Amphetamine use disorder is associated with striatum hypoactivation during anticipation of loss and reward

BACKGROUND

Dysregulated ventral striatum function has been proposed as one important process occurring in individuals with substance use disorder. This study investigates the role of altered reward and loss anticipation, which is an important component of impaired decision-making, impulsivity, and vulnerability to relapse in individuals with amphetamine use disorder (AMP).

AIMS

To determine whether AMP is associated with blunted striatum, prefrontal cortex, and insula signals during win and loss anticipation.

METHODS

Participants with and without AMP (AMP+ n = 46, AMP- n = 90) from the Tulsa 1000 study completed a monetary incentive delay (MID) task during functional magnetic resonance imaging.

RESULTS

Group main effects indicated that: (1) AMP+ exhibited lower bilateral caudate/putamen and left nucleus accumbens signal than AMP- across anticipation of wins and losses; and (2) AMP+ showed slower reaction times than AMP- during loss anticipation. Group*condition interactions demonstrated that AMP+ exhibited greater right amygdala signal than AMP- while anticipating large wins, a pattern that reversed when anticipating small losses. Left caudate/putamen attenuations in AMP+ during small loss anticipation were also evident. Groups did not differ in prefrontal or insula signals.

CONCLUSIONS

AMP+ individuals have altered neural processing and response patterns during reward and loss anticipation, potentially reflecting impairments in dopamine function, which may influence their decision-making and reactions to different win/loss scenarios. These findings help to explain why AMP+ have difficulty with decision-making and exhibit a heightened focus on immediate rewards or punishments.

Neural Differences in Relation to Risk Preferences during Reward Processing: An Event-Related Potential Study

Inter-individual variability in risk preferences can be reflected in reward processing differences, making people risk-seekers or risk-averse. However, the neural correlates of reward processing in individuals with risk preferences remain unknown. Consequently, this event-related potential (ERP) study examined and compared electrophysiological correlates associated with different stages of reward processing in risk-seeking and risk-averse groups. Individuals scoring in the bottom and top 20% on the Balloon Analogue Risk Task (BART) were deemed risk-averse and risk-seeking, respectively. Participants engaged in a gambling task while their electroencephalogram (EEG) was recorded. Risk-seekers tended to choose high-risk options significantly more frequently than low-risk options, whereas risk-averse individuals chose low-risk options significantly more frequently than high-risk ones. All participants selected the low-risk alternative more slowly than the high-risk option. During the anticipation stage, the low-risk option elicited a relatively attenuated stimulus-preceding negativity (SPN) response from risk-seekers compared to risk-averse participants. During the outcome stage, feedback-related negativity (FRN) increased in risk-seekers responding to greater losses but not in risk-averse participants. These results indicate that ERP components can detect differences in reward processing during risky situations. In addition, these results suggest that motivation and cognitive control, along with their associated neural processes, may play a central role in differences in reward-based behavior between the two groups.

The effects of an 8-week mindful eating intervention on anticipatory reward responses in striatum and midbrain

Introduction

Accumulating evidence suggests that increased neural responses during the anticipation of high-calorie food play an important role in the tendency to overeat. A promising method for counteracting enhanced food anticipation in overeating might be mindfulness-based interventions (MBIs). However, the neural mechanisms by which MBIs can affect food reward anticipation are unclear. In this randomized, actively controlled study, the primary objective was to investigate the effect of an 8-week mindful eating intervention on reward anticipation. We hypothesized that mindful eating would decrease striatal reward anticipation responses. Additionally, responses in the midbrain-from which the reward pathways originate-were explored.

Methods

Using functional magnetic resonance imaging (fMRI), we tested 58 healthy participants with a wide body mass index range (BMI: 19-35 kg/m2), motivated to change their eating behavior. During scanning they performed an incentive delay task, measuring neural reward anticipation responses to caloric and monetary cues before and after 8 weeks of mindful eating or educational cooking (active control).

Results

Compared with the educational cooking intervention, mindful eating affected neural reward anticipation responses, with reduced caloric relative to monetary reward responses. This effect was, however, not seen in the striatum, but only in the midbrain. The secondary objective was to assess temporary and long-lasting (1 year follow-up) intervention effects on self-reported eating behavior and anthropometric measures [BMI, waist circumference, waist-to-hip-ratio (WHR)]. We did not observe effects of the mindful eating intervention on eating behavior. Instead, the control intervention showed temporary beneficial effects on BMI, waist circumference, and diet quality, but not on WHR or self-reported eating behavior, as well as long-lasting increases in knowledge about healthy eating.

