The role of dopamine in the pathophysiology and treatment of apathy

How does apathy impact exploration-exploitation decision-making in older patients with neurocognitive disorders?

Apathy is a pervasive clinical syndrome in neurocognitive disorders, characterized by a quantitative reduction in goal-directed behaviors. The brain structures involved in the physiopathology of apathy have also been connected to the brain structures involved in probabilistic reward learning in the exploration-exploitation dilemma. This dilemma in question involves the challenge of selecting between a familiar option with a more predictable outcome, and another option whose outcome is uncertain and may yield potentially greater rewards compared to the known option. The aim of this study was to combine experimental procedures and computational modeling to examine whether, in older adults with mild neurocognitive disorders, apathy affects performance in the exploration-exploitation dilemma. Through using a four-armed bandit reinforcement-learning task, we showed that apathetic older adults explored more and performed worse than non-apathetic subjects. Moreover, the mental flexibility assessed by the Trail-making test-B was negatively associated with the percentage of exploration. These results suggest that apathy is characterized by an increased explorative behavior and inefficient decision-making, possibly due to weak mental flexibility to switch toward the exploitation of the more rewarding options. Apathetic participants also took longer to make a choice and failed more often to respond in the allotted time, which could reflect the difficulties in action initiation and selection. In conclusion, the present results suggest that apathy in participants with neurocognitive disorders is associated with specific disturbances in the exploration-exploitation trade-off and sheds light on the disturbances in reward processing in patients with apathy.

Amphetamines Improve the Motivation to Invest Effort in Attention-Deficit/Hyperactivity Disorder

Prevailing frameworks propose that a key feature of attention-deficit/hyperactivity disorder (ADHD) is lower motivation. An important component of motivation is the willingness to engage in cognitively or physically effortful behavior. However, the degree to which effort sensitivity is impaired in ADHD has rarely been tested, and the efficacy of stimulant medication in ameliorating any such impairments is unclear. Here, we tested 20 individuals with ADHD (11 males, 9 females) who were managed with amphetamine-based medication (dexamfetamine, lisdexamfetamine), and 24 controls (8 males, 16 females). Individuals with ADHD were tested over two counterbalanced sessions, ON and OFF their usual amphetamine-based medication. In each session, participants performed an effort-based decision-making task, in which they were required to choose how much cognitive or physical effort they were willing to engage in return for reward. Our results revealed three main findings. First, individuals with ADHD had lower motivation relative to controls to invest effort in both the cognitive and physical domains. Second, amphetamine increased motivation uniformly across both domains. Finally, the net effect of amphetamine treatment was to mostly restore motivation across both domains of effort relative to healthy controls. These data provide clear evidence for a heightened sensitivity to both cognitive and physical effort in ADHD, and reveal the efficacy of amphetamine-based drugs in restoring effort sensitivity to levels similar to controls. These findings confirm the existence of reduced motivational drive in ADHD, and more broadly provide direct causal evidence for a domain-general role of catecholamines in motivating effortful behavior.SIGNIFICANCE STATEMENT A core feature of attention-deficit/hyperactivity disorder (ADHD) is thought to be a heightened aversion to effort. Surprisingly, however, the degree to which effort sensitivity is impaired in ADHD has rarely been tested. More broadly, the relative efficacy of catecholamines in motivating the investment of cognitive and physical effort is unclear. We tested 20 individuals with ADHD ON and OFF amphetamines, and compared their behavior on an effort-based decision-making task to 24 controls. When tested OFF medication, the ADHD group was less cognitively and physically motivated than controls. However, amphetamines led to a comparable increase in motivation across both domains. This demonstrates the efficacy of catecholamines in facilitating domain-general effort, and highlights the broader potential of such drugs to treat disorders of motivation.

Modeling Effort-Based Decision Making: Individual Differences in Schizophrenia and Major Depressive Disorder

BACKGROUND

A critical facet of motivation is effort-based decision making, which refers to the mental processes involved in deciding whether a potential reward is worth the effort. To advance understanding of how individuals with schizophrenia and major depressive disorder utilize cost-benefit information to guide choice behavior, this study aimed to characterize individual differences in the computations associated with effort-based decision making.

METHODS

One hundred forty-five participants (51 with schizophrenia, 43 with depression, and 51 healthy control participants) completed the Effort Expenditure for Rewards Task, with mixed effects modeling conducted to estimate the predictors of decision making. These model-derived, subject-specific coefficients were then clustered using k-means to test for the presence of discrete transdiagnostic subgroups with different profiles of reward, probability, and cost information utilization during effort-based decision making.

RESULTS

An optimal 2-cluster solution was identified, with no significant differences in the distribution of diagnostic groups between clusters. Cluster 1 (n = 76) was characterized by overall lower information utilization during decision making than cluster 2 (n = 61). Participants in this low information utilization cluster were also significantly older and more cognitively impaired, and their utilization of reward, probability, and cost was significantly correlated with clinical amotivation, depressive symptoms, and cognitive functioning.

CONCLUSIONS

Our findings revealed meaningful individual differences among participants with schizophrenia, depression, and healthy control participants in their utilization of cost-benefit information in the context of effortful decision making. These findings may provide insight into different processes associated with aberrant choice behavior and may potentially guide the identification of more individualized treatment targets for effort-based motivation deficits across disorders.

An Update on Apathy in Alzheimer's Disease

Apathy is a complex multi-dimensional syndrome that affects up to 70% of individuals with Alzheimer's disease (AD). Whilst many frameworks to define apathy in AD exist, most include loss of motivation or goal-directed behaviour as the central feature. Apathy is associated with significant impact on persons living with AD and their caregivers and is also associated with accelerated cognitive decline across the AD spectrum. Neuroimaging studies have highlighted a key role of fronto-striatial circuitry including the anterior cingulate cortex (ACC), orbito-frontal cortex (OFC) and associated subcortical structures. Importantly, the presence and severity of apathy strongly correlates with AD stage and neuropathological biomarkers of amyloid and tau pathology. Following from neurochemistry studies demonstrating a central role of biogenic amine neurotransmission in apathy syndrome in AD, recent clinical trial data suggest that apathy symptoms may improve following treatment with agents such as methylphenidate-which may have an important role alongside emerging non-pharmacological treatment strategies. Here, we review the diagnostic criteria, rating scales, prevalence, and risk factors for apathy in AD. The underlying neurobiology, neuropsychology and associated neuroimaging findings are reviewed in detail. Finally, we discuss current treatment approaches and strategies aimed at targeting apathy syndrome in AD, highlighting areas for future research and clinical trials in patient cohorts.

Modulated effectiveness of rehabilitation motivation by reward strategies combined with tDCS in stroke: study protocol for a randomized controlled trial

Background

Stroke survivors often exhibit low motivation for rehabilitation, hindering their ability to effectively complete rehabilitation training task effectively and participate in daily activities actively. Reward strategies have been identified as an effective method for boosting rehabilitation motivation, but their long-term efficacy remains uncertain. Transcranial direct current stimulation (tDCS) has been recognized as a technique that facilitates plastic changes and functional reorganization of cortical areas. Particularly, tDCS can improve the functional connectivity between brain regions associated with goal-directed behavior when applied to the left dorsolateral prefrontal cortex (dlPFC). Combing reward strategies with tDCS (RStDCS) has been shown to motivate healthy individuals to exert more effort in task performance. However, research exploring the combined and sustained effects of these strategies on rehabilitation motivation in stroke survivors is lacking.

Methods and design

Eighty-seven stroke survivors with low motivation and upper extremity dysfunction will be randomized to receive either conventional treatment, RS treatment, or RStDCS treatment. The RStDCS group will receive reward strategies combined with anodal tDCS stimulation of the left dlPFC. The RS group will receive reward strategies combined with sham stimulation. The conventional group will receive conventional treatment combined with sham stimulation. tDCS stimulation is performed over 3 weeks of hospitalization, 20 min/time, five times a week. Reward strategies refers to personalized active exercise programs for patients during hospitalization and at home. Patients can voluntarily choose tasks for active exercise and self-report to the therapist so as to punch a card for points and exchange gifts. The conventional group will receive home rehabilitation instructions prior to discharge. Rehabilitation motivation, measured using RMS. RMS, FMA, FIM, and ICF activity and social engagement scale will be compared at baseline, 3 weeks, 6 weeks, and 3 months post-enrollment to evaluate patients' multifaceted health condition based on the ICF framework.

