METHODS

A literature search using Preferred Reporting Items for Systematic Reviews and Meta-Analyses criteria was conducted to identify all studies reporting changes in depression scores after one-year follow-up and beyond. Patient, disease, surgical, and outcome data were extracted for statistical analysis. The Montgomery-Åsberg Depression Rating Scale (ΔMADRS) was used as the clinical outcome, defined as percentage reduction from baseline to follow-up evaluation. Responders' and remitters' rates were also calculated.

RESULTS

From 56 studies screened for review, six studies comprising 34 patients met the inclusion criteria and were analyzed. After one year of active stimulation, ΔMADRS was 60.7% ± 4%; responders' and remitters' rates were 83.8% and 61.5%, respectively. At the last follow-up, four to five years after the implantation, ΔMADRS reached 74.7% ± 4.6%. The most common side effects were stimulation related and reversible with parameter adjustments.

CONCLUSIONS

slMFB-DBS appears to have a strong antidepressive effect that increases over the years. Nevertheless, to date, the overall number of patients receiving implantations is limited, and the slMFB-DBS surgical technique seems to have an important impact on the clinical outcome. Further multicentric studies in a larger population are needed to confirm slMFB-DBS clinical outcomes.

Endogenous opioids in the olfactory tubercle and their roles in olfaction and quality of life

Olfactory dysfunctions decrease daily quality of life (QOL) in part by reducing the pleasure of eating. Olfaction plays an essential role in flavor sensation and palatability. The decreased QOL due to olfactory dysfunction is speculated to result from abnormal neural activities in the olfactory and limbic areas of the brain, as well as peripheral odorant receptor dysfunctions. However, the specific underlying neurobiological mechanisms remain unclear. As the olfactory tubercle (OT) is one of the brain's regions with high expression of endogenous opioids, we hypothesize that the mechanism underlying the decrease in QOL due to olfactory dysfunction involves the reduction of neural activity in the OT and subsequent endogenous opioid release in specialized subregions. In this review, we provide an overview and recent updates on the OT, the endogenous opioid system, and the pleasure systems in the brain and then discuss our hypothesis. To facilitate the effective treatment of olfactory dysfunctions and decreased QOL, elucidation of the neurobiological mechanisms underlying the pleasure of eating through flavor sensation is crucial.

Dynamic graph transformer network via dual-view connectivity for autism spectrum disorder identification

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder that requires objective and accurate identification methods for effective early intervention. Previous population-based methods via functional connectivity (FC) analysis ignore the differences between positive and negative FCs, which provide the potential information complementarity. And they also require additional information to construct a pre-defined graph. Meanwhile, two challenging demand attentions are the imbalance of performance caused by the class distribution and the inherent heterogeneity of multi-site data. In this paper, we propose a novel dynamic graph Transformer network based on dual-view connectivity for ASD Identification. It is based on the Autoencoders, which regard the input feature as individual feature and without any inductive bias. First, a dual-view feature extractor is designed to extract individual and complementary information from positive and negative connectivity. Then Graph Transformer network is innovated with a hot plugging K-Nearest Neighbor (KNN) algorithm module which constructs a dynamic population graph without any additional information. Additionally, we introduce the PolyLoss function and the Vrex method to address the class imbalance and improve the model's generalizability. The evaluation experiment on 1102 subjects from the ABIDE I dataset demonstrates our method can achieve superior performance over several state-of-the-art methods and satisfying generalizability for ASD identification.

Pathophysiological and therapeutic implications of neuropeptide S system in neurological disorders

Neuropeptide S (NPS) is a 20 amino acids-containing neuroactive molecule discovered by the reverse pharmacology method. NPS is detected in specific brain regions like the brainstem, amygdala, and hypothalamus, while its receptor (NPSR) is ubiquitously expressed in the central nervous system (CNS). Besides CNS, NPS and NPSR are also expressed in the peripheral nervous system. NPSR is a G-protein coupled receptor that primarily uses Gq and Gs signaling pathways to mediate the actions of NPS. In animal models of Parkinsonism and Alzheimer's disease, NPS exerts neuroprotective effects. NPS suppresses oxidative stress, anxiety, food intake, and pain, and promotes arousal. NPSR facilitates reward, reinforcement, and addiction-related behaviors. Genetic variation and single nucleotide polymorphism in NPSR are associated with depression, schizophrenia, rheumatoid arthritis, and asthma. NPS interacts with several neurotransmitters including glutamate, noradrenaline, serotonin, corticotropin-releasing factor, and gamma-aminobutyric acid. It also modulates the immune system via augmenting pro-inflammatory cytokines and plays an important role in the pathogenesis of rheumatoid arthritis and asthma. In the present review, we discussed the distribution profile of NPS and NPSR, signaling pathways, and their importance in the pathophysiology of various neurological disorders. We have also proposed the areas where further investigations on the NPS system are warranted.

Midfrontal conflict theta and parietal P300 are linked to a latent factor of DSM externalising disorders

Psychiatric illnesses form spectra rather than categories, with symptoms varying continuously across individuals, i.e., there is no clear break between health and disorder. Dimensional measures of behaviour and brain activity are promising targets for studying biological mechanisms that are common across disorders. Here, we assessed the extent to which neural measures of the sensitivity of the three biological systems in the reinforcement sensitivity theory (RST) could account for individual differences in a latent general factor estimated from symptom counts across externalising disorders (EXTs). RST explanatory power was pitted against reduced P300, a reliable indicator of externalising per previous research. We assessed 206 participants for DSM-5 EXTs (antisocial personality disorder, conduct disorder, attention-deficit/hyperactivity disorder, intermittent explosive disorder symptoms, alcohol use disorder, and cannabis use disorder). Of the final sample, 49% met diagnostic criteria for at least one of the EXTs. Electroencephalographic measures of the sensitivities of the behavioural activation system (BAS), the fight/flight/freeze system, and the behavioural inhibition system (BIS), as well as P300 were extracted from the gold bar-lemon and stop-signal tasks. As predicted, we found that low neural BIS sensitivity and low P300 were uniquely and negatively associated with our latent factor of externalising. Contrary to prediction, neural BAS/"dopamine" sensitivity was not associated with externalising. Our results provide empirical support for low BIS sensitivity and P300 as neural mechanisms common to disorders within the externalising spectrum; but, given the low N involved, future studies should seek to assess the replicability of our findings and, in particular, the differential involvement of the three RST systems.

Connectome-based prediction of decreased trust propensity in older adults with mild cognitive impairment: A resting-state functional magnetic resonance imaging study

Trust propensity (TP) relies more on social than economic rationality to transform the perceived probability of betrayal into positive reciprocity expectations in older adults with normal cognition. While deficits in social rationality have been observed in older adults with mild cognitive impairment (MCI), there is limited research on TP and its associated resting-state functional connectivity (RSFC) mechanisms in this population. To measure TP and related psychological functions (affect, motivation, executive cognition, and social cognition), MCI (n = 42) and normal healthy control (NHC, n = 115) groups completed a one-shot trust game and additional assessments of related psychological functions. RSFC associated with TP was analyzed using connectome-based predictive modeling (CPM) and lesion simulations. Our behavioral results showed that the MCI group trusted less (i.e., had lower TP) than the NHC group, with lower TP associated with higher sensitivity to the probability of betrayal in the MCI group. In the MCI group, only negative CPM models (RSFC negatively correlated with TP) significantly predicted TP, with a high salience network (SN) contribution. In contrast, in the NHC group, positive CPM models (RSFC positively correlated with TP) significantly predicted TP, with a high contribution from the default mode network (DMN). In addition, the total network strength of the NHC-specific positive network was lower in the MCI group than in the NHC group. Our findings demonstrated a decrease in TP in the MCI group compared to the NHC group, which is associated with deficits in social rationality (social cognition, associated with DMN) and increased sensitivity to betrayal (affect, associated with SN) in a trust dilemma. In conclusion, our study contributes to understanding MCI-related alterations in trust and their underlying neural mechanisms.