Discussion

These results suggest that an 8-week mindful eating intervention may have decreased the relative salience of food cues by affecting midbrain but not striatal reward responses, without necessarily affecting regular eating behavior. However, these exploratory results should be verified in confirmatory research.The primary and secondary objectives of the study were registered in the Dutch Trial Register (NTR): NL4923 (NTR5025).

Maternal neglect alters reward-anticipatory behavior, social status stability, and reward circuit activation in adult male rats

Introduction

Adverse early life experiences affect neuronal growth and maturation of reward circuits that modify behavior under reward predicting conditions. Previous studies demonstrate that rats undergoing denial of expected reward in the form of maternal contact (DER-animal model of maternal neglect) during early post-natal life developed anhedonia, aggressive play-fight behaviors and aberrant prefrontal cortex structure and neurochemistry. Although many studies revealed social deficiency following early-life stress most reports focus on individual animal tasks. Thus, attention needs to be given on the social effects during group tasks in animals afflicted by early life adversity.

Methods

To investigate the potential impact of the DER experience on the manifestation of behavioral responses induced by natural rewards, we evaluated: 1) naïve adult male sexual preference and performance, and 2) anticipatory behavior during a group 2-phase food anticipation learning task composed of a context-dependent and a cue-dependent learning period.

Results

DER rats efficiently spent time in the vicinity of and initiated sexual intercourse with receptive females suggesting an intact sexual reward motivation and consummation. Interestingly, during the context-dependent phase of food anticipation training DER rats displayed a modified exploratory activity and lower overall reward-context association. Moreover, during the cue-dependent phase DER rats displayed a mild deficit in context-reward association while increased cue-dependent locomotion. Additionally, DER rats displayed unstable food access priority following food presentation. These abnormal behaviours were accompanied by overactivation of the ventral prefrontal cortex and nucleus accumbens, as assessed by pCREB levels.

Conclusions/discussion

Collectively, these data show that the neonatal DER experience resulted in adulthood in altered activation of the reward circuitry, interfered with the normal formation of context-reward associations, and disrupted normal reward access hierarchy formation. These findings provide additional evidence to the deleterious effects of early life adversity on reward system, social hierarchy formation, and brain function.

A Meta-Analysis of Neural Correlates of Reward Anticipation in Individuals at Clinical Risk for Schizophrenia

BACKGROUND

Aberrant striatal responses to reward anticipation have been observed in schizophrenia. However, it is unclear whether these dysfunctions predate the onset of psychosis, and whether reward anticipation is impaired in individuals at clinical high risk for schizophrenia (CHR).

METHODS

To examine the neural correlates of monetary anticipation in the prodromal phase of schizophrenia, we performed a whole-brain meta-analysis of thirteen functional neuroimaging studies that compared reward anticipation signals between CHR individuals and healthy controls (HC). Three databases (PubMed, Web of Science, and ScienceDirect) were systematically searched from 1 January 2000 to 1 May 2022.

RESULTS

Thirteen whole-brain functional magnetic resonance imaging (fMRI) studies including 318 CHR subjects and 426 HC were identified through comprehensive literature searches. Relative to HC, CHR subjects showed increased brain responses in the medial prefrontal cortex (mPFC) and anterior cingulate cortex (ACC), and decreased activation in the mesolimbic circuit, including the putamen, parahippocampal gyrus, insula, cerebellum, and supramarginal gyrus, during reward anticipation.

CONCLUSIONS

Our findings in the CHR group confirmed the existence of abnormal motivational-related activation during reward anticipation, thus demonstrating the pathophysiological characteristics of the risk populations. These results have the potential to lead to the early identification and more accurate prediction of subsequent psychosis, as well as a deeper understanding of the neurobiology of high-risk state of psychotic disorder.