Discussion

This study integrates knowledge from social cognitive science, economic behavioral science, and other relevant fields. We utilize straightforward and feasible reward strategies, combined with neuromodulation technology, to jointly improve patients' rehabilitation motivation. Behavioral observations and various assessment tools will be used to monitor patients' rehabilitation motivation and multifaceted health condition according to the ICF framework. The aim is to provide a preliminary exploration path for professionals to develop comprehensive strategies for improving patient rehabilitation motivation and facilitating a complete "hospital-home-society" rehabilitation process.

Clinical trial registration

https://www.chictr.org.cn/showproj.aspx?proj=182589, ChiCTR2300069068.

The Possible Role of Apathy on Conflict Monitoring: Preliminary Findings of a Behavioral Study on Severe Acquired Brain Injury Patients Using Flanker Tasks

The diagnosis of apathy, one of the most common behavioral changes after acquired brain injury (ABI), is important for improving clinical understanding and treatment of persons with ABI. The main aim of this study was to determine the possible role of apathy in conflict monitoring, by using choice reaction time tasks. Methods: We examined behavioral responses of conflict monitoring during three different flanker tasks in 10 severe ABI patients with or without diagnosis of apathy (3 M, mean age = 56.60; 3 M, mean age ± SD = 58.60, respectively), and 15 healthy controls (9 M, mean age = 54.46) Reaction times (RTs), accuracy, and global index of performance (GIP) were analyzed for each task. Results: Only apathetic ABI patients showed a significant difference from healthy subjects (p-value ≤ 0.001), while the performance of patients without apathy was not significantly different from that of healthy controls (p-value = 0.351). Healthy participants had higher accuracy in comparison to both ABI patients with (p < 0.001) and without (p-value = 0.038) apathy, whilst slower RTs were shown by ABI patients without apathy in comparison to both healthy subjects (p-value = 0.045) and apathetic ABI patients (p-value = 0.022). Only patients with apathy exhibited a significantly higher number of missing trials (p-value = 0.001). Conclusions: Our results may suggest a potential link between apathy following severe ABI and conflict monitoring processes, even though further investigations with larger sample size are needed.

Diagnostic and Management Strategies for Common Neurobehavioral and Psychiatric Disturbances Among Patients with Cognitive Impairment and the Dementias

Neurobehavioral and neuropsychiatric symptoms are highly prevalent among individuals diagnosed with cognitive impairment or dementia and impact the quality of life for patients and caregivers alike. Diagnosis and management of these conditions (including primarily depression, anxiety, apathy, psychosis, agitation, and aggression) is crucial to optimal patient care outcomes in clinical practice. The present article provides a practical review of diagnostic approaches and management strategies for behavioral and neuropsychiatric disorders arising in patients with cognitive impairment, up to and including dementia.

Role of serotonin in modulation of decision-making in Parkinson's disease

BACKGROUND

Dysfunction of dopaminergic pathways has been considered to play a pivotal role in Parkinson's disease (PD), affecting the processing of emotional and rewarding information, and potentially leading to symptoms of depression or apathy. However, some aspects of motivation in PD might be affected by non-dopaminergic mechanisms.

AIM AND METHOD

The objective of this experimental medicine study was to investigate the contribution of serotonergic modulation via administration of citalopram (20 mg) for 7 days on motivated decision-making in twenty PD patients, measured using several different computerised tasks and clinical questionnaires that probe different aspects of decision-making. Twenty healthy controls were additionally tested without medication to assess any baseline differences between the two groups.

RESULTS

Results indicated that PD patients were overall less motivated than controls on an effort- and reward-based decision-making task. Citalopram increased or decreased willingness to exert effort for reward, depending on whether baseline motivation was high or low, respectively. A task assessing decision-making under risk revealed higher levels of risk aversion for potential losses in PD patients, which neither serotonin nor the patient's regular dopaminergic medication seemed to restore. However, citalopram in PD was associated with more risk-seeking choices for gains, although patients and controls did not differ on this at baseline.

CONCLUSION

The results provide evidence for a role of the serotonergic system in influencing some aspects of motivated decision-making in PD processes.

Apathy, anhedonia and cognitive dysfunction: common symptoms of depression and neurological disorders

Depression is one of the most common mental disorders in neurological practice. Among other symptoms of depression, a symptom complex represented by apathy, anhedonia, and cognitive impairment plays an important role. This review presents the clinical characteristics of the symptoms described above and discusses modern neurochemical and neuroimaging concepts of their pathogenesis. The problem of pathogenetically substantiated therapy of depression with a predominance of apathy, anhedonia and cognitive impairment is discussed. Fundamental and clinical arguments are presented in favor of the high efficacy of vortioxetine in depression with a predominance of apathy, anhedonia, and cognitive impairment. 

Noradrenergic deficits contribute to apathy in Parkinson's disease through the precision of expected outcomes

Apathy is a debilitating feature of many neuropsychiatric diseases, that is typically described as a reduction of goal-directed behaviour. Despite its prevalence and prognostic importance, the mechanisms underlying apathy remain controversial. Degeneration of the locus coeruleus-noradrenaline system is known to contribute to motivational deficits, including apathy. In healthy people, noradrenaline has been implicated in signalling the uncertainty of expectations about the environment. We proposed that noradrenergic deficits contribute to apathy by modulating the relative weighting of prior beliefs about action outcomes. We tested this hypothesis in the clinical context of Parkinson’s disease, given its associations with apathy and noradrenergic dysfunction. Participants with mild-to-moderate Parkinson’s disease (N = 17) completed a randomised double-blind, placebo-controlled, crossover study with 40 mg of the noradrenaline reuptake inhibitor atomoxetine. Prior weighting was inferred from psychophysical analysis of performance in an effort-based visuomotor task, and was confirmed as negatively correlated with apathy. Locus coeruleus integrity was assessed in vivo using magnetisation transfer imaging at ultra-high field 7T. The effect of atomoxetine depended on locus coeruleus integrity: participants with a more degenerate locus coeruleus showed a greater increase in prior weighting on atomoxetine versus placebo. The results indicate a contribution of the noradrenergic system to apathy and potential benefit from noradrenergic treatment of people with Parkinson’s disease, subject to stratification according to locus coeruleus integrity. More broadly, these results reconcile emerging predictive processing accounts of the role of noradrenaline in goal-directed behaviour with the clinical symptom of apathy and its potential pharmacological treatment.

Apathy is a common and harmful consequence of many neuropsychiatric diseases. Its underlying causes are not fully understood, which prevents the development of new treatments. We approach the problem in a new way, modelling human behaviour in terms of the continuously updated interaction between sensory information and brain-based predictions or ‘priors’ about the consequences of our actions. We have previously shown that apathy is related to a loss of precision of these ‘priors’. We proposed that the precision is controlled by noradrenaline (like adrenaline, but made in the brain). We tested whether the noradrenaline-enhancing drug called atomoxetine can restore the priors’ precision in apathetic people. We enrolled participants with Parkinson’s disease, which is associated with both apathy and noradrenaline loss. We used ultra-high field MRI to measure individual differences in the integrity of specialist region called the locus coeruleus–the brain’s source of noradrenaline. We found that the effect of treatment with atomoxetine on prior precision depended on locus coeruleus integrity: Participants with a degenerated locus coeruleus had a more positive change in prior precision. Our results highlight how individual differences in neuroanatomy can predict the potential benefit of noradrenaline treatments in people suffering from apathy.