Dopamine encoding of novelty facilitates efficient uncertainty-driven exploration

When facing an unfamiliar environment, animals need to explore to gain new knowledge about which actions provide reward, but also put the newly acquired knowledge to use as quickly as possible. Optimal reinforcement learning strategies should therefore assess the uncertainties of these action-reward associations and utilise them to inform decision making. We propose a novel model whereby direct and indirect striatal pathways act together to estimate both the mean and variance of reward distributions, and mesolimbic dopaminergic neurons provide transient novelty signals, facilitating effective uncertainty-driven exploration. We utilised electrophysiological recording data to verify our model of the basal ganglia, and we fitted exploration strategies derived from the neural model to data from behavioural experiments. We also compared the performance of directed exploration strategies inspired by our basal ganglia model with other exploration algorithms including classic variants of upper confidence bound (UCB) strategy in simulation. The exploration strategies inspired by the basal ganglia model can achieve overall superior performance in simulation, and we found qualitatively similar results in fitting model to behavioural data compared with the fitting of more idealised normative models with less implementation level detail. Overall, our results suggest that transient dopamine levels in the basal ganglia that encode novelty could contribute to an uncertainty representation which efficiently drives exploration in reinforcement learning.

Alcohol and the dopamine system

The mesolimbic dopamine pathway plays a major role in drug reinforcement and is likely involved also in the development of drug addiction. Ethanol, like most addictive drugs, acutely activates the mesolimbic dopamine system and releases dopamine, and ethanol-associated stimuli also appear to trigger dopamine release. In addition, chronic exposure to ethanol reduces the baseline function of the mesolimbic dopamine system. The molecular mechanisms underlying ethanol´s interaction with this system remain, however, to be unveiled. Here research on the actions of ethanol in the mesolimbic dopamine system, focusing on the involvement of cystein-loop ligand-gated ion channels, opiate receptors, gastric peptides and acetaldehyde is briefly reviewed. In summary, a great complexity as regards ethanol´s mechanism(s) of action along the mesolimbic dopamine system has been revealed. Consequently, several new targets and possibilities for pharmacotherapies for alcohol use disorder have emerged.

[Addictions, complex pathologies in constant evolution]

Addiction is a dynamic field. Its ongoing changes reflect a persistent but evolving public health problem. Its evolution is reflected in subsequent classifications of mental illness. Numerous theories, inspired by psychoanalysis and neurobiology, address the development of the addictive process an many factors explain differences in susceptibility between individuals. In the last decade, behavioural addictions have been the subject of intense debate, leading to the inclusion of gambling disorder in the latest classification. The treatment of addictions is multifactorial and should take into account the specificities of each individual.

The central renin-angiotensin system: A genetic pathway, functional decoding, and selective target engagement characterization in humans

Accumulating evidence suggests that the brain renin angiotensin system (RAS) plays a pivotal role in the regulation of cognition and behavior as well as in the neuropathology of neurological and mental disorders. The angiotensin II type 1 receptor (AT1R) mediates most functional and neuropathology-relevant actions associated with the central RAS. However, an overarching comprehension to guide translation and utilize the therapeutic potential of the central RAS in humans is currently lacking. We conducted a comprehensive characterization of the RAS using an innovative combination of transcriptomic gene expression mapping, image-based behavioral decoding, and pre-registered randomized controlled discovery-replication pharmacological resting-state functional magnetic resonance imaging (fMRI) trials (N = 132) with a selective AT1R antagonist. The AT1R exhibited a particular dense expression in a subcortical network encompassing the thalamus, striatum, and amygdalo-hippocampal formation. Behavioral decoding of the AT1R gene expression brain map showed an association with memory, stress, reward, and motivational processes. Transient pharmacological blockade of the AT1R further decreased neural activity in subcortical systems characterized by a high AT1R expression, while increasing functional connectivity in the cortico-basal ganglia-thalamo-cortical circuitry. Effects of AT1R blockade on the network level were specifically associated with the transcriptomic signatures of the dopaminergic, opioid, acetylcholine, and corticotropin-releasing hormone signaling systems. The robustness of the results was supported in an independent pharmacological fMRI trial. These findings present a biologically informed comprehensive characterization of the central AT1R pathways and their functional relevance on the neural and behavioral level in humans.

From active affordance to active inference: vertical integration of cognition in the cerebral cortex through dual subcortical control systems

In previous papers, we proposed that the dorsal attention system's top-down control is regulated by the dorsal division of the limbic system, providing a feedforward or impulsive form of control generating expectancies during active inference. In contrast, we proposed that the ventral attention system is regulated by the ventral limbic division, regulating feedback constraints and error-correction for active inference within the neocortical hierarchy. Here, we propose that these forms of cognitive control reflect vertical integration of subcortical arousal control systems that evolved for specific forms of behavior control. The feedforward impetus to action is regulated by phasic arousal, mediated by lemnothalamic projections from the reticular activating system of the lower brainstem, and then elaborated by the hippocampus and dorsal limbic division. In contrast, feedback constraint-based on environmental requirements-is regulated by the tonic activation furnished by collothalamic projections from the midbrain arousal control centers, and then sustained and elaborated by the amygdala, basal ganglia, and ventral limbic division. In an evolutionary-developmental analysis, understanding these differing forms of active affordance-for arousal and motor control within the subcortical vertebrate neuraxis-may help explain the evolution of active inference regulating the cognition of expectancy and error-correction within the mammalian 6-layered neocortex.

Tyrosine Hydroxylase Knockdown at the Hypothalamic Supramammillary Nucleus Area Induces Obesity and Glucose Intolerance

INTRODUCTION

The supramammillary nucleus (SuMN) exerts influences on a wide range of brain functions including feeding and feeding-independent fuel metabolism. However, which specific neuronal type(s) within the SuMN manifest this influence has not been delineated. This study investigated the effect of SuMN tyrosine hydroxylase (TH) (rate-limiting enzyme in dopamine synthesis) knockdown (THx) on peripheral fuel metabolism.

METHODS

SuMN-THx was accomplished using a virus-mediated shRNA to locally knockdown TH gene expression at the SuMN. The impact of SuMN-THx was examined over 35-72 days in rats least prone to developing metabolic syndrome (MS) - female Sprague-Dawley rats resistant to the obesogenic effect of high fat diet (HFDr) and fed regular chow (RC) - upon body weight/fat, feeding, glucose tolerance, and insulin sensitivity. The influence of HFD, gender, and long-term response of SuMN-THx was subsequently investigated in female HFDr rats fed HFD, male HFDr rats fed RC, and female HFD-sensitive rats fed RC over 1 year, respectively.

RESULTS

SuMN-THx induced obesity and glucose intolerance, elevated plasma leptin and triglycerides, increased hepatic mRNA levels of gluconeogenic, lipogenic, and pro-inflammatory genes, reduced white adipose fatty acid oxidation rate, and altered plasma corticosterone level and hepatic circadian gene expression. Moreover, SuMN-THx increased feeding during the natural resting/fasting period and altered ghrelin feeding response suggesting ghrelin resistance. This MS-inducing effect was enhanced by HFD feeding, similarly observed in male rats and persisted over 1 year.

DISCUSSION/CONCLUSION

SuMN-THx induced long-term, gender-nonspecific, multiple pathophysiological changes leading to MS suggesting SuMN dopaminergic circuits communicating with other brain metabolism and behavior control centers modulate peripheral fuel metabolism.

Continuity and change in neural plasticity through embryonic morphogenesis, fetal activity-dependent synaptogenesis, and infant memory consolidation

There is an apparent continuity in human neural development that can be traced to venerable themes of vertebrate morphogenesis that have shaped the evolution of the reptilian telencephalon (including both primitive three-layered cortex and basal ganglia) and then the subsequent evolution of the mammalian six-layered neocortex. In this theoretical analysis, we propose that an evolutionary-developmental analysis of these general morphogenetic themes can help to explain the embryonic development of the dual divisions of the limbic system that control the dorsal and ventral networks of the human neocortex. These include the archicortical (dorsal limbic) Papez circuits regulated by the hippocampus that organize spatial, contextual memory, as well as the paleocortical (ventral limbic) circuits that organize object memory. We review evidence that these dorsal and ventral limbic divisions are controlled by the differential actions of brainstem lemnothalamic and midbrain collothalamic arousal control systems, respectively, thereby traversing the vertebrate subcortical neuraxis. These dual control systems are first seen shaping the phyletic morphogenesis of the archicortical and paleocortical foundations of the forebrain in embryogenesis. They then provide dual modes of activity-dependent synaptic organization in the active (lemnothalamic) and quiet (collothalamic) stages of fetal sleep. Finally, these regulatory systems mature to form the major systems of memory consolidation of postnatal development, including the rapid eye movement (lemnothalamic) consolidation of implicit memory and social attachment in the first year, and then-in a subsequent stage-the non-REM (collothalamic) consolidation of explicit memory that is integral to the autonomy and individuation of the second year of life.