Altered empathy correlates with reduced social and non-social reward anticipation in individuals with high social anhedonia

This study examined the correlations of affective and cognitive components of empathy with reward anticipation toward monetary and social incentives in individuals with social anhedonia (SocAnh). According to the scores on the Revised Social Anhedonia Scale, 109 participants were divided into high (n = 57) and low (n = 52) SocAnh groups. Empathy was assessed with the Questionnaire of Cognitive and Affective Empathy (QCAE) and the Interpersonal Reactivity Index (IRI) Scale. Social and non-social reward anticipations were assessed by the Social and Monetary Incentive Delay Tasks, respectively. We performed independent-sample t tests and repeated-measures ANOVAs to examine the group differences on empathy and reward anticipation. Correlation analyses between empathy and reward anticipation were conducted. Results showed that the high SocAnh group reported reduced scores on empathy and reward anticipation for monetary and social incentives compared to their low SocAnh counterparts. Correlation analysis further indicated that monetary reward anticipation correlated with cognitive empathy, while social reward anticipation correlated with affective empathy. Our findings suggested that participants with high SocAnh exhibited poorer empathy and reduced reward anticipation than those with low SocAnh level. More importantly, social and non-social reward anticipation may distinctly contribute to affective and cognitive components of empathy.

The Interplay between Reward-Relevant Life Events and Trait Reward Sensitivity in Neural Responses to Reward Cues

The reward hypersensitivity model posits that trait reward hypersensitivity should elicit hyper/hypo approach motivation following exposure to recent life events that activate (goal-striving and goal-attainment) or deactivate (goal-failure) the reward system, respectively. To test these hypotheses, eighty-seven young adults with high (HRew) versus moderate (MRew) trait reward sensitivity reported frequency of life events via the Life Event Interview. Brain activation was assessed during the fMRI Monetary Incentive Delay task. Greater exposure to goal-striving events was associated with higher nucleus accumbens (NAc) reward anticipation among HRew participants and lower orbitofrontal cortex (OFC) reward anticipation among MRew participants. Greater exposure to goal-failure events was associated with higher NAc and OFC reward anticipation only among HRew participants. This study demonstrated different neural reward anticipation (but not outcome) following reward-relevant events for HRew versus MRew individuals. Trait reward sensitivity and reward-relevant life events may jointly modulate reward-related brain function, with implications for understanding psychopathology.

Early life stress moderated the influence of reward anticipation on acute psychosocial stress responses

Recent studies suggest that reward anticipation decreases individuals' acute stress responses. However, individuals who have experienced early life stress (ELS) may have a blunted capacity for reward anticipation, which reduces its buffering effect on psychosocial stress responses. To investigate this phenomenon, 66 young adults completed the Trier Social Stress Test following a reward anticipation task, and their ELS levels were measured using the Childhood Trauma Questionnaire (CTQ). Meanwhile, the current study collected biological and psychological measures of stress by analysing cortisol levels, heart rates, heart rate variability (HRV) as well as subjective stress levels, in response to the Trier Social Stress test. Results showed that reward anticipation successfully decreased acute stress responses in general, and it also improved participants' HRV. However, this effect was more evident in individuals with low ELS than those with high ELS. These findings help us deepen understanding of the role of reward anticipation in fostering resilience under stress and the potentially important implications for individuals who have been exposed to ELS are also discussed.

Reward Processing and Circuit Dysregulation in Posttraumatic Stress Disorder

Past decades have witnessed substantial progress in understanding of neurobiological mechanisms that contribute to generation of various PTSD symptoms, including intrusive memories, physiological arousal and avoidance of trauma reminders. However, the neurobiology of anhedonia and emotional numbing in PTSD, that have been conceptualized as reward processing deficits - reward wanting (anticipation of reward) and reward liking (satisfaction with reward outcome), respectively, remains largely unexplored. Empirical evidence on reward processing in PTSD is rather limited, and no studies have examined association of reward processing abnormalities and neurocircuitry-based models of PTSD pathophysiology. The manuscript briefly summarizes "state of the science" of both human reward processing, and of PTSD implicated neurocircuitry, as well as empirical evidence of reward processing deficits in PTSD. We then summarize current gaps in the literature and outline key future directions, further illustrating it by the example of two alternative explanations of PTSD pathophysiology potentially affecting reward processing via different neurobiological pathways. Studying reward processing in PTSD will not only advance the understanding of their link, but also could enhance current treatment approaches by specifically targeting anhedonia and emotional symptoms in PTSD patients.