A qualitative examination of apathy and physical activity in Huntington's and Parkinson's disease

Aim: In Huntington's disease (HD) and Parkinson's disease (PD), apathy is a frequently cited barrier to participation in physical activity. Current diagnostic criteria emphasize dissociable variants of apathy that differentially affect goal-directed behavior. How these dimensions present and affect physical activity in HD and PD is unknown. Methods: Using a qualitative approach, we examined the experience of apathy and its impact on physical activity in 20 people with early-manifest HD or idiopathic PD. Results: Two major themes emerged: the multidimensionality of apathy, including initiation or goal-identification difficulties, and the interplay of apathy and fatigue; and facilitators of physical activity, including routines, safe environments and education. Conclusion: Physical activity interventions tailored to apathy phenotypes may maximize participant engagement.

The Effects of Safinamide Adjunct Therapy on Depression and Apathy in Patients With Parkinson's Disease: Post-hoc Analysis of a Japanese Phase 2/3 Study

Background and Purpose

Neuropsychiatric symptoms in Parkinson's disease (PD) have been shown to significantly affect quality of life (QOL). We investigated the impact of safinamide on depression and apathy when administered as an adjunct to levodopa in Japanese patients with PD.

Methods

This was a post-hoc analysis of data from a phase 2/3 clinical study of safinamide in Japanese patients with PD experiencing wearing-off (JapicCTI-153056; https://www.clinicaltrials.jp/cti-user/trial/ShowDirect.jsp?japicId=JapicCTI-153056). Patients received placebo, safinamide 50 mg, or safinamide 100 mg as an adjunct therapy. The endpoints for this analysis were changes from baseline to Week 24 in the Unified Parkinson's Disease Rating Scale (UPDRS) Part I item 3 (depression) and item 4 (apathy) scores and the Parkinson's Disease Questionnaire (PDQ-39) “emotional well-being” domain score. Subgroup analyses investigated the relationship between neuropsychologic symptoms and improvements in motor fluctuation and assessed which patient populations might be expected to obtain neuropsychologic benefit from safinamide.

Results

Compared with placebo, safinamide (both doses) significantly improved UPDRS Part I item 3 scores in the overall analysis population, and the 100-mg dose improved UPDRS Part I item 4 scores in the population with apathy at baseline. Changes in the PDQ-39 “emotional well-being” score showed numerical, but not significant, dose-related improvements. Notable reductions in depression were associated with a change in daily ON-time ≥1 h, pain during OFF-time at baseline, and female sex.

Conclusions

The results from this post-hoc analysis of the Japanese phase 2/3 study suggest that safinamide could bring benefits to patients with PD who have mild depression, pain during the OFF phase. In addition, safinamide might provide particular benefits for patients with PD who have mild apathy and female.

Value-based cognition and drug dependency

Value-based decision-making is thought to play an important role in drug dependency. Achieving elevated levels of euphoria or ameliorating dysphoria/pain may motivate goal-directed drug consumption in both drug-naïve and long-time users. In other words, drugs become viewed as the preferred means of attaining a desired internal state. The bias towards choosing drugs may affect one's cognition. Observed biases in learning, attention and memory systems within the brain gradually focus one's cognitive functions towards drugs and related cues to the exclusion of other stimuli. In this narrative review, the effects of drug use on learning, attention and memory are discussed with a particular focus on changes across brain-wide functional networks and the subsequent impact on behaviour. These cognitive changes are then incorporated into the cycle of addiction, an established model outlining the transition from casual drug use to chronic dependency. If drug use results in the elevated salience of drugs and their cues, the studies highlighted in this review strongly suggest that this salience biases cognitive systems towards the motivated pursuit of addictive drugs. This bias is observed throughout the cycle of addiction, possibly contributing to the persistent hold that addictive drugs have over the dependent. Taken together, the excessive valuation of drugs as the preferred means of achieving a desired internal state affects more than just decision-making, but also learning, attentional and mnemonic systems. This eventually narrows the focus of one's thoughts towards the pursuit and consumption of addictive drugs.

Heightened effort discounting is a common feature of both apathy and fatigue

Apathy and fatigue have distinct aetiologies, yet can manifest in phenotypically similar ways. In particular, each can give rise to diminished goal-directed behaviour, which is often cited as a key characteristic of both traits. An important issue therefore is whether currently available approaches are capable of distinguishing between them. Here, we examined the relationship between commonly administered inventories of apathy and fatigue, and a measure of goal-directed activity that assesses the motivation to engage in effortful behaviour. 103 healthy adults completed self-report inventories on apathy (the Dimensional Apathy Scale), and fatigue (the Multidimensional Fatigue Inventory, and/or Modified Fatigue Impact Scale). In addition, all participants performed an effort discounting task, in which they made choices about their willingness to engage in physically effortful activity. Importantly, self-report ratings of apathy and fatigue were strongly correlated, suggesting that these inventories were insensitive to the fundamental differences between the two traits. Furthermore, greater effort discounting was strongly associated with higher ratings across all inventories, suggesting that a common feature of both traits is a lower motivation to engage in effortful behaviour. These results have significant implications for the assessment of both apathy and fatigue, particularly in clinical groups in which they commonly co-exist.

The neural basis of effort valuation: A meta-analysis of functional magnetic resonance imaging studies

Choosing how much effort to expend is critical for everyday decisions. While several neuroimaging studies have examined effort-based decision-making, results have been highly heterogeneous, leaving unclear which brain regions process effort-related costs and integrate them with rewards. We conducted two meta-analyses of functional magnetic resonance imaging data to examine consistent neural correlates of effort demands (23 studies, 15 maps, 549 participants) and net value (15 studies, 11 maps, 428 participants). The pre-supplementary motor area (pre-SMA) scaled positively with pure effort demand, whereas the ventromedial prefrontal cortex (vmPFC) showed the opposite effect. Moreover, regions that have been previously implicated in value integration in other cost domains, such as the vmPFC and ventral striatum, were consistently involved in signaling net value. The opposite response patterns of the pre-SMA and vmPFC imply that they are differentially involved in the representation of effort costs and value integration. These findings provide conclusive evidence that the vmPFC is a central node for net value computation and reveal potential brain targets to treat motivation-related disorders.

Treatment of the behavioral variant of frontotemporal dementia: a narrative review

Frontotemporal dementia (FTD) is a progressive neurodegenerative disorder accompanied by behavioral and personality changes and/or language deterioration. Its behavioral variant (bvFTD) is the main clinical presentation.

Objective

This study aims to investigate the treatment alternatives for bvFTD available so far.

Methods

We conducted a narrative review of bvFTD treatment options. We used PubMed and Lilacs databases with the terms "frontotemporal dementia" or "behavioral variant frontotemporal dementia" combined with "treatment," "pharmacological treatment," or "disease-modifying drugs."

Results

The articles retrieved and selected in the research pointed out that there is no specific treatment approved for bvFTD so far. The current proposals are limited to handle the cardinal behavioral symptoms of the disorder. Disease-modifying drugs are under development and may be promising, especially in the monogenic presentations of FTD.

Conclusions

There are numerous approaches to treat the core symptoms of bvFTD, most of them based on low-quality research. To date, there are no drugs with a disease-specific therapeutic recommendation for bvFTD. Treatments are often investigated guided by primary psychiatric disorders with similar symptoms and should be chosen by the predominant symptom profile.

Apathy: Neurobiology, Assessment and Treatment

Apathy is a highly prevalent, disabling and treatment resistant syndrome. It is defined as a quantitative reduction of goal- directed activity in comparison to the patient’s previous level of in multiple dimensions including behavior/cognition, emotion and social interaction. It has been described in major depressive disorder, Alzheimer’s disease, frontotemporal dementia, Parkinson’s Disease, cerebrovascular disease, and vascular dementia, among others. This review will address the neuropsychology and associated neurobiological underpinnings of apathy in the above conditions, identify specific methods to assess apathy clinically, and review the literature on managing apathy across these various disorders.