Hypothalamic Supramammillary Control of Cognition and Motivation

The supramammillary nucleus (SuM) is a small region in the ventromedial posterior hypothalamus. The SuM has been relatively understudied with much of the prior focus being on its connection with septo-hippocampal circuitry. Thus, most studies conducted until the 21st century examined its role in hippocampal processes, such as theta rhythm and learning/memory. In recent years, the SuM has been "rediscovered" as a crucial hub for several behavioral and cognitive processes, including reward-seeking, exploration, and social memory. Additionally, it has been shown to play significant roles in hippocampal plasticity and adult neurogenesis. This review highlights findings from recent studies using cutting-edge systems neuroscience tools that have shed light on these fascinating roles for the SuM.

Retinal Changes in Parkinson's Disease: A Non-invasive Biomarker for Early Diagnosis

Parkinson's disease (PD) is caused due to degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNpc) which leads to the depletion of dopamine in the body. The lack of dopamine is mainly due to aggregation of misfolded α-synuclein which causes motor impairment in PD. Dopamine is also required for normal retinal function and the light-dark vision cycle. Misfolded α-synuclein present in inner retinal layers causes vision-associated problems in PD patients. Hence, individuals with PD also experience structural and functional changes in the retina. Mutation in LRRK2, PARK2, PARK7, PINK1, or SNCA genes and mitochondria dysfunction also play a role in the pathophysiology of PD. In this review, we discussed the different etiologies which lead to PD and future prospects of employing non-invasive techniques and retinal changes to diagnose the onset of PD earlier.

Altered reward processing in patients with lifelong premature ejaculation

Given that sexual behavior is usually pleasurable and highly rewarding, it is surprising that there is as yet no known research to empirically assess how premature ejaculation (PE) patients respond to the rewarding aspect of sexual behavior. This study was designed to address this issue by evaluating how these men respond to the anticipation and hedonic experience of sexual rewards in comparison to non-sexual rewards. Thirty lifelong PE patients and thirty healthy controls (HCs) performed the incentive delay task manipulating both erotic and monetary rewards. Compared to HCs, lifelong PE patients exhibited significantly faster RTs to erotic cues than to monetary cues during reward anticipation. Meanwhile, hedonic experience ratings after obtaining the actual reward showed that erotic rewards were rated as more pleasant than monetary rewards only by lifelong PE patients, which was driven by a decreased sensitivity to experienced monetary rewards in lifelong PE patients compared to HCs. These findings indicate the existence of dysfunctional reward processing in lifelong PE patients, which is characterized by increased incentive motivation elicited by sexual cues and reduced hedonic impact of nonsexual rewards. This study may offer an insightful clue regarding how PE is related to the abnormal regulation of the rewarding aspect of sexual behavior.

Dopaminergic dysfunction: Role for genetic & epigenetic testing in the new psychiatry

Reward Deficiency Syndrome (RDS), particularly linked to addictive disorders, costs billions of dollars globally and has resulted in over one million deaths in the United States (US). Illicit substance use has been steadily rising and in 2021 approximately 21.9% (61.2 million) of individuals living in the US aged 12 or older had used illicit drugs in the past year. However, only 1.5% (4.1 million) of these individuals had received any substance use treatment. This increase in use and failure to adequately treat or provide treatment to these individuals resulted in 106,699 overdose deaths in 2021 and increased in 2022. This article presents an alternative non-pharmaceutical treatment approach tied to gene-guided therapy, the subject of many decades of research. The cornerstone of this paradigm shift is the brain reward circuitry, brain stem physiology, and neurotransmitter deficits due to the effects of genetic and epigenetic insults on the interrelated cascade of neurotransmission and the net release of dopamine at the Ventral Tegmental Area -Nucleus Accumbens (VTA-NAc) reward site. The Genetic Addiction Risk Severity (GARS) test and pro-dopamine regulator nutraceutical KB220 were combined to induce "dopamine homeostasis" across the brain reward circuitry. This article aims to encourage four future actionable items: 1) the neurophysiologically accurate designation of, for example, "Hyperdopameism /Hyperdopameism" to replace the blaming nomenclature like alcoholism; 2) encouraging continued research into the nature of dysfunctional brainstem neurotransmitters across the brain reward circuitry; 3) early identification of people at risk for all RDS behaviors as a brain check (cognitive testing); 4) induction of dopamine homeostasis using "precision behavioral management" along with the coupling of GARS and precision Kb220 variants; 5) utilization of promising potential treatments include neuromodulating modalities such as Transmagnetic stimulation (TMS) and Deep Brain Stimulation(DBS), which target different areas of the neural circuitry involved in addiction and even neuroimmune agents like N-acetyl-cysteine.

Quinpirole, but not muscimol, infused into the nucleus accumbens disrupts prepulse inhibition of the acoustic startle in rhesus macaques

Sensorimotor gating is the ability to suppress motor responses to irrelevant sensory inputs. This response is disrupted in a range of neuropsychiatric disorders. Prepulse inhibition (PPI) of the acoustic startle response (ASR) is a form of sensorimotor gating in which a low-intensity prepulse immediately precedes a startling stimulus, resulting in an attenuation of the startle response. PPI is conserved across species and the underlying circuitry mediating this effect has been widely studied in rodents. However, recent work from our laboratories has shown an unexpected divergence between the circuitry controlling PPI in rodents as compared to macaques. The nucleus accumbens, a component of the basal ganglia, has been identified as a key modulatory node for PPI in rodents. The role of the nucleus accumbens in modulating PPI in primates has yet to be investigated. We measured whole-body PPI of the ASR in six rhesus macaques following (1) pharmacological inhibition of the nucleus accumbens using the GABAA agonist muscimol, and (2) focal application of the dopamine D2/3 agonist quinpirole (at 3 doses). We found that quinpirole, but not muscimol, infused into the nucleus accumbens disrupts prepulse inhibition in monkeys. These results differ from those observed in rodents, where both muscimol and quinpirole disrupt prepulse inhibition.

Interaction of Brain-Derived Neurotrophic Factor with the Effects of Chronic Methamphetamine on Prepulse Inhibition in Mice Is Independent of Dopamine D3 Receptors

The aim of the present study was to gain a better understanding of the role of brain-derived neurotrophic factor (BDNF) and dopamine D3 receptors in the effects of chronic methamphetamine (METH) on prepulse inhibition (PPI), an endophenotype of psychosis. We compared the effect of a three-week adolescent METH treatment protocol on the regulation of PPI in wildtype mice, BDNF heterozygous mice (HET), D3 receptor knockout mice (D3KO), and double-mutant mice (DM) with both BDNF heterozygosity and D3 receptor knockout. Chronic METH induced disruption of PPI regulation in male mice with BDNF haploinsufficiency (HET and DM), independent of D3 receptor knockout. Specifically, these mice showed reduced baseline PPI, as well as attenuated disruption of PPI induced by acute treatment with the dopamine receptor agonist, apomorphine (APO), or the glutamate NMDA receptor antagonist, MK-801. In contrast, there were no effects of BDNF heterozygosity or D3 knockout on PPI regulation in female mice. Chronic METH pretreatment induced the expected locomotor hyperactivity sensitisation, where female HET and DM mice also showed endogenous sensitisation. Differential sex-specific effects of genotype and METH pretreatment were observed on dopamine receptor and dopamine transporter gene expression in the striatum and frontal cortex. Taken together, these results show a significant involvement of BDNF in the long-term effects of METH on PPI, particularly in male mice, but these effects appear independent of D3 receptors. The role of this receptor in psychosis endophenotypes therefore remains unclear.