Neuronal representations of reward-predicting cues and outcome history with movement in the frontal cortex

Transformation of sensory inputs to goal-directed actions requires estimation of sensory-cue values based on outcome history. We conduct wide-field and two-photon calcium imaging of the mouse neocortex during classical conditioning with two cues with different water-reward probabilities. Although licking movement dominates the area-averaged activity over the whole dorsal neocortex, the dorsomedial frontal cortex (dmFrC) affects other dorsal frontal cortical activities, and its inhibition extinguishes differences in anticipatory licking between the cues. Many dorsal frontal and medial prefrontal cortical neurons are task related. Subsets of these neurons are more excited by the low-reward-predicting cue or unrewarded outcomes than by the high-reward-predicting cue or rewarded outcomes, respectively. Task-related activities of these neurons and the others are counterbalanced, so that population activity appears dominated by licking. The reward-predicting cue and outcome history are most strongly represented in dmFrC. Our results suggest that dmFrC is crucial for initiating cortical processes to select or inhibit action.

Influence of Reward Motivation on Directed Forgetting in Younger and Older Adults

An important feature of the memory system is the ability to forget, but aging is associated with declines in the ability to intentionally forget potentially due to declines in cognitive control. Despite cognitive deficits, older adults are sensitive to affective manipulations, such as reward motivation, and reward anticipation can improve older adults' memory performance. The goal of the current studies was to examine the effect of reward motivation on directed remembering and forgetting. Participants were healthy CloudResearch/Turk Prime workers aged 18-35 and 60-85. In Experiment 1, we conducted a typical item-method directed forgetting task using neutral words presented one at a time followed by a to-be-remembered (TBR) or to-be-forgotten (TBF) cue. A recognition memory test followed that included all words from the encoding task, as well as new words. We replicated prior findings of better memory for TBR compared to TBF items, but not typical age-related differences in recognition of TBF items. In Experiments 2-4, we repeated this paradigm except that in the second block of trials, each word was presented with a high ($0.75) or low ($0.01) reward cue indicating the value that could be earned if the item was successfully Remembered or Forgotten (depending on cue). During recognition, correct responses to target items (both TBR and TBF) resulted in the associated reward, but incorrect "old" responses resulted in a loss of $0.50. In three experiments, high rewards led to better memory for younger and older adults compared to low rewards, regardless of the directed cue to remember or forget the word. In Experiments 3 and 4, older adults showed typical deficits in directed forgetting, but this was across reward conditions. For older adults, there was no evidence that including reward motivation improved cognitive control abilities as high value reward anticipation did not improve directed forgetting. Instead, in line with hypotheses, high compared to low value reward anticipation leads to engagement of processes that result in better memory regardless of the TBR or TBF cue, and reward anticipation bolsters memory in a relatively automatic, rather than strategic, fashion that overrides one's ability to cognitively control encoding processes.

Cognitive control increases honesty in cheaters but cheating in those who are honest

Every day, we are faced with the conflict between the temptation to cheat for financial gains and maintaining a positive image of ourselves as being a "good person." While it has been proposed that cognitive control is needed to mediate this conflict between reward and our moral self-image, the exact role of cognitive control in (dis)honesty remains elusive. Here we identify this role, by investigating the neural mechanism underlying cheating. We developed a task which allows for inconspicuously measuring spontaneous cheating on a trial-by-trial basis in the MRI scanner. We found that activity in the nucleus accumbens promotes cheating, particularly for individuals who cheat a lot, while a network consisting of posterior cingulate cortex, temporoparietal junction, and medial prefrontal cortex promotes honesty, particularly in individuals who are generally honest. Finally, activity in areas associated with cognitive control (anterior cingulate cortex and inferior frontal gyrus) helped dishonest participants to be honest, whereas it enabled cheating for honest participants. Thus, our results suggest that cognitive control is not needed to be honest or dishonest per se but that it depends on an individual's moral default.

Regulatory Effects of Reward Anticipation and Target on Attention Processing of Emotional Stimulation

Studies suggest that reward and emotion are interdependent. However, there are discrepancies regarding the interaction between these variables. Some researchers speculate that the inconsistent findings may be due to different targets being used. Although reward and emotion both affect attention, it is not clear whether their impacts are independent. This study examined the impact of reward anticipation on emotion processing for different targets. A cue-target paradigm was used, and behavior and eye-tracking data were recorded in an emotion or sex recognition task under the conditions of reward and non-reward anticipation. The results showed that when the target was related to the emotional attribute of the stimulus, the reward promoted the processing target information, thereby generating reward-oriented attention. When the target was unrelated to the emotional attributes of the stimulus, the reward did not promote the processing target information, and at the same time, individuals had negative emotional biases toward the emotional faces. The results revealed that, in addition to affecting the attention to emotional faces independently, the target regulated the promotion of reward anticipation to emotional attention and attention bias toward negative stimuli.