Apathy in small vessel cerebrovascular disease is associated with deficits in effort-based decision making

Patients with small vessel cerebrovascular disease frequently suffer from apathy, a debilitating neuropsychiatric syndrome, the underlying mechanisms of which remain to be established. Here we investigated the hypothesis that apathy is associated with disrupted decision making in effort-based decision making, and that these alterations are associated with abnormalities in the white matter network connecting brain regions that underpin such decisions. Eighty-two patients with MRI evidence of small vessel disease were assessed using a behavioural paradigm as well as diffusion weighted MRI. The decision-making task involved accepting or rejecting monetary rewards in return for performing different levels of physical effort (hand grip force). Choice data and reaction times were integrated into a drift diffusion model that framed decisions to accept or reject offers as stochastic processes approaching a decision boundary with a particular drift rate. Tract-based spatial statistics were used to assess the relationship between white matter tract integrity and apathy, while accounting for depression. Overall, patients with apathy accepted significantly fewer offers on this decision-making task. Notably, while apathetic patients were less responsive to low rewards, they were also significantly averse to investing in high effort. Significant reductions in white matter integrity were observed to be specifically related to apathy, but not to depression. These included pathways connecting brain regions previously implicated in effort-based decision making in healthy people. The drift rate to decision parameter was significantly associated with both apathy and altered white matter tracts, suggesting that both brain and behavioural changes in apathy are associated with this single parameter. On the other hand, depression was associated with an increase in the decision boundary, consistent with an increase in the amount of evidence required prior to making a decision. These findings demonstrate altered effort-based decision making for reward in apathy, and also highlight dissociable mechanisms underlying apathy and depression in small vessel disease. They provide clear potential brain and behavioural targets for future therapeutic interventions, as well as modelling parameters that can be used to measure the effects of treatment at the behavioural level.

Saffron Extract-Induced Improvement of Depressive-Like Behavior in Mice Is Associated with Modulation of Monoaminergic Neurotransmission

Depressive disorders represent a major public health concern and display a continuously rising prevalence. Importantly, a large proportion of patients develops aversive side effects and/or does not respond properly to conventional antidepressants. These issues highlight the need to identify further therapeutic strategies, including nutritional approaches using natural plant extracts with known beneficial impacts on health. In that context, growing evidence suggests that saffron could be a particularly promising candidate. This preclinical study aimed therefore to test its antidepressant-like properties in mice and to decipher the underlying mechanisms by focusing on monoaminergic neurotransmission, due to its strong implication in mood disorders. For this purpose, the behavioral and neurobiochemical impact of a saffron extract, Safr’Inside™ (6.5 mg/kg per os) was measured in naïve mice. Saffron extract reduced depressive-like behavior in the forced swim test. This behavioral improvement was associated with neurobiological modifications, particularly changes in serotonergic and dopaminergic neurotransmission, suggesting that Safr’Inside™ may share common targets with conventional pharmacological antidepressants. This study provides useful information on the therapeutic relevance of nutritional interventions with saffron extracts to improve management of mood disorders.

Apathy after stroke: Diagnosis, mechanisms, consequences, and treatment

Apathy is a reduction in goal-directed activity in the cognitive, behavioral, emotional, or social domains of a patient’s life and occurs in one out of three patients after stroke. Despite this, apathy is clinically under-recognized and poorly understood. This overview provides a contemporary introduction to apathy in stroke for researchers and practitioners, covering topics including diagnosis, neurobiological mechanisms, associated consequences, and potential treatments for apathy. Apathy is often misdiagnosed as other post-stroke conditions such as depression. Accurate differential diagnosis of apathy, which manifests as reductions in initiative, and depression, which manifests as negative emotionality, is important as it informs prognosis. Research on the neurobiology of apathy suggests that there are few consistent associations between stroke lesion location and the development of apathy. These may be resolved by adopting a network neuroscience approach, which models apathy as a pathology arising from structural or functional damage to brain networks underlying motivated behavior. Importantly, networks can be affected by physiological changes related to stroke, including the acute infarct but also diaschisis and neurodegeneration. Aside from neurobiological changes, apathy is also associated with other negative outcome measures such as functional disability, cognitive impairment, and emotional distress, suggesting that apathy is indicative of a worse prognosis following stroke. Unfortunately, high-quality trials aimed at treating apathy are scarce. Antidepressants may have limited effects on apathy. Acetylcholine and dopamine pharmacotherapy, behavioral interventions, and transcranial magnetic stimulation may be more promising avenues for treatment.

Prenatal Alcohol Exposure in Rats Diminishes Postnatal Cxcl16 Chemokine Ligand Brain Expression

Maternal ethanol consumption during pregnancy is one of the main causes of Neurodevelopmental disorders (NDD). Prenatal alcohol exposure (PAE) produces several adverse manifestations. Even low or moderate intake has been associated with long-lasting behavioral and cognitive impairment in offspring. In this study we examined the gene expression profile in the rat nucleus accumbens using microarrays, comparing animals exposed prenatally to ethanol and controls. Microarray gene expression showed an overall downward regulatory effect of PAE. Gene cluster analysis reveals that the gene groups most affected are related to transcription regulation, transcription factors and homeobox genes. We focus on the expression of the C-X-C motif chemokine ligand 16 (Cxcl16) which was differentially expressed. There is a significant reduction in the expression of this chemokine throughout the brain under PAE conditions, evidenced here by quantitative polymerase chain reaction qPCR and immunohistochemistry. Chemokines are involved in neuroprotection and implicated in alcohol-induced brain damage and neuroinflammation in the developing central nervous system (CNS), therefore, the significance of the overall decrease in Cxcl16 expression in the brain as a consequence of PAE may reflect a reduced ability in neuroprotection against subsequent conditions, such as excitotoxic damage, inflammatory processes or even hypoxic-ischemic insult.

Dissociable Motivational Deficits in Pre-manifest Huntington's Disease

Motivation is characterized by a willingness to overcome both cognitive and physical effort costs. Impairments in motivation are common in striatal disorders, such as Huntington’s disease (HD), but whether these impairments are isolated to particular domains of behavior is controversial. We ask whether HD differentially affects the willingness of individuals to overcome cognitive versus physical effort. We tested 20 individuals with pre-manifest HD and compared their behavior to 20 controls. Across separate trials, participants made choices about how much cognitive or physical effort they were willing to invest for reward. Our key results were that individuals with pre-manifest HD were less willing than controls to invest cognitive effort but were no different in their overall preference for physical effort. These results cannot be explained by group differences in neuropsychological or psychiatric profiles. This dissociation of cognitive- and physical-effort-based decisions provides important evidence for separable, domain-specific mechanisms of motivation.

We examine cognitive and physical effort discounting in pre-manifest HD

Individuals with pre-manifest HD are less cognitively motivated than controls

There are no differences in physical motivation between the two groups

This dissociation is not confounded by neuropsychological or psychiatric factors

Neuroanatomical Abnormalities in Older Depressed Adults With Apathy: A Systematic Review

OBJECTIVE

Apathy is a common phenomenon in late-life depression and is associated with poor outcomes. Apathy is often unrecognized in older depressed adults, and efficacious treatment options are lacking. This review provides a systematic review of the neuroanatomical abnormalities associated with apathy in late-life depression. In addition, the review summarizes the neuroimaging findings from studies of neurodegenerative and focal brain injury conditions that frequently present with apathy. The goal is to elucidate cerebral network abnormalities that give rise to apathy in older adults with mood disturbances and to inform future treatment targets.

METHOD

Systematic literature review.

RESULTS

The few studies that have directly examined the neuroanatomical abnormalities of apathy in late-life depression suggest disturbances in the anterior cingulate cortex, insula, orbital and dorsal prefrontal cortex, striatum, and limbic structures (ie, amygdala, thalamus, and hippocampus). Studies examining the neuroanatomical correlates of apathy in other aging populations are consistent with the pattern observed in late-life depression.

CONCLUSIONS

Apathy in late-life depression appears to be accompanied by neuroanatomical abnormalities in the salience and reward networks. These network findings are consistent with that observed in individuals presenting with apathy in other aging-related conditions. These findings may inform future treatments that target apathy.