Nicotinic Acetylcholine Receptor Dysfunction in Addiction and in Some Neurodegenerative and Neuropsychiatric Diseases

The cholinergic system plays an essential role in brain development, physiology, and pathophysiology. Herein, we review how specific alterations in this system, through genetic mutations or abnormal receptor function, can lead to aberrant neural circuitry that triggers disease. The review focuses on the nicotinic acetylcholine receptor (nAChR) and its role in addiction and in neurodegenerative and neuropsychiatric diseases and epilepsy. Cholinergic dysfunction is associated with inflammatory processes mainly through the involvement of α7 nAChRs expressed in brain and in peripheral immune cells. Evidence suggests that these neuroinflammatory processes trigger and aggravate pathological states. We discuss the preclinical evidence demonstrating the therapeutic potential of nAChR ligands in Alzheimer disease, Parkinson disease, schizophrenia spectrum disorders, and in autosomal dominant sleep-related hypermotor epilepsy. PubMed and Google Scholar bibliographic databases were searched with the keywords indicated below.

Reward network dysfunction is associated with cognitive impairment after stroke

Stroke survivors not only suffer from severe motor, speech and neurocognitive deficits, but in many cases also from a "lack of pleasure" and a reduced motivational level. Especially apathy and anhedonic symptoms can be linked to a dysfunction of the reward system. Rewards are considered as important co-factor for learning, so the question arises as to why and how this affects the rehabilitation of stroke patients. We investigated reward behaviour, learning ability and brain network connectivity in acute (3-7d) mild to moderate stroke patients (n = 28) and age-matched healthy controls (n = 26). Reward system activity was assessed using the Monetary Incentive Delay task (MID) during magnetoencephalography (MEG). Coherence analyses were used to demonstrate reward effects on brain functional network connectivity. The MID-task showed that stroke survivors had lower reward sensitivity and required greater monetary incentives to improve performance and showed deficits in learning improvement. MEG-analyses showed a reduced network connectivity in frontal and temporoparietal regions. All three effects (reduced reward sensitivity, reduced learning ability and altered cerebral connectivity) were found to be closely related and differed strongly from the healthy group. Our results reinforce the notion that acute stroke induces reward network dysfunction, leading to functional impairment of behavioural systems. These findings are representative of a general pattern in mild strokes and are independent of the specific lesion localisation. For stroke rehabilitation, these results represent an important point to identify the reduced learning capacity after stroke and to implement individualised recovery exercises accordingly.

Effects of social isolation on 50-kHz ultrasonic vocalizations, affective state, cognition, and neurotransmitter concentrations in the ventral tegmental and locus coeruleus of adult rats

Vocal communication, cognition, and affective state are key features of sustained health and wellness, and because vocalizations are often socially-motivated, social experience likely plays a role in these behaviors. The monoaminergic systems of the ventral tegmental area (VTA) and the locus coeruleus (LC) are associated with social and reward processing, vocalization production, and neurotransmitter changes in response to environmental stressors. The effect of social isolation on these complex behaviors and the underlying neural mechanisms is relatively unknown. To add to this body of literature, we randomized adult male Long-Evans rats to control (housed with a cagemate) or isolated (housed individually) conditions and assayed ultrasonic vocalizations, cognition (novel object recognition test), anxiety (elevated plus maze) and anhedonia (sucrose preference test) at 2, 4, 6, 8, and 10 months of age. At 10 months, VTA and LC samples were assayed for dopamine, norepinephrine, and serotonin using high performance liquid chromatography. We tested the hypotheses that isolation 1) diminishes vocalizations and cognition, 2) increases anxiety and depression, and 3) increases levels of dopamine, norepinephrine, and serotonin in the VTA and LC. Results showed isolation significantly reduced vocalization tonality (signal-to-noise ratio) and increased maximum frequency. There were no significant findings for cognition, anxiety, or anhedonia. Dopamine and serotonin and their respective metabolites were significantly increased in the VTA in isolated rats. These findings suggest chronic changes to social condition such as isolation affects vocalization production and levels of VTA neurotransmitters.

Involvement of orexin-2 receptors in the CA1 region of the hippocampus in the extinction and reinstatement of methamphetamine-induced conditioned place preference in the rats

The present study, regarding the orexin receptors having a pivotal role in reward-related psychostimulant use disorder (PUD), aimed to investigate the role of orexin-2 (OX2) receptors in the CA1 region of the hippocampus (HPC) in the extinction and reinstatement of methamphetamine (METH)-induced conditioned place preference (CPP). In the first set of investigations, to determine the role of OX2 receptors in the extinction of METH-induced CPP, rats were daily given (during the extinction) bilaterally intra-CA1 region different doses of TCS OX2 29 (1, 3, 10, and 30 nmol/0.5 μl 12% DMSO) as the selective OX2 receptor antagonist. Then, to demonstrate the role of OX2 receptors in the reinstatement of METH-induced CPP after the extinction was established, each rat bilaterally received TCS OX2 29 at the same doses in the CA1 region before injection of the sub-threshold (priming) dose of METH (0.25 mg/kg, sc) on the reinstatement day. The data revealed that the administration of TCS OX2 29 in the CA1 region reduces the mean extinction latency and suppresses the reinstatement of METH-seeking behavior in extinguished rats. Additionally, the potency of TCS OX2 29 to inhibit the reinstatement phase was higher compared to the potency of this drug to modulate the extinction phase of METH-induced CPP. Accordingly, it could be concluded that the blockade of the OX2 receptors in this area might be an essential application and potential therapeutics in treating METH use disorder.

Functional connectivity based brain signatures of behavioral regulation in children with ADHD, DCD, and ADHD-DCD

Behavioral regulation problems have been associated with daily-life and mental health challenges in children with neurodevelopmental conditions such as attention-deficit/hyperactivity disorder (ADHD) and developmental coordination disorder (DCD). Here, we investigated transdiagnostic brain signatures associated with behavioral regulation. Resting-state fMRI data were collected from 115 children (31 typically developing (TD), 35 ADHD, 21 DCD, 28 ADHD-DCD) aged 7-17 years. Behavioral regulation was measured using the Behavior Rating Inventory of Executive Function and was found to differ between children with ADHD (i.e., children with ADHD and ADHD-DCD) and without ADHD (i.e., TD children and children with DCD). Functional connectivity (FC) maps were computed for 10 regions of interest and FC maps were tested for correlations with behavioral regulation scores. Across the entire sample, greater behavioral regulation problems were associated with stronger negative FC within prefrontal pathways and visual reward pathways, as well as with weaker positive FC in frontostriatal reward pathways. These findings significantly increase our knowledge on FC in children with and without ADHD and highlight the potential of FC as brain-based signatures of behavioral regulation across children with differing neurodevelopmental conditions.

Enhanced perceptual task performance without deprivation in mice using medial forebrain bundle stimulation

Perceptual decision-making tasks are essential to many fields of neuroscience. Current protocols generally reward deprived animals with water. However, balancing animals' deprivation level with their well-being is challenging, and trial number is limited by satiation. Here, we present electrical stimulation of the medial forebrain bundle (MFB) as an alternative that avoids deprivation while yielding stable motivation for thousands of trials. Using licking or lever press as a report, MFB animals learnt auditory discrimination tasks at similar speed to water-deprived mice. Moreover, they more reliably reached higher accuracy in harder tasks, performing up to 4,500 trials per session without loss of motivation. MFB stimulation did not impact the underlying sensory behavior since psychometric parameters and response times are preserved. MFB mice lacked signs of metabolic or behavioral stress compared with water-deprived mice. Overall, MFB stimulation is a highly promising tool for task learning because it enhances task performance while avoiding deprivation.

Different Features of a Metabolic Connectivity Map and the Granger Causality Method in Revealing Directed Dopamine Pathways: A Study Based on Integrated PET/MR Imaging

BACKGROUND AND PURPOSE

Exploring the directionality of neural information in the brain is important for understanding brain mechanisms and neurodisease development. Granger causality analysis and the metabolic connectivity map can be used to investigate directional transmission of information between brain regions, but their differences in depicting functional effective connectivity are not clear.