Transdiagnostic Prediction of Affective, Cognitive, and Social Function Through Brain Reward Anticipation in Schizophrenia, Bipolar Disorder, Major Depression, and Autism Spectrum Diagnoses

The relationship between transdiagnostic, dimensional, and categorical approaches to psychiatric nosology is under intense debate. To inform this discussion, we studied neural systems linked to reward anticipation across a range of disorders and behavioral dimensions. We assessed brain responses to reward expectancy in a large sample of 221 participants, including patients with schizophrenia (SZ; n = 27), bipolar disorder (BP; n = 28), major depressive disorder (MD; n = 31), autism spectrum disorder (ASD; n = 25), and healthy controls (n = 110). We also characterized all subjects with an extensive test battery from which a cognitive, affective, and social functioning factor was constructed. These factors were subsequently related to functional responses in the ventral striatum (vST) and neural networks linked to it. We found that blunted vST responses were present in SZ, BP, and ASD but not in MD. Activation within the vST predicted individual differences in affective, cognitive, and social functioning across diagnostic boundaries. Network alterations extended beyond the reward network to include regions implicated in executive control. We further confirmed the robustness of our results in various control analyses. Our findings suggest that altered brain responses during reward anticipation show transdiagnostic alterations that can be mapped onto dimensional measures of functioning. They also highlight the role of executive control of reward and salience signaling in the disorders we study and show the power of systems-level neuroscience to account for clinically relevant behaviors.

Shared and dissociable features of apathy and reward system dysfunction in bipolar I disorder and schizophrenia

BACKGROUND

Bipolar disorder I (BD-I) is defined by episodes of mania, depression and euthymic states. These episodes are among other symptoms characterized by altered reward processing and negative symptoms (NS), in particular apathy. However, the neural correlates of these deficits are not well understood.

METHODS

We first assessed the severity of NS in 25 euthymic BD-I patients compared with 25 healthy controls (HC) and 27 patients with schizophrenia (SZ). Then, we investigated ventral (VS) and dorsal striatal (DS) activation during reward anticipation in a Monetary Incentive Delayed Task and its association with NS.

RESULTS

In BD-I patients NS were clearly present and the severity of apathy was comparable to SZ patients. Apathy scores in the BD-I group but not in the SZ group correlated with sub-syndromal depression scores. At the neural level, we found significant VS and DS activation in BD-I patients and no group differences with HC or SZ patients. In contrast to patients with SZ, apathy did not correlate with striatal activation during reward anticipation. Explorative whole-brain analyses revealed reduced extra-striatal activation in BD-I patients compared with HC and an association between reduced activation of the inferior frontal gyrus and apathy.

CONCLUSION

This study found that in BD-I patients apathy is present to an extent comparable to SZ, but is more strongly related to sub-syndromal depressive symptoms. The findings support the view of different pathophysiological mechanisms underlying apathy in the two disorders and suggest that extra-striatal dysfunction may contribute to impaired reward processing and apathy in BD-I.

An Adaptation of Pavlovian-to-Instrumental Transfer (PIT) Methodology to Examine the Energizing Effects of Reward-Predicting Cues on Behavior in Young Adults

There is growing recognition that much of human behavior is governed by the presence of classically conditioned cues. The Pavlovian-to-Instrumental Transfer (PIT) paradigm offers a way to measure the effects of classically conditioned stimuli on behavior. In the current study, a novel behavioral task, an adaptation of the PIT framework, was developed for use in conjunction with an fMRI classical conditioning task. Twenty-four healthy young adults completed (1) instrumental training, (2) Pavlovian conditioning, and (3) a Transfer test. During instrumental training, participants learned to apply force to a handgrip to win money from slot machines pictured on a computer screen. During Pavlovian conditioning, slot machines appeared with one of two abstract symbols (cues), one symbol was predictive of monetary reward. During the Transfer test, participants again applied force to a handgrip to win money. This time, the slot machines were presented with the Pavlovian cues, but with the outcomes hidden. The results indicated increased effort on the instrumental task, i.e. higher response frequency and greater force, in the presence of the reward-predicting cue. Our findings add to the growing number of studies demonstrating PIT effects in humans. This new paradigm is effective in measuring the effects of a conditioned stimulus on behavioral activation.