Network neuroscience of apathy in cerebrovascular disease

Apathy is a reduction in motivated goal-directed behavior (GDB) that is prevalent in cerebrovascular disease, providing an important opportunity to study the mechanistic underpinnings of motivation in humans. Focal lesions, such as those seen in stroke, have been crucial in developing models of brain regions underlying motivated behavior, while studies of cerebral small vessel disease (SVD) have helped define the connections between brain regions supporting such behavior. However, current lesion-based models cannot fully explain the neurobiology of apathy in stroke and SVD. To address this, we propose a network-based model which conceptualizes apathy as the result of damage to GDB-related networks. A review of the current evidence suggests that cerebrovascular disease-related pathology can lead to network changes outside of initially damaged territories, which may propagate to regions that share structural or functional connections. The presentation and longitudinal trajectory of apathy in stroke and SVD may be the result of these network changes. Distinct subnetworks might support cognitive components of GDB, the disruption of which results in specific symptoms of apathy. This network-based model of apathy may open new approaches for investigating its underlying neurobiology, and presents novel opportunities for its diagnosis and treatment.

Bupropion for the Treatment of Apathy in Alzheimer Disease: A Randomized Clinical Trial

IMPORTANCE

Apathy is a frequent neuropsychiatric symptom in dementia of Alzheimer type and negatively affects the disease course and patients' and caregivers' quality of life. Effective treatment options are needed.

OBJECTIVE

To examine the efficacy and safety of the dopamine and noradrenaline reuptake inhibitor bupropion in the treatment of apathy in patients with dementia of Alzheimer type.

DESIGN, SETTING, AND PARTICIPANTS

This 12-week, multicenter, double-blind, placebo-controlled, randomized clinical trial was conducted in a psychiatric and neurological outpatient setting between July 2010 and July 2014 in Germany. Patients with mild-to-moderate dementia of Alzheimer type and clinically relevant apathy were included. Patients with additional clinically relevant depressed mood were excluded. Data analyses were performed between August 2018 and August 2019.

INTERVENTIONS

Patients received either bupropion or placebo (150 mg for 4 weeks plus 300 mg for 8 weeks). In case of intolerability of 300 mg, patients continued to receive 150 mg throughout the study.

MAIN OUTCOMES AND MEASURES

Change on the Apathy Evaluation Scale-Clinician Version (AES-C) (score range, 18-72 points) between baseline and week 12 was the primary outcome parameter. Secondary outcome parameters included measures of neuropsychiatric symptoms, cognition, activities of daily living, and quality of life. Outcome measures were assessed at baseline and at 4, 8, and 12 weeks.

RESULTS

A total of 108 patients (mean [SD] age, 74.8 [5.9] years; 67 men [62%]) were included in the intention-to-treat analysis, with 54 randomized to receive bupropion and 54 randomized to receive placebo. The baseline AES-C score was comparable between the bupropion group and the placebo group (mean [SD], 52.2 [8.7] vs 50.4 [8.2]). After controlling for the baseline AES-C score, site, and comedication with donepezil or galantamine, the mean change in the AES-C score between the bupropion and placebo groups was not statistically significant (mean change, 2.22; 95% CI, -0.47 to 4.91; P = .11). Results on secondary outcomes showed statistically significant differences between bupropion and placebo in terms of total neuropsychiatric symptoms (mean change, 5.52; 95% CI, 2.00 to 9.04; P = .003) and health-related quality of life (uncorrected for multiple comparisons; mean change, -1.66; 95% CI, -3.01 to -0.31; P = .02) with greater improvement in the placebo group. No statistically significant changes between groups were found for activities of daily living (mean change, -2.92; 95% CI, -5.89 to 0.06; P = .05) and cognition (mean change, -0.27; 95% CI, -3.26 to 2.73; P = .86). The numbers of adverse events (bupropion group, 39 patients [72.2%]; placebo group, 33 patients [61.1%]) and serious adverse events (bupropion group, 5 patients [9.3%]; placebo group, 2 patients [3.7%]) were comparable between groups.

CONCLUSIONS AND RELEVANCE

Although it is safe, bupropion was not superior to placebo for the treatment of apathy in patients with dementia of Alzheimer type in the absence of clinically relevant depressed mood.

TRIAL REGISTRATION

EU Clinical Trials Register Identifier: 2007-005352-17.

Prodopaminergic Drugs for Treating the Negative Symptoms of Schizophrenia: Systematic Review and Meta-analysis of Randomized Controlled Trials

BACKGROUND

The negative symptoms of schizophrenia pose a heavy burden on patients and relatives and represent an unmet therapeutic need. The observed association of negative symptoms with impaired reward system function has stimulated research on prodopaminergic agents as potential adjunctive treatments.

METHODS

We conducted a systematic review and meta-analysis of published randomized controlled trials of amphetamine, methylphenidate, modafinil, armodafinil, lisdexamphetamine, L-dopa, levodopa, bromocriptine, cabergoline, quinagolide, lisuride, pergolide, apomorphine, ropinirole, pramipexole, piribedil, and rotigotine augmentation in schizophrenia and schizoaffective disorder.Medline, EMBASE, and several other databases as well as trial registries were searched for placebo-controlled trials.

RESULTS

Ten randomized controlled trials were included in the meta-analysis, 6 trials on modafinil, 2 on armodafinil, 1 on L-dopa, and 1 on pramipexole. Overall, prodopaminergic agents did not significantly reduce negative symptoms. Restricting the analysis to studies requiring a minimum threshold for negative symptom severity, modafinil/armodafinil showed a significant but small effect on negative symptoms. A subset of studies allowed for calculating specific effects for the negative symptom dimensions diminished expression and amotivation, but no significant effect was found. Prodopaminergic agents did not increase positive symptom scores.

CONCLUSIONS

The currently available evidence does not allow for formulating recommendations for the use of prodopaminergic agents for the treatment of negative symptoms. Nevertheless, the observed improvement in studies defining a minimum threshold for negative symptom severity in the absence of an increase in positive symptoms clearly supports further research on these agents.

A transnosographic approach of negative symptoms pathophysiology in schizophrenia and depressive disorders

BACKGROUND

Negative Symptoms (blunted affect, alogia, anhedonia, avolition and asociality) are observed in schizophrenia but also in depressive disorders.

OBJECTIVE

To gather cognitive, neuroanatomical, neurofunctional and neurobiological knowledge of negative symptoms in studies on schizophrenia, depressive disorder, and transnosographic studies.

RESULTS

Blunted affect in schizophrenia is characterized by amygdala hyperactivation and frontal hypoactivation, also found in depressive disorder. Mirror neurons, may be related to blunted affect in schizophrenia. Alogia may be related to cognitive dysfunction and basal ganglia area impairments in schizophrenia. Data surrounding alogia in depressive disorder is scarce; wider speech deficits are often studied instead. Consummatory Anhedonia may be less affected than Anticipatory Anhedonia in schizophrenia. Anhedonia is associated with reward impairments and altered striatal functions in both diagnostics. Amotivation is associated with Corticostriatal Hypoactivation in both disorders. Anhedonia and amotivation are transnosographically associated with dopamine dysregulation. Asociality may be related to oxytocin.

CONCLUSION

Pathophysiological hypotheses are specific to each dimension of negative symptoms and overlap across diagnostic boundaries, possibly underpinning the observed clinical continuum.