MATERIALS AND METHODS

Using the Monash rs-PET/MR imaging data set, we conducted Granger causality and metabolic connectivity map analyses of the dopamine reward circuit in the brain. The dopamine reward circuit is a well-known system consisting primarily of the bilateral orbital frontal cortex, caudate, nucleus accumbens, thalamus, and substantia nigra. We validated these circuit pathways using Granger causality and the metabolic connectivity map for identifying effective connectivities against a priori knowledge by testing the significance of directed pathways (P < .05, false discovery rate-corrected).

RESULTS

We found 3 types of effective connectivities in the dopamine reward circuit: long-range, neighborhood, and symmetric. Granger causality analysis revealed long-range connections in the orbital frontal cortex-caudate and orbital frontal cortex-nucleus accumbens regions. Metabolic connectivity map analysis revealed neighborhood connections in the nucleus accumbens-caudate, substantia nigra-thalamus, and thalamus-caudate regions. Metabolic connectivity map analysis also found symmetric connections in each of the bilateral nucleus accumbens, caudate, thalamus, and orbital frontal cortex-caudate regions. Different patterns in directional networks of the dopamine reward circuit were revealed by Granger causality and metabolic connectivity map analyses.

CONCLUSIONS

Granger causality analysis primarily identified bidirectional cortico-nucleus connections, while the metabolic connectivity map primarily identified direct connections among neighborhood and symmetric regions. The results of this study indicated that investigations of effective connectivities should use an appropriate analysis method depending on the purpose of the study.

Multidimensional Pain Modulation by Acupuncture Analgesia: The Reward Effect of Acupuncture on Pain Relief

Pain is an intrinsically unpleasant experience with features that protect an organism by promoting motivation and learning. Pain relief, a negative reinforcement of pain, is considered a reward and activates the brain's reward system. The reward circuit in the brain involves reward and pain. Acupuncture has a multidimensional and comprehensive regulating effect on chronic pain. However, the reward effect of acupuncture in relieving chronic pain and the mechanism of the brain reward circuit involved in acupuncture analgesia are not thoroughly studied. In this article, we have reviewed the definition of pain abnormalities and negative emotions in patients with chronic pain, the conceptual characteristics of analgesic reward, and the new progress in studying brain reward circuits and functions. Moreover, we have expounded on the critical clinical and scientific significance of studying the reward effect of acupuncture analgesia and related brain reward circuits, the pain mechanism obtained from human neuroimaging studies, and the survey results on the effects of acupuncture on reward/motivation circuits. Some viewpoints and suggestions on the reward effect of acupuncture analgesia and related reward circuits have been put forward to clarify the multidimensional characteristics and benign regulation of acupuncture analgesia. Studies on the reward effect of acupuncture in relieving chronic pain and the regulating effect of the brain reward loop on acupuncture analgesia help to deepen the clinical understanding of acupuncture analgesia, innovate the research concept of acupuncture analgesia, and provide help for further studies on the central mechanism of acupuncture in improving chronic pain in the future.

Class A and C GPCR Dimers in Neurodegenerative Diseases

Neurodegenerative diseases affect over 30 million people worldwide with an ascending trend. Most individuals suffering from these irreversible brain damages belong to the elderly population, with onset between 50 and 60 years. Although the pathophysiology of such diseases is partially known, it remains unclear upon which point a disease turns degenerative. Moreover, current therapeutics can treat some of the symptoms but often have severe side effects and become less effective in long-term treatment. For many neurodegenerative diseases, the involvement of G proteincoupled receptors (GPCRs), which are key players of neuronal transmission and plasticity, has become clearer and holds great promise in elucidating their biological mechanism. With this review, we introduce and summarize class A and class C GPCRs, known to form heterodimers or oligomers to increase their signalling repertoire. Additionally, the examples discussed here were shown to display relevant alterations in brain signalling and had already been associated with the pathophysiology of certain neurodegenerative diseases. Lastly, we classified the heterodimers into two categories of crosstalk, positive or negative, for which there is known evidence.

Aging of the mesolimbic tract in the human brain: A diffusion tensor imaging study

The mesolibic tract (MLT) is a dopaminergic tract that has been shown to play a role in regulating reward stimuli, including both incentive salience and social stimuli. In the current study, we examined the aging of MLT in normal human participants to explain human brain structures using diffusion tensor tractography (DTT). Fifty-seven healthy participants were recruited for this study and allocated to six groups based on their age. Diffusion tensor imaging (DTI) scanning was performed and MLTs were reconstructed using the probabilistic tractography method. MLTs were defined by selecting fibers passing through the seed and target regions of interest placed on the ventral segmental area and nucleus accumbens. A significant negative correlation was observed between age and the voxel number (VN) of MLT, while a positive correlation was observed between age and the apparent diffusion coefficient (ADC). The mean VN value of the MLT was significantly lower in the 60s and 70s age groups than in the 20s, 40s, and 50s (P < .05). The mean ADC value of the MLT was significantly higher in the 60s and 70s groups than in the 20s, 30s, and 40s, 50s groups (P < .05). We found that aging of the MLT began in the 20s or 30s and progressed steadily throughout life until the 60s, when it exhibited significant degeneration. We believe this affect may play a role in the decline of memory and social interaction with aging in normal participants.

Neural correlates and potential targets for the contribution of orexin to addiction in cortical and subcortical areas

The orexin (hypocretin) is one of the hypothalamic neuropeptides that plays a critical role in some behaviors including feeding, sleep, arousal, reward processing, and drug addiction. This variety of functions can be described by a united function for orexins in translating states of heightened motivation, for example during physiological requirement states or following exposure to reward opportunities, into planned goal-directed behaviors. An addicted state is characterized by robust activation of orexin neurons from the environment, which triggers downstream circuits to facilitate behavior directed towards obtaining the drug. Two orexin receptors 1 (OX1R) and 2 (OX2R) are widely distributed in the brain. Here, we will introduce and describe the cortical and subcortical brain areas involved in addictive-like behaviors and the impact of orexin on addiction.

Prediction of the gait function using the nigrostriatal and corticoreticulospinal tracts of the affected hemisphere in a cerebral infarct: A diffusion tensor imaging study

Prognosis predictability of the nigrostriatal tract (NST) and corticoreticulospinal tract (CRT) of affected hemisphere at early stage for gait function at chronic stage were investigated using diffusion tensor tractography (DTT) in patients with a cerebral infarction. Thirty consecutive patients with middle cerebral artery (MCA) territory infarction were recruited. Functional ambulation category (FAC) was used to evaluate the gait function at chronic stage. Fractional anisotropy (FA) and tract volume (TV) of ipsilesional NST and ipsilesional CRT were determined to be DTT parameters at early stage. FAC score at chronic stage showed strong positive correlations with TVs of ipsilesional NST and ipsilesional CRT at early stage (ipsilesional NST R = 0.786; ipsilesional CRT R = 0.821; P < .05). According to regression model, FAC score at chronic stage was positively related to TVs of ipsilesional NST and ipsilesional CRT at early stage (Adjusted R2 = 0.700, F = 34.905, P < .05). FAC score at chronic stage was associated more positively with TV of ipsilesional CRT (β = 0.532) than that of ipsilesional NST (β = 0.362). Ipsilesional NST and ipsilesional CRT at early stage had prognosis predictability for gait function at chronic stage in patients with an MCA infarction. Moreover, ipsilesional CRT had stronger predictability than ipsilesional NST.