Emotional Contexts Modulate Anticipatory Late Positive Component and Reward Feedback Negativity in Adolescents With Major Depressive Disorder

BACKGROUND

Neuroimaging research has determined deficits in the dopaminergic circuit of major depressive disorder (MDD) during adolescence. This study investigated how emotional contexts modulate the temporal dynamics of reward anticipation and feedback in adolescents.

METHODS

EEG data from 35 MDD and 37 healthy adolescents were recorded when they conducted a gambling task after being presented with emotional pictures.

RESULTS

The results demonstrated that both MDD and healthy adolescents exhibited the largest late positive component (LPC) in positive contexts at the frontal sites and the largest LPC in negative contexts at the central sites; however, MDD adolescents exhibited anticipatory LPC hypoactivation than healthy adolescents. However, MDD adolescents exhibited smaller gain feedback negativity (FN) than healthy adolescents independent of emotional contexts, positively correlating with the trait anhedonia according to the consummatory aspect of the Temporal Experience of Pleasure Scale. In contrast, MDD adolescents exhibited greater FN loss in positive and neutral contexts than healthy adolescents while no difference in FN loss was found between the two groups in negative contexts. Moreover, the FN loss amplitudes negatively correlated with hedonic tone according to the Snaith-Hamilton Pleasure Scale over the past week.

CONCLUSIONS

These findings suggest that MDD adolescents exhibited dissociable deficits in reward anticipation and gain or loss feedback that are distinctly modulated by emotional contexts, and they deepen our understanding of the modulation of emotional contexts on the temporal dynamic reorganization of the reward circuit in MDD adolescents.

Neural Mechanisms Underlying Time Perception and Reward Anticipation

Findings suggest that the physiological mechanisms involved in the reward anticipation and time perception partially overlap. But the systematic investigation of a potential interaction between time and reward systems using neuroimaging is lacking. Eighteen healthy volunteers (all right-handed) participated in an event-related functional magnetic resonance imaging (fMRI) experiment that employs a visual paradigm that consists monetary reward to assess whether the functional neural representations of time perception and reward prospection are shared or distinct. Subjects performed a time perception task in which observers had to extrapolate the velocity of an occluded moving object in “reward” vs. “no-reward” sessions during fMRI scanning. There were also “control condition” trials in which participants judged about the color tone change of the stimuli. Time perception showed a fronto-parietal (more extensive in the right) cingulate and peristriate cortical as well as cerebellar activity. On the other hand, reward anticipation activated anterior insular cortex, nucleus accumbens, caudate nucleus, thalamus, cerebellum, postcentral gyrus, and peristriate cortex. Interaction between the time perception and the reward prospect showed dorsolateral, orbitofrontal, medial prefrontal and caudate nucleus activity. Our findings suggest that a prefrontal-striatal circuit might integrate reward and timing systems of the brain.

Reward anticipation revisited- evidence from an fMRI study in euthymic bipolar I patients and healthy first-degree relatives

BACKGROUND

Symptomatic phases in bipolar disorder (BD) are hypothesized to result from a hypersensitive behavioral activation system (BAS) being sensitive to potential rewards. However, studies on the neuronal underpinnings of reward anticipation in BD are scarce with contradictory findings and possibly confounded by effects of dopaminergic medication, necessitating further research on dysfunctional motivation in BD. Moreover, its role as vulnerability marker for BD is unclear.

METHODS

Functional imaging was conducted in 16 euthymic BD-I patients free from dopaminergic medication and 19 healthy first-degree relatives using a monetary incentive delay task and compared to parallelized control groups. Further, reward proneness, using the BIS/BAS questionnaire, and its relationship to neural reward anticipation was investigated.

RESULTS

BD-I patients displayed greater anterior cingulate cortex (ACC) activity during reward anticipation and higher BIS total scores compared to controls, with a positive relationship between the two measures. There were no neural or self-report group differences between relatives and controls.