Cell adhesion molecule close homolog of L1 binds to the dopamine receptor D2 and inhibits the internalization of its short isoform

Cell adhesion molecule close homolog of L1 (CHL1) and the dopamine receptor D2 (DRD2) are associated with psychiatric and mental disorders. We here show that DRD2 interacts with CHL1 in mouse brain, as evidenced by co-immunostaining, proximity ligation assay, co-immunoprecipitation, and pull-down assay with recombinant extracellular CHL1 domain fused to Fc (CHL1-Fc). Direct binding of CHL1-Fc to the first extracellular loop of DRD2 was shown by ELISA. Using HEK cells transfected to co-express CHL1 and the short (DRD2-S) or long (DRD2-L) DRD2 isoforms, co-localization of CHL1 and both isoforms was observed by immunostaining and proximity ligation assay. Moreover, CHL1 inhibited agonist-triggered internalization of DRD2-S. Proximity ligation assay showed close interaction between CHL1 and DRD2 in neurons expressing dopamine- and cAMP-regulated phosphoprotein of 32 kDa (DARPP32) or tyrosine hydroxylase (TH) in tissue sections of adult mouse striatum. In cultures of striatum or ventral midbrain, CHL1 was also closely associated with DRD2 in DARPP32- or TH-immunopositive cells, respectively. In the dorsal striatum of CHL1-deficient mice, lower levels of DRD2 and phosphorylated TH were observed, when compared to wild-type littermates. In the ventral striatum of CHL1-deficient mice, levels of phosphorylated DARPP32 were reduced. We propose that CHL1 regulates DRD2-dependent presynaptic and postsynaptic functions.

Effects of gender on cognitive and behavioral manifestations in multiple system atrophy

Gender differences have been described in several neurodegenerative disorders, such as Alzheimer's disease and Parkinson's disease. The effects of gender on cognitive and behavioral manifestations in multiple system atrophy and the changes of cognitive functions over time according to gender have not been investigated so far. Fifty-five patients with a diagnosis of multiple system atrophy underwent a comprehensive neuropsychological and neuropsychiatric battery at baseline and 26 of them could be re-evaluated at 1-year follow-up. At baseline women with multiple system atrophy had poorer global cognitive state and visuo-spatial abilities, and a higher prevalence of depression and apathy than males. At follow-up, female patients deteriorated more than males on attention abilities and motor functions, and had a higher prevalence of depression than men. Executive functions and visuo-spatial abilities significantly worsened over time in both groups. Mild Cognitive Impairment single domain was significantly more frequent in females than males. Cognitive and behavioral differences between genders in multiple system atrophy involve global cognition, planning, attention, visual-perceptive skills, and depression, with female patients more compromised than males. Female patients deteriorated more than men over time as for motor functions and attention. Further longitudinal studies are deserved to confirm gender differences in progression of cognitive and behavioral features of multiple system atrophy.

Tetrahydrobiopterin administration facilitates amphetamine-induced dopamine release and motivation in mice

Dopamine (DA) is a critical neurotransmitter involved in motivational processes. Tetrahydrobiopterin (BH4) is an essential cofactor for tyrosine hydroxylase, the rate-limiting enzyme in DA synthesis. Decreases in BH4 levels are observed in several DA-related neuropsychiatric diseases involving impairment in motivation. Yet, whether BH4 could be used to treat motivational deficits has not been comprehensively investigated. To investigate the effects of exogenous BH4 administration on the dopaminergic system and related behaviors, we acutely injected mice with BH4 (50 mg/kg). Passage of BH4 through the blood brain barrier and accumulation in brain was measured using the in situ brain perfusion technique. DA release was then recorded using in-vivo micro-dialysis and motivation was evaluated through operant conditioning paradigms in basal condition and after an amphetamine (AMPH) injection. First, we showed that BH4 crosses the blood-brain barrier and that an acute peripheral injection of BH4 is sufficient to increase the concentrations of biopterins in the brain, without affecting BH4- and DA-related protein expression. Second, we report that this increase in BH4 enhanced AMPH-stimulated DA release in the nucleus accumbens. Finally, we found that BH4-induced DA release led to improved performance of a motivational task. Altogether, these findings suggest that BH4, through its action on the dopaminergic tone, could be used as a motivational enhancer.

Dopamine restores cognitive motivation in Parkinson's disease

Disorders of motivation, such as apathy, are common in Parkinson's disease, and a key feature of such disorders is a greater aversion to effort. In humans, the experience of cognitive effort is ubiquitous, and cognitive apathy has traditionally been considered distinct and separable from other subtypes. Surprisingly, however, the neurobiology of cognitive motivation is poorly understood. In particular, although dopamine has a well-characterized role in incentivizing physically effortful behaviour, a critical, unresolved issue is whether its facilitatory role generalizes to other domains. Here, we asked how dopamine modulates the willingness of patients with Parkinson's disease to invest cognitive effort in return for reward. We tested 20 patients with idiopathic Parkinson's disease across two counterbalanced sessions-ON and OFF their usual dopaminergic medication-and compared their performance to 20 healthy age-matched controls. We applied a novel task in which we manipulated cognitive effort as the number of rapid serial visual presentation streams to which participants had to attend. After training participants to ceiling performance, we then asked them to choose between a low-effort/low-reward baseline option, and a higher-effort/higher-reward offer. Computational models of choice behaviour revealed four key results. First, patients OFF medication were significantly less cognitively motivated than controls, as manifest by steeper cognitive effort discounting functions in the former group. Second, dopaminergic therapy improved this deficit, such that choices in patients ON medication were indistinguishable from controls. Third, differences in motivation were also accompanied by independent changes in the stochasticity of individuals' decisions, such that dopamine reduced the variability in choice behaviour. Finally, choices on our task correlated uniquely with the subscale of the Dimensional Apathy Scale that specifically indexes cognitive motivation, which suggests a close relationship between our laboratory measure of cognitive effort discounting and subjective reports of day-to-day cognitive apathy. Importantly, participants' choices were not confounded by temporal discounting, probability discounting, physical demand, or varying task performance. These results are the first to reveal the central role of dopamine in overcoming cognitive effort costs. They provide an insight into the computational mechanisms underlying cognitive apathy in Parkinson's disease, and demonstrate its amenability to dopaminergic therapy. More broadly, they offer important empirical support for prominent frameworks proposing a domain-general role for dopamine in value-based decision-making, and provide a critical link between dopamine and multidimensional theories of apathy.

Reward sensitivity predicts dopaminergic response in spatial neglect

It has recently been revealed that spatial neglect can be modulated by motivational factors including anticipated monetary reward. A number of dopaminergic agents have been evaluated as treatments for neglect, but the results have been mixed, with no clear anatomical or cognitive predictors of dopaminergic responsiveness. Given that the effects of incentive motivation are mediated by dopaminergic pathways that are variably damaged in stroke, we tested the hypothesis that the modulatory influences of reward and dopaminergic drugs on neglect are themselves related. We employed a single-dose, double-blind, crossover design to compare the effects of Co-careldopa and placebo on a modified visual cancellation task in patients with neglect secondary to right hemisphere stroke. Whilst confirming that reward improved visual search in this group, we showed that dopaminergic stimulation only enhances visual search in the absence of reward. When patients were divided into REWARD-RESPONDERs and REWARD-NON-RESPONDERs, we found an interaction, such that only REWARD-NON-RESPONDERs showed a positive response to reward after receiving Co-careldopa, whereas REWARD-RESPONDERs were not influenced by drug. At a neuroanatomical level, responsiveness to incentive motivation was most associated with intact dorsal striatum. These findings suggest that dopaminergic modulation of neglect follows an 'inverted U' function, is dependent on integrity of the reward system, and can be measured as a behavioural response to anticipated reward.

Unmet Needs in Pharmacological Treatment of Apathy in Alzheimer's Disease: A Systematic Review

Background: Apathy is one of the most prevalent neuropsychiatric symptoms encountered in Alzheimer’s disease (AD) and may be an early sign in the development of dementia persisting over the disease course. It has been associated with poor disease outcome, impaired daily functioning, and significant caregiver distress. Early diagnosis and timely treatment of apathy in AD are of great importance. However, approved agents for apathy are still missing.

Methods: Within this context, we conducted an extensive electronic search in the databases included in the National Library of Medicine, PsychInfo, and Google Scholar for studies that have investigated the effect of pharmacological treatments in apathy in AD. There were no limitations regarding study design and all care settings were considered for inclusion. Structured measures for level of evidence and study quality were employed to evaluate the results.