Chronic early-life lead exposure sensitizes adolescent rats to cocaine: Role of the dopaminergic system

Exposure to heavy metals has been associated with psychiatric disorders and recent studies suggest an association between childhood lead (Pb²⁺) intoxication and schizophrenia (SZ). In animal models, Pb²⁺ exposure recapitulates key neuropathological and dopaminergic system alterations present in SZ. Given the high comorbidity of mental disorders such as SZ and substance abuse, coupled with evidence showing that Pb²⁺ exposure affects addiction circuits, we hypothesized that early life Pb²⁺ exposure could sensitize neuronal systems relevant to SZ and substance abuse. To this goal, we examined the effects of chronic developmental Pb²⁺ exposure on the acute locomotor response to cocaine (0, 5, and 15 mg kg^–1) and behavioral sensitization. We also examined the role of the dopaminergic system in the psychostimulant effects of cocaine, and measured D1-dopamine receptor (D1R) levels in the rat brain using [³H]-SCH23390 quantitative receptor autoradiography, as well as the ability of the D1R antagonist SCH23390 to block the cocaine effects on locomotor activation. These studies were performed in male and female rats at different developmental ages consisting of juveniles (postnatal, PN14), early-adolescent (PN28), late adolescent (PN50), and adults (PN120). Our results show that chronic developmental Pb²⁺ exposure increases the acute locomotor response to the higher dose of cocaine in Pb²⁺-exposed male adolescent (PN28 and PN50) rats, and to the lower dose of cocaine in adolescent female rats. No changes in the locomotor activity were detected in adult rats. Behavioral sensitization experiments showed a sustained sensitization in early adolescent Pb²⁺-exposed male but not female rats. The cocaine-induced effects on locomotor activity were abrogated by injection of a D1R antagonist suggesting the involvement of this dopamine receptor subtype. Furthermore, Pb²⁺-induced increases D1R levels in several brain regions were prominent in juveniles and early adolescence but not in late adolescence or in adults. In summary, early chronic developmental Pb²⁺ exposure results in age and sex-dependent effect on the locomotor response to cocaine, suggesting differential susceptibilities to the neurotoxic effects of Pb²⁺ exposure. Our data provides further support to the notion that Pb²⁺ exposure is an environmental risk factor for psychiatric disorders and substance abuse.

Brain Morphology Predictors of Alcohol, Tobacco, and Cannabis Use in Adolescence: A Systematic Review

In the last decade, extensive research has emerged on the predictive value of brain morphology for substance use initiation and related problems during adolescence. This systematic review provides an overview of longitudinal studies on pre-existing brain variations and later initiation of alcohol, tobacco, and cannabis use (N = 18). Adolescent structural neuroimaging studies that started before substance use initiation suggest that a smaller anterior cingulate cortex (ACC) volume, thicker or smaller superior frontal gyrus, and larger nucleus accumbens (NAcc) volume are associated with future alcohol use. Also, both smaller and larger orbitofrontal cortex (OFC) volumes were associated with future cannabis and combined alcohol/cannabis use. Smaller amygdala volumes were related to future daily tobacco smoking. These findings could point to specific vulnerabilities for adolescent substance use, as these brain areas are involved in cognitive control (ACC), reward (NAcc), motivation (OFC), and emotional memory (amygdala). However, the reported findings were inconsistent in directionality and laterality, and the largest study on alcohol use predictors reported null findings. Therefore, large population-based longitudinal studies should investigate the robustness and mechanisms of these associations. We suggested future research directions regarding sample selection, timing of baseline and follow-up measurements, and a harmonization approach of study methods.

Becoming a mother shifts the activity of the social and motivation brain networks in mice

During pregnancy hormones increase motivated pup-directed behaviors. We here analyze hormone-induced changes in brain activity, by comparing cFos-immunoreactivity in the sociosexual (SBN) and motivation brain networks (including medial preoptic area, MPO) of virgin versus late-pregnant pup-naïve female mice exposed to pups or buttons (control). Pups activate more the SBN than buttons in both late-pregnant and virgin females. By contrast, pregnancy increases pup-elicited activity in the motivation circuitry (e.g. accumbens core) but reduces button-induced activity and, consequently, button investigation. Principal components analysis supports the identity of the social and motivation brain circuits, placing the periaqueductal gray between both systems. Linear discriminant analysis of cFos-immunoreactivity in the socio-motivational brain network predicts the kind of female and stimulus better than the activity of the MPO alone; this suggests that the neuroendocrinological basis of social (e.g. maternal) behaviors conforms to a neural network model, rather than to distinct hierarchical linear pathways for different behaviors.

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Pups activate the sociosexual brain network of females more than nonsocial objects

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Pregnancy boosts motivation for pups and reduces incentive salience of buttons

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During pregnancy, specific circuits govern decision of caring or attacking pups

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The socio-motivational brain works as a network rather than a labelled-line circuit

Still Wanting to Win: Reward System Stability in Healthy Aging

Healthy aging is accompanied by multi-faceted changes. Especially within the brain, healthy aging exerts substantial impetus on core parts of cognitive and motivational networks. Rewards comprise basic needs, such as food, sleep, and social contact. Thus, a functionally intact reward system remains indispensable for elderly people to cope with everyday life and adapt to their changing environment. Research shows that reward system function is better preserved in the elderly than most cognitive functions. To investigate the compensatory mechanisms providing reward system stability in aging, we employed a well-established reward paradigm (Monetary Incentive Delay Task) in groups of young and old participants while undergoing EEG measurement. As a new approach, we applied EEG connectivity analyses to assess cortical reward-related network connectivity. At the behavioral level, our results confirm that the function of the reward system is preserved in old age. The mechanisms identified for maintaining reward system function in old age do not fit into previously described models of cognitive aging. Overall, older adults exhibit lower reward-related connectivity modulation, higher reliance on posterior and right-lateralized brain areas than younger adults, and connectivity modulation in the opposite direction than younger adults, with usually greater connectivity during non-reward compared to reward conditions. We believe that the reward system has unique compensatory mechanisms distinct from other cognitive functions, probably due to its etymologically very early origin. In summary, this study provides important new insights into cortical reward network connectivity in healthy aging.

Melanocortin Signaling Connecting Systemic Metabolism With Mood Disorders

Obesity and mood disorders are often overlapping pathologies that are prevalent public health concerns. Many studies have indicated a positive correlation between depression and obesity, although weight loss and decreased appetite are also recognized as features of depression. Accordingly, DSM-5 defines two subtypes of depression associated with changes in feeding: melancholic depression, characterized by anhedonia and associated with decreased feeding and appetite; and atypical depression, characterized by fatigue, sleepiness, hyperphagia, and weight gain. The central nervous system plays a key role in the regulation of feeding and mood, thus suggesting that overlapping neuronal circuits may be involved in their modulation. However, these circuits have yet to be completely characterized. The central melanocortin system, a circuitry characterized by the expression of specific peptides (pro-opiomelanocortins, agouti-related protein, and neuropeptide Y) and their melanocortin receptors, has been shown to be a key player in the regulation of feeding. In addition, the melanocortin system has also been shown to affect anxiety and depressive-like behavior, thus suggesting a possible role of the melanocortin system as a biological substrate linking feeding and depression. However, more studies are needed to fully understand this complex system and its role in regulating metabolic and mood disorders. In this review, we will discuss the current literature on the role of the melanocortin system in human and animal models in feeding and mood regulation, providing evidence of the biological interplay between anxiety, major depressive disorders, appetite, and body weight regulation.

Deep brain stimulation of the "medial forebrain bundle": sustained efficacy of antidepressant effect over years

Deep brain stimulation (DBS) to the superolateral branch of the medial forebrain bundle (MFB) has emerged as a quite efficacious therapy for treatment resistant depression (TRD), leading to rapid antidepressant effects. In this study, we complete our assessment of our first 10 enrolled patients throughout one year post-implantation, showing sustained antidepressant effect up to 5 years. The primary outcome measure was a 50% reduction in Montgomery-Åsberg Depression Rating Scale (MADRS) score, which was interpreted as a response. Deterministic fiber tracking was used to individually map the target area. An insertional effect was seen during the 4-week sham stimulation phase (29% mean MADRS reduction, p = 0.02). However, after 2 weeks of initiating stimulation, five patients met response criteria (47% mean MADRS reduction, p < 0.001). One patient withdrew from study participation at 6 weeks. Twelve weeks after initiating stimulation, six of nine remaining patients had a >50% decrease in MADRS scores relative to baseline (52% mean MADRS reduction, p = 0.001); these same six patients continued to meet response criteria at 52 weeks (63% overall mean MADRS reduction, p < 0.001). Four of five patients who achieved the 5-year time point analysis continued to be responders (81% mean MADRS reduction, p < 0.001). Evaluation of modulated fiber tracts reveals significant common prefrontal/orbitofrontal connectivity to the target region in all responders. Key points learned from this study that we can incorporate in future protocols to better elucidate the effect of this therapy are a longer blinded sham stimulation phase and use of scheduled discontinuation concomitant with functional imaging.