LIMITATIONS

Due to the experimental design, the role of the ACC during receipt of reward remains unknown, sample sizes were rather small, and patients were not naïve to dopaminergic drugs, making an exclusion of medication effects on findings impossible.

CONCLUSIONS

Our findings give new insights on reward anticipation in BD. BD-I patients rated themselves as more risk avoidant and showed larger recruitment of the ACC rather than ventral striatum compared to controls during reward anticipation, possibly to down-regulate hyperactive limbic reward regions. This activation seems to be a consequence of rather than a vulnerability marker for the disorder.

Impact of a Common Genetic Variation Associated With Putamen Volume on Neural Mechanisms of Attention-Deficit/Hyperactivity Disorder

OBJECTIVE

In a recent genomewide association study of subcortical brain volumes, a common genetic variation at rs945270 was identified as having the strongest effect on putamen volume, a brain measurement linked to familial risk for attention-deficit/hyperactivity disorder (ADHD). To determine whether rs945270 might be a genetic determinant of ADHD, its effects on ADHD-related symptoms and neural mechanisms of ADHD, such as response inhibition and reward sensitivity, were explored.

METHOD

A large population sample of 1,834 14-year-old adolescents was used to test the effects of rs945270 on ADHD symptoms assessed through the Strengths and Difficulties Questionnaire and region-of-interest analyses of putamen activation by functional magnetic resonance imaging using the stop signal and monetary incentive delay tasks, assessing response inhibition and reward sensitivity, respectively.

RESULTS

There was a significant link between rs945270 and ADHD symptom scores, with the C allele associated with lower symptom scores, most notably hyperactivity. In addition, there were sex-specific effects of this variant on the brain. In boys, the C allele was associated with lower putamen activity during successful response inhibition, a brain response that was not associated with ADHD symptoms. In girls, putamen activation during reward anticipation increased with the number of C alleles, most significantly in the right putamen. Remarkably, right putamen activation during reward anticipation tended to negatively correlate with ADHD symptoms.

CONCLUSION

These results indicate that rs945270 might contribute to the genetic risk of ADHD partly through its effects on hyperactivity and reward processing in girls.

Trial-by-Trial Modulation of Associative Memory Formation by Reward Prediction Error and Reward Anticipation as Revealed by a Biologically Plausible Computational Model

Anticipation and delivery of rewards improves memory formation, but little effort has been made to disentangle their respective contributions to memory enhancement. Moreover, it has been suggested that the effects of reward on memory are mediated by dopaminergic influences on hippocampal plasticity. Yet, evidence linking memory improvements to actual reward computations reflected in the activity of the dopaminergic system, i.e., prediction errors and expected values, is scarce and inconclusive. For example, different previous studies reported that the magnitude of prediction errors during a reinforcement learning task was a positive, negative, or non-significant predictor of successfully encoding simultaneously presented images. Individual sensitivities to reward and punishment have been found to influence the activation of the dopaminergic reward system and could therefore help explain these seemingly discrepant results. Here, we used a novel associative memory task combined with computational modeling and showed independent effects of reward-delivery and reward-anticipation on memory. Strikingly, the computational approach revealed positive influences from both reward delivery, as mediated by prediction error magnitude, and reward anticipation, as mediated by magnitude of expected value, even in the absence of behavioral effects when analyzed using standard methods, i.e., by collapsing memory performance across trials within conditions. We additionally measured trait estimates of reward and punishment sensitivity and found that individuals with increased reward (vs. punishment) sensitivity had better memory for associations encoded during positive (vs. negative) prediction errors when tested after 20 min, but a negative trend when tested after 24 h. In conclusion, modeling trial-by-trial fluctuations in the magnitude of reward, as we did here for prediction errors and expected value computations, provides a comprehensive and biologically plausible description of the dynamic interplay between reward, dopamine, and associative memory formation. Our results also underline the importance of considering individual traits when assessing reward-related influences on memory.

Children with ADHD symptoms show decreased activity in ventral striatum during the anticipation of reward, irrespective of ADHD diagnosis

BACKGROUND

Changes in reward processing are thought to be involved in the etiology of attention-deficit/hyperactivity disorder (ADHD), as well as other developmental disorders. In addition, different forms of therapy for ADHD rely on reinforcement principles. As such, improved understanding of reward processing in ADHD could eventually lead to more effective treatment options. However, differences in reward processing may not be specific to ADHD, but may be a trans-diagnostic feature of disorders that involve ADHD-like symptoms.