Results: A total of 1,607 records were identified; 1,483 records remained after the removal of duplicates and were screened; 166 full-text articles were selected and assessed for eligibility and a remaining 90 unique studies and relevant reviews were included in the qualitative synthesis. Acetylcholinesterase inhibitors, gingko biloba, and methylphenidate were found to be successful in reducing apathy in patients with AD. Methodological heterogeneity in the studies and the small amount of studies where apathy was the primary outcome are limiting factors to assess for group effects.

Conclusions: Pharmacological treatment of apathy in AD is an underexplored field. Standardized and systematic efforts are needed to establish a possible treatment benefit. Elucidating the pathophysiology of apathy and its components or subtypes will inform disease models and mechanistic drug studies that can quantify a benefit from specific agents for specific AD groups.

Updating Apathy: Using Research Domain Criteria to Inform Clinical Assessment and Diagnosis of Disorders of Motivation

Clinical observations regarding apathy and motivation derived from many psychiatric and neurological conditions have generated divergent descriptions of apathy-related syndromes. Stimulated by complex cases presenting with prominent apathy, uses of the term "apathy" and "related phenomena" in the Diagnostic and Statistical Manual of Mental Disorders, diagnostic proposals for apathy as a syndrome and disorder of motivation, Research Domain Criteria (RDoC) systems governing motivational processes, and their clinical intersections are reviewed. Clinical apathy and associated dysfunctions can be addressed using constructs suggested by the RDoC domain of Positive Valence Systems, including approach motivation and component processes of reward valuation, effort valuation/willingness to work, expectancy/reward prediction error, and responses to reward and reward learning. Although apathy syndromes have been validated, defining potentially distinct disorders of motivation (not simply subordinated to mood, psychotic, cognitive, or substance use disorders) will require additional research to better delineate etiology and pathogenesis, predictive validators, reliable diagnostic methods, treatments, and demonstrations of use for these diagnostic proposals.

The Roles of Apathy and Depression in Predicting Alzheimer Disease: A Longitudinal Analysis in Older Adults With Mild Cognitive Impairment

OBJECTIVE

Apathy and depression have each been associated with an increased risk of conversion from mild cognitive impairment (MCI) to Alzheimer disease (AD).These symptoms often co-occur and the contribution of each to risk of AD is not clear.

METHODS

National Alzheimer's Coordinating Center participants diagnosed with MCI at baseline and followed until development of AD or loss to follow-up (n = 4,932) were included. The risks of developing AD in MCI patients with neuropsychiatric symptoms (NPS) (apathy only, depression only, or both) were compared to that in those without NPS in a multivariate Cox regression survival analysis adjusting for baseline cognitive impairment, years of smoking, antidepressant use, and AD medication use.

RESULTS

Thirty-seven percent (N = 1713) of MCI patients developed AD (median follow-up 23 months). MCI patients with both apathy and depression had the greatest risk (hazard ratio [HR] = 1.37; 95% confidence interval [CI]: 1.17-1.61; p < 0.0001; Wald χ2 = 14.70; df = 1). Those with apathy only also had a greater risk (HR = 1.24; 95% CI: 1.05-1.47; p = 0.01; Wald χ2 = 6.22; df = 1), but not those with depression only (HR = 1.08; 95% CI: 0.95-1.22; p=0.25; Wald χ2 = 1.30; df = 1). Post-hoc analyses suggested depression may exacerbate cognitive decline in MCI patients with apathy (odds ratio = 0.70; 95% CI 0.52-0.95; p = 0.02; Wald χ2 = 5.28; df = 1), compared to those without apathy.

CONCLUSION

MCI patients with apathy alone or both apathy and depression are at a greater risk of developing AD compared to those with no NPS. Interventions targeting apathy and depression may reduce risk of AD.

Dopaminergic Genes Polymorphisms and Prefrontal Cortex Efficiency Among Obese People - Whether Gender is a Differentiating Factor?

BACKGROUND

Obesity is a chronic condition associated with poorer cognitive functioning. Wisconsin Card Sorting Test (WCST) is a useful tool for evaluating executive functions. In this study, we assessed the association between dopaminergic gene polymorphisms: DAT1 (SLC6A3), COMTVal158Met, DRD4 (48-bp variable number of tandem repeats - VNTR) and WCST parameters to investigate the functions of the frontal lobes in obese individuals.

OBJECTIVE

To find the significant correlations between polymorphisms of DAT1, COMTVal158Met, DRD4 and executive functions in obese subjects.

METHODS

The analysis of the frequency of individual alleles was performed in 248 obese patients (179 women, 69 men). Evaluation of the prefrontal cortex function (operating memory and executive functions) was measured with the Wisconsin Card Sorting Test (WCST). Separate analyzes were performed in age subgroups to determine different activities and regulation of genes in younger and older participants.

RESULTS

Scores of WCST parameters were different in the subgroups of women and men and in the age subgroups. Regarding the COMT gene, patients with A/A and G/A polymorphisms showed significantly better WCST results in WCST_P, WCST_CC and WCST_1st. Regarding DAT1 men with L/L and L/S made less non-perseverative errors, which was statistically significant. In DRD4, significantly better WCST_1st results were found only in older women with S allele.

CONCLUSION

Obtained results indicate the involvement of dopaminergic transmission in the regulation of prefrontal cortex function. Data analysis indicates that prefrontal cortex function may ensue, from different elements such as genetic factors, metabolic aspects of obesity, and hormonal activity (estrogen).

Neural correlates of effort-based valuation with prospective choices

How is effort integrated in value-based decision-making? Animal models and human neuroimaging studies primarily linked the anterior cingulate cortex (ACC) and ventral striatum (VS) to the integration of effort in valuation. Other studies demonstrated the role of these regions in invigoration to effort demands, thus it is hard to separate the neural activity linked to anticipation and subjective valuation from actual performance. Here, we studied the neural basis of effort valuation separated from performance. We scanned forty participants with fMRI, while they were asked to accept or reject monetary gambles that could be resolved with future performance of a familiar grip force effort challenge or a fixed risk prospect. Participants' willingness to accept prospective gambles reflected discounting of values by physical effort and risk. Choice-locked neural activation in contralateral primary sensory cortex and ventromedial prefrontal cortex (vmPFC) tracked the magnitude of prospective effort the participants faced, independent of choice time and monetary stakes. Estimates of subjective value discounted by effort were found to be tracked by the activation of a network of regions common to valuation under risk and delay, including vmPFC, VS and sensorimotor cortex. Together, our findings show separate neural mechanisms underlying prospective effort and actual effort performance.

Ventral midbrain astrocytes display unique physiological features and sensitivity to dopamine D2 receptor signaling

Astrocytes are ubiquitous CNS cells that support tissue homeostasis through ion buffering, neurotransmitter recycling, and regulation of CNS vasculature. Yet, despite the essential functional roles they fill, very little is known about the physiology of astrocytes in the ventral midbrain, a region that houses dopamine-releasing neurons and is critical for reward learning and motivated behaviors. Here, using a combination of whole-transcriptome sequencing, histology, slice electrophysiology, and calcium imaging, we performed the first functional and molecular profiling of ventral midbrain astrocytes and observed numerous differences between these cells and their telencephalic counterparts, both in their gene expression profile and in their physiological properties. Ventral midbrain astrocytes have very low membrane resistance and inward-rectifying potassium channel-mediated current, and are extensively coupled to surrounding oligodendrocytes through gap junctions. They exhibit calcium responses to glutamate but are relatively insensitive to norepinephrine. In addition, their calcium activity can be dynamically modulated by dopamine D2 receptor signaling. Taken together, these data indicate that ventral midbrain astrocytes are physiologically distinct from astrocytes in cortex and hippocampus. This work provides new insights into the extent of functional astrocyte heterogeneity within the adult brain and establishes the foundation for examining the impact of regional astrocyte differences on dopamine neuron function and susceptibility to degeneration.