Neuropathological investigation of patients with prolonged anorexia nervosa

OBJECTIVES

Recent neuroimaging studies have indicated that the mesolimbic pathway, known to work as reward neuronal circuitry, regulates cognitive-behavioral flexibility in prolonged anorexia nervosa (AN). Although AN is associated with the highest mortality rate among psychiatric disorders, there have been few neuropathological studies on this topic. This study aims to identify alterations of the reward circuitry regions, especially in the nucleus accumbens (NAcc), using AN brain tissues.

METHODS

The neuronal networks in AN cases and controls were examined by immunohistochemistry directed at tyrosine hydroxylase (TH; dopaminergic neuron marker) and glial fibrillary acidic protein (GFAP; astrocyte marker). We also immunochemically analyzed frozen samples presenting astrogliosis, especially in the NAcc and striatum.

RESULTS

Histologically, neuronal deformation with cytoplasmic shrinkage was seen in reward-related brain regions, such as the orbitofrontal cortex/anterior cingulate cortex. The NAcc showed massive GFAP-positive astrocytes and dot-like protrusions of astrocytes in the shell compartment. In the shell, TH and GFAP immunoreactivities revealed prominent astrogliosis within striosomes, which receive projection from the ventral tegmental area (VTA). The numbers of GFAP-positive astrocytes in the NAcc (P = 0.0079) and VTA (P = 0.0025) of AN cases were significantly higher than those of controls. Strongly immunoreactive 18 to 25 kDa bands, which might represent degradation products, were detected only in the NAcc of AN cases. Clinically, all cases presented cognitive rigidity, which might reflect a deficit of the reward pathway.

CONCLUSION

Our findings suggest impaired dopaminergic innervation between the NAcc and VTA in AN. Functional dysconnectivity in the reward-related network might induce neuropsychiatric symptoms associated with AN.

Relationship of the Nigrostriatal Tract with the Motor Function and the Corticospinal Tract in Chronic Hemiparetic Stroke Patients: A Diffusion Tensor Imaging Study

This study investigated the relationship of the nigrostriatal tract (NST) with motor function and the corticospinal tract (CST) using diffusion tensor tractography in chronic hemiparetic stroke patients. Forty-three consecutive patients with putaminal hemorrhage in the chronic stage were recruited. The Motricity Index was used to evaluate the motor function of affected hemiparetic extremities. The fractional anisotropy and the tract volume of ipsilesional NST and ipsilesional CST were acquired. The tract volume (Rho = 0.824) of ipsilesional NST and fractional anisotropy (r = 0.682) and the tract volume (Rho = 0.886) of ipsilesional CST showed a strong positive correlation with the Motricity Index score. The fractional anisotropy of ipsilesional NST showed moderate positive correlations with the fractional anisotropy (r = 0.449) and tract volume (Rho = 0.353) of ipsilesional CST. The tract volume of ipsilesional NST showed strong positive correlations with the fractional anisotropy (Rho = 0.716) and the tract volume (Rho = 0.799) of ipsilesional CST. The regression model showed that the tract volumes of ipsilesional NST and ipsilesional CST were positively associated with the Motricity Index score (Adjusted R² = 0.763, F = 45.998). Mediation analysis showed that the tract volume of ipsilesional CST partially mediated the effects of the tract volume of ipsilesional NST on the Motricity Index score (z = 3.34). A close relationship was found between ipsilesional NST and the motor function of affected extremities in chronic hemiparetic patients with putaminal hemorrhage. Moreover, ipsilesional NST influenced the motor function of affected extremities indirectly through ipsilesional CST.

"The Heart Asks Pleasure First"-Conceptualizing Psychiatric Diseases as MAINTENANCE Network Dysfunctions through Insights from slMFB DBS in Depression and Obsessive-Compulsive Disorder

More than a decade ago, deep brain stimulation (DBS) of the superolateral medial forebrain bundle (slMFB), as part of the greater MFB system, had been proposed as a putative yet experimental treatment strategy for therapy refractory depression (TRD) and later for obsessive-compulsive disorders (OCD). Antidepressant and anti-OCD efficacy have been shown in open case series and smaller trials and were independently replicated. The MFB is anato-physiologically confluent with the SEEKING system promoting euphoric drive, reward anticipation and reward; functions realized through the mesocorticolimbic dopaminergic system. Growing clinical experience concerning surgical and stimulation aspects from a larger number of patients shows an MFB functionality beyond SEEKING and now re-informs the scientific rationale concerning the MFB's (patho-) physiology. In this white paper, we combine observations from more than 75 cases of slMFB DBS. We integrate these observations with a selected literature review to provide a new neuroethological view on the MFB. We here formulate a re-interpretation of the MFB as the main structure of an integrated SEEKING/MAINTENANCE circuitry, allowing for individual homeostasis and well-being through emotional arousal, basic and higher affect valence, bodily reactions, motor programing, vigor and flexible behavior, as the basis for the antidepressant and anti-OCD efficacy.

Medial prefrontal cortex and anteromedial thalamus interaction regulates goal-directed behavior and dopaminergic neuron activity

The prefrontal cortex is involved in goal-directed behavior. Here, we investigate circuits of the PFC regulating motivation, reinforcement, and its relationship to dopamine neuron activity. Stimulation of medial PFC (mPFC) neurons in mice activated many downstream regions, as shown by fMRI. Axonal terminal stimulation of mPFC neurons in downstream regions, including the anteromedial thalamic nucleus (AM), reinforced behavior and activated midbrain dopaminergic neurons. The stimulation of AM neurons projecting to the mPFC also reinforced behavior and activated dopamine neurons, and mPFC and AM showed a positive-feedback loop organization. We also found using fMRI in human participants watching reinforcing video clips that there is reciprocal excitatory functional connectivity, as well as co-activation of the two regions. Our results suggest that this cortico-thalamic loop regulates motivation, reinforcement, and dopaminergic neuron activity.

Reciprocal processes of sensory perception and social bonding: an integrated social-sensory framework of social behavior

Organisms filter the complexity of natural stimuli through their individual sensory and perceptual systems. Such perceptual filtering is particularly important for social stimuli. A shared "social umwelt" allows individuals to respond appropriately to the expected diversity of cues and signals during social interactions. In this way, the behavioral and neurobiological mechanisms of sociality and social bonding cannot be disentangled from perceptual mechanisms and sensory processing. While a degree of embeddedness between social and sensory processes is clear, our dominant theoretical frameworks favor treating the social and sensory processes as distinct. An integrated social-sensory framework has the potential to greatly expand our understanding of the mechanisms underlying individual variation in social bonding and sociality more broadly. Here we leverage what is known about sensory processing and pair bonding in two common study systems with significant species differences in their umwelt (rodent chemosensation and avian acoustic communication). We primarily highlight that (1) communication is essential for pair bond formation and maintenance, (2) the neural circuits underlying perception, communication and social bonding are integrated, and (3) candidate neuromodulatory mechanisms that regulate pair bonding also impact communication and perception. Finally, we propose approaches and frameworks that more fully integrate sensory processing, communication, and social bonding across levels of analysis: behavioral, neurobiological, and genomic. This perspective raises two key questions: (1) how is social bonding shaped by differences in sensory processing?, and (2) to what extent is sensory processing and the saliency of signals shaped by social interactions and emerging relationships?

Reward Deficiency Syndrome (RDS) Surprisingly Is Evolutionary and Found Everywhere: Is It "Blowin' in the Wind"?

Reward Deficiency Syndrome (RDS) encompasses many mental health disorders, including a wide range of addictions and compulsive and impulsive behaviors. Described as an octopus of behavioral dysfunction, RDS refers to abnormal behavior caused by a breakdown of the cascade of reward in neurotransmission due to genetic and epigenetic influences. The resultant reward neurotransmission deficiencies interfere with the pleasure derived from satisfying powerful human physiological drives. Epigenetic repair may be possible with precision gene-guided therapy using formulations of KB220, a nutraceutical that has demonstrated pro-dopamine regulatory function in animal and human neuroimaging and clinical trials. Recently, large GWAS studies have revealed a significant dopaminergic gene risk polymorphic allele overlap between depressed and schizophrenic cohorts. A large volume of literature has also identified ADHD, PTSD, and spectrum disorders as having the known neurogenetic and psychological underpinnings of RDS. The hypothesis is that the true phenotype is RDS, and behavioral disorders are endophenotypes. Is it logical to wonder if RDS exists everywhere? Although complex, “the answer is blowin’ in the wind,” and rather than intangible, RDS may be foundational in species evolution and survival, with an array of many neurotransmitters and polymorphic loci influencing behavioral functionality.

Multiple Aspects of Inappropriate Action of Renin-Angiotensin, Vasopressin, and Oxytocin Systems in Neuropsychiatric and Neurodegenerative Diseases

The cardiovascular system and the central nervous system (CNS) closely cooperate in the regulation of primary vital functions. The autonomic nervous system and several compounds known as cardiovascular factors, especially those targeting the renin-angiotensin system (RAS), the vasopressin system (VPS), and the oxytocin system (OTS), are also efficient modulators of several other processes in the CNS. The components of the RAS, VPS, and OTS, regulating pain, emotions, learning, memory, and other cognitive processes, are present in the neurons, glial cells, and blood vessels of the CNS. Increasing evidence shows that the combined function of the RAS, VPS, and OTS is altered in neuropsychiatric/neurodegenerative diseases, and in particular in patients with depression, Alzheimer's disease, Parkinson's disease, autism, and schizophrenia. The altered function of the RAS may also contribute to CNS disorders in COVID-19. In this review, we present evidence that there are multiple causes for altered combined function of the RAS, VPS, and OTS in psychiatric and neurodegenerative disorders, such as genetic predispositions and the engagement of the RAS, VAS, and OTS in the processes underlying emotions, memory, and cognition. The neuroactive pharmaceuticals interfering with the synthesis or the action of angiotensins, vasopressin, and oxytocin can improve or worsen the effectiveness of treatment for neuropsychiatric/neurodegenerative diseases. Better knowledge of the multiple actions of the RAS, VPS, and OTS may facilitate programming the most efficient treatment for patients suffering from the comorbidity of neuropsychiatric/neurodegenerative and cardiovascular diseases.

Reduced Child-Oriented Face Mirroring Brain Responses in Mothers With Opioid Use Disorder: An Exploratory Study

While the prevalence of opioid use disorder (OUD) among pregnant women has multiplied in the United States in the last decade, buprenorphine treatment (BT) for peripartum women with OUD has been administered to reduce risks of repeated cycles of craving and withdrawal. However, the maternal behavior and bonding in mothers with OUD may be altered as the underlying maternal behavior neurocircuit (MBN) is opioid sensitive. In the regulation of rodent maternal behaviors such as licking and grooming, a series of opioid-sensitive brain regions are functionally connected, including the ventral pallidum (VP). In humans, these brain regions, interact with the supplementary motor area (SMA) to regulate maternal behaviors and are functionally dysregulated by opioids. It is unclear how these brain regions respond to the emotions of their child for mothers receiving BT. In this functional magnetic resonance imaging (fMRI) pilot study in 22 mothers within the first postpartum year, including six mothers receiving BT and 16 non-OUD mothers as a comparison group (CG), we devised a child face mirroring task in fMRI settings to assess maternal responses to pictures of facial expressions of own child and an unknown child in an empathic mirroring condition (Join) and a non-mirroring observation condition (Observe). In each condition, faces of neutral, ambiguous, distressed, and joyful expressions of each child were repeatedly displayed in a random order. The response of SMA during empathic mirroring (Join) vs. non-mirroring (Observe) of own child was reduced among BT/OUD vs. CG. Within MBN, the left VP, critical for parental sensitivity, had a similar deficit. This study outlines potential mechanisms for investigating the risks of deficits in the neural responses to actual maternal sensitivity and parenting behavior in mothers with OUD, and potential targets for interventions that reduce stress and augment maternal behavior and child outcome.

Minding my brain: Fourteen neuroscience-based principles to enhance psychotherapy responsiveness

Intersections between psychotherapy and neurosciences are at its dawn. The quest to understand the neural underpinnings of psychological processes has led several generations of scientists to explore neural correlates between mind, brain, and behavior. Neuroscience methods and research has given psychology new perspectives and insights about the structure and function of complex neural pathways, that underly human functioning (cognition, emotion, motivation, and interpersonal behavior). By translating neuroscientific findings into psychotherapeutic principles of change, it is possible to promote responsiveness towards brain dysfunction that underlies patients' psychological malfunctioning. In psychotherapy, responsiveness is a core aspect of the therapeutic change process, especially to adapt psychological interventions to patients' motivational stages and preferences, coping styles, neurobehavioral modes, and emotional needs. Within a transtheoretical and translational approach, contemporary neuroscientific findings are revised, discussed, and used to attempt to build-on fourteen theoretical brain-based principles that may be applied to psychotherapy. Translating these empirical findings into practical principles, clinical strategies and tasks is expected to enhance psychotherapy responsiveness grounded on a science-based knowledge of brain functioning.

Seeking motivation and reward: roles of dopamine, hippocampus and supramammillo-septal pathway

Reinforcement learning and goal-seeking behavior are thought to be mediated by midbrain dopamine neurons. However, little is known about neural substrates of curiosity and exploratory behavior, which occur in the absence of clear goal or reward. This is despite behavioral scientists having long suggested that curiosity and exploratory behaviors are regulated by an innate drive. We refer to such behavior as information-seeking behavior and propose 1) key neural substrates and 2) the concept of environment prediction error as a framework to understand information-seeking processes. The cognitive aspect of information-seeking behavior, including the perception of salience and uncertainty, involves, in part, the pathways from the posterior hypothalamic supramammillary region to the hippocampal formation. The vigor of such behavior is modulated by the following: supramammillary glutamatergic neurons; their projections to medial septal glutamatergic neurons; and the projections of medial septal glutamatergic neurons to ventral tegmental dopaminergic neurons. Phasic responses of dopaminergic neurons are characterized as signaling potentially important stimuli rather than rewards. This paper describes how novel stimuli and uncertainty trigger seeking motivation and how these neural substrates modulate information-seeking behavior.

Brain morphometric abnormalities and their associations with affective symptoms in males with methamphetamine use disorder during abstinence

BACKGROUND

Methamphetamine (METH) use induces neurotoxic effects in brain structures and affective symptoms that persist during abstinence. However, the brain morphometry of individuals with METH use disorder (MUD) remains unclear, as well as their associations with affective symptoms during abstinence.

METHODS

Forty-eight abstinent males with MUD and 66 age-, sex-, and education-matched healthy controls (HCs) underwent high-resolution T1-weighted magnetic resonance imaging. Cortical thickness, surface area, volume, local gyrification index (LGI), and subcortical volume were obtained with FreeSurfer software. Brain morphometry differences between groups and their associations with affective symptoms and drug abuse history within the males with MUD were examined, with intracranial volume, age, and years of education as covariates.

RESULTS

Compared with the HCs, the individuals with MUD showed a significantly higher LGI in the right cuneus gyrus, left lingual gyrus, bilateral supramarginal gyrus, right inferior parietal gyrus (IPG), and right dorsal anterior cingulate cortex (clusterwise p < 0.05, Monte Carlo-corrected), as well as a smaller volume of the left nucleus accumbens (NAcc) (p < 0.05, FDR-corrected). However, there were no significant group differences in cortical thickness, area or volume. In addition, the LGI in the right IPG was positively associatedwith the severity of depression and anxiety symptoms in MUDs (p < 0.05, FDR-corrected).

CONCLUSION

Brain morphometric abnormalities in abstinent males with MUD were characterized by hypergyrification across multiple mid-posterior brain regions anda smaller volume of the left NAcc.Gyrification of the right IPG may be a potential neural substrate underlying the affective symptoms experienced by MUDs during abstinence.