Synaptic Connectivity in Medium Spiny Neurons of the Nucleus Accumbens: A Sex-Dependent Mechanism Underlying Apathy in the HIV-1 Transgenic Rat

Frontal-subcortical circuit dysfunction is commonly associated with apathy, a neuropsychiatric sequelae of human immunodeficiency virus type-1 (HIV-1). Behavioral and neurochemical indices of apathy in the nucleus accumbens (NAc), a key brain region involved in frontal-subcortical circuitry, are influenced by the factor of biological sex. Despite evidence of sex differences in HIV-1, the effect of biological sex on medium spiny neurons (MSNs), which are central integrators of frontal-subcortical input, has not been systematically evaluated. In the present study, a DiOlistic labeling technique was used to investigate the role of long-term HIV-1 viral protein exposure, the factor of biological sex, and their possible interaction, on synaptic dysfunction in MSNs of the NAc in the HIV-1 transgenic (Tg) rat. HIV-1 Tg rats, independent of biological sex, displayed profound alterations in synaptic connectivity, evidenced by a prominent shift in the distribution of dendritic spines. Female HIV-1 Tg rats, but not male HIV-1 Tg rats, exhibited alterations in dendritic branching and neuronal arbor complexity relative to control animals, supporting an alteration in glutamate neurotransmission. Morphologically, HIV-1 Tg male, but not female HIV-1 Tg rats, displayed a population shift towards decreased dendritic spine volume, suggesting decreased synaptic area, relative to control animals. Synaptic dysfunction accurately identified presence of the HIV-1 transgene, dependent upon biological sex, with at least 80% accuracy (i.e., Male: 80%; Female: 90%). Collectively, these results support a primary alteration in circuit connectivity, the mechanism of which is dependent upon biological sex. Understanding the effect of biological sex on the underlying neural mechanism for HIV-1 associated apathy is vital for the development of sex-based therapeutics and cure strategies.

What Is the Relationship between Dopamine and Effort?

The trade-off between reward and effort is at the heart of most behavioral theories, from ecology to economics. Compared to reward, however, effort remains poorly understood, both at the behavioral and neurophysiological levels. This is important because unwillingness to overcome effort to gain reward is a common feature of many neuropsychiatric and neurological disorders. A recent surge in interest in the neurobiological basis of effort has led to seemingly conflicting results regarding the role of dopamine. We argue here that, upon closer examination, there is actually striking consensus across studies: dopamine primarily codes for future reward but is less sensitive to anticipated effort cost. This strong association between dopamine and the incentive effects of rewards places dopamine in a key position to promote reward-directed action.

Computational modelling reveals distinct patterns of cognitive and physical motivation in elite athletes

Effort can be perceived both cognitively and physically, but the computational mechanisms underlying the motivation to invest effort in each domain remain unclear. In particular, it is unknown whether intensive physical training is associated with higher motivation specific to that domain, or whether it is accompanied by corresponding changes in cognitive motivation. Here, we tested a group of elite Oxford University rowers, and compared their behaviour to matched non-athletic controls. We trained participants on two tasks involving cognitive or physical effort. They then decided between a baseline low level of effort for low reward, versus higher levels of effort for higher rewards. Separate choices were made for the cognitive and physical tasks, which allowed us to computationally model motivation in each domain independently. As expected, athletes were willing to exert greater amounts of physical effort than non-athletes. Critically, however, the nature of cognitive effort-based decisions was different between groups, with a concave pattern of effort discounting for athletes but a convex pattern for non-athletes. These data suggest that the greater physical drive in athletes is accompanied by fundamentally different patterns of cognitive effort discounting, and suggests a complex relationship between motivation in the two domains.

The neuroanatomical and neurochemical basis of apathy and impulsivity in frontotemporal lobar degeneration

Apathy and impulsivity are common and often coexistent consequences of frontotemporal lobar degeneration (FTLD). They increase patient morbidity and carer distress, but remain under-estimated and poorly treated. Recent trans-diagnostic approaches that span the spectrum of clinical presentations of FTLD and parkinsonism, indicate that apathy and impulsivity can be fractionated into multiple neuroanatomical and pharmacological systems. These include ventral/dorsal fronto-striatal circuits for reward-sensitivity, response-inhibition, and decision-making; moderated by noradrenaline, dopamine, and serotonin. Improved assessment tools, formal models of cognition and behavior, combined with brain imaging and psycho-pharmacology, are creating new therapeutic targets and establishing principles for stratification in future clinical trials.

HIV-1 proteins dysregulate motivational processes and dopamine circuitry

Motivational alterations, such as apathy, in HIV-1+ individuals are associated with decreased performance on tasks involving frontal-subcortical circuitry. We used the HIV-1 transgenic (Tg) rat to assess effect of long-term HIV-1 protein exposure on motivated behavior using sucrose (1–30%, w/v) and cocaine (0.01–1.0 mg/kg/infusion) maintained responding with fixed-ratio (FR) and progressive-ratio (PR) schedules of reinforcement. For sucrose-reinforced responding, HIV-1 Tg rats displayed no change in EC₅₀ relative to controls, suggesting no change in sucrose reinforcement but had a downward shifted concentration-response curves, suggesting a decrease in response vigor. Cocaine-maintained responding was attenuated in HIV-1 Tg rats (FR1 0.33 mg/kg/infusion and PR 1.0 mg/kg/infusion). Dose-response tests (PR) revealed that HIV-1 Tg animals responded significantly less than F344 control rats and failed to earn significantly more infusions of cocaine as the unit dose increased. When choosing between cocaine and sucrose, control rats initially chose sucrose but with time shifted to a cocaine preference. In contrast, HIV-1 disrupted choice behaviors. DAT function was altered in the striatum of HIV-1 Tg rats; however, prior cocaine self-administration produced a unique effect on dopamine homeostasis in the HIV-1 Tg striatum. These findings of altered goal directed behaviors may determine neurobiological mechanisms of apathy in HIV-1+ patients.

18F-DOPA uptake parameters in glioma: effects of patients' characteristics and prior treatment history

OBJECTIVE

In amino acid positron emission tomography brain tumour imaging, tumour-to-background uptake parameters are often used for treatment monitoring. We studied the effects of patients' characteristics and anticancer treatments on ¹⁸F-fluoro-l-phenylalanine uptake of normal brain and tumour lesions, with particular emphasis on temozolomide (TMZ) chemotherapy.

METHODS

155 studies from 120 patients with glioma were analysed. Average uptake of normal background (standardized uptake value, SUVbckgr) and basal ganglia (SUVbg), as well as tumour-to-brain ratios (TBR) were compared between positron emission tomography/CT studies acquired before (Group A, n = 48), after (Group B, n = 50) or during (Group C, n = 57) TMZ treatment, using analysis of variance.

RESULTS

Overall, mean SUVbckgr and mean SUVbg were 1.06 ± 0.26 and 2.12 ± 0.47, respectively. Female had significantly higher SUVbckgr (p = 0.002) and SUVbg (p = 0.012) than male patients. Age showed a positive correlation with SUVbg (p = 0.001). In the overall cohort, there were significant effects of TMZ on SUVbckgr (p = 0.0237) and TBR (p = 0.0138). In particular, SUVbckgr was lower in Group C than in Group B (1.00 ± 0.25 vs 1.14 ± 0.31, p = 0.0173). Significant variations of SUVbckr could be observed in female only. TBR was significantly higher in Group C than in Group B (2.37 ± 0.54 vs 2.06 ± 0.38, p = 0.010). Variations of SUVbg between groups slightly missed significance (p = 0.0504).

CONCLUSION

Temozolomide chemotherapy and patients' characteristics, including gender and age, affect physiological [¹⁸F]-fluoro-l-phenylalanine uptake and, consequently, the calculation of TBRs. Advances in knowledge: For the first time, the effects of past or concurrent temozolomide chemotherapy on brain physiological amino acid uptake have been investigated. Such effects are relevant and should be taken into account when evaluating tumour-to-background ratios.