METHODS

In this event-related fMRI study, we used a child-friendly version of the monetary incentive delay task to assess performance and brain activity during reward anticipation. Also, we collected questionnaire data to assess reward sensitivity in daily life. For final analyses, data were available for 27 typically developing children, 24 children with ADHD, and 25 children with an autism spectrum disorder (ASD) and ADHD symptoms.

RESULTS

We found decreased activity in ventral striatum during anticipation of reward in children with ADHD symptoms, both for children with ADHD as their primary diagnosis and in children with autism spectrum disorder and ADHD symptoms. We found that higher parent-rated sensitivity to reward was associated with greater anticipatory activity in ventral striatum for children with ADHD symptoms. In contrast, there was no relationship between the degree of ADHD symptoms and activity in ventral striatum.

CONCLUSIONS

We provide evidence of biological and behavioral differences in reward sensitivity in children with ADHD symptoms, regardless of their primary diagnosis. Ultimately, a dimensional brain-behavior model of reward sensitivity in children with symptoms of ADHD may be useful to refine treatment options dependent on reward processing.

Striatal dopamine, reward, and decision making in schizophrenia

Elevated striatal dopamine function is one of the best-established findings in schizophrenia. In this review, we discuss causes and consequences of this striata! dopamine alteration. We first summarize earlier findings regarding striatal reward processing and anticipation using functional neuroimaging. Secondly, we present a series of recent studies that are exemplary for a particular research approach: a combination of theory-driven reinforcement learning and decision-making tasks in combination with computational modeling and functional neuroimaging. We discuss why this approach represents a promising tool to understand underlying mechanisms of symptom dimensions by dissecting the contribution of multiple behavioral control systems working in parallel. We also discuss how it can advance our understanding of the neurobiological implementation of such functions. Thirdly, we review evidence regarding the topography of dopamine dysfunction within the striatum. Finally, we present conclusions and outline important aspects to be considered in future studies.

Chemogenetic inhibition of the medial prefrontal cortex reverses the effects of REM sleep loss on sucrose consumption

Rapid eye movement (REM) sleep loss is associated with increased consumption of weight-promoting foods. The prefrontal cortex (PFC) is thought to mediate reward anticipation. However, the precise role of the PFC in mediating reward responses to highly palatable foods (HPF) after REM sleep deprivation is unclear. We selectively reduced REM sleep in mice over a 25–48 hr period and chemogenetically inhibited the medial PFC (mPFC) by using an altered glutamate-gated and ivermectin-gated chloride channel that facilitated neuronal inhibition through hyperpolarizing infected neurons. HPF consumption was measured while the mPFC was inactivated and REM sleep loss was induced. We found that REM sleep loss increased HPF consumption compared to control animals. However, mPFC inactivation reversed the effect of REM sleep loss on sucrose consumption without affecting fat consumption. Our findings provide, for the first time, a causal link between REM sleep, mPFC function and HPF consumption.

DOI:http://dx.doi.org/10.7554/eLife.20269.001

Cue-Evoked Dopamine Release Rapidly Modulates D2 Neurons in the Nucleus Accumbens During Motivated Behavior

Dopaminergic neurons that project from the ventral tegmental area (VTA) to the nucleus accumbens (NAc) fire in response to unpredicted rewards or to cues that predict reward delivery. Although it is well established that reward-related events elicit dopamine release in the NAc, the role of rapid dopamine signaling in modulating NAc neurons that respond to these events remains unclear. Here, we examined dopamine's actions in the NAc in the rat brain during an intracranial self-stimulation task in which a cue predicted lever availability for electrical stimulation of the VTA. To distinguish actions of dopamine at select receptors on NAc neurons during the task, we used a multimodal sensor that probes three aspects of neuronal communication simultaneously: neurotransmitter release, cell firing, and identification of dopamine receptor type. Consistent with prior studies, we first show dopamine release events in the NAc both at cue presentation and after lever press (LP). Distinct populations of NAc neurons encode these behavioral events at these same locations selectively. Using our multimodal sensor, we found that dopamine-mediated responses after the cue involve exclusively a subset of D2-like receptors (D2Rs), whereas dopamine-mediated responses proximal to the LP are mediated by both D1-like receptors (D1R) and D2Rs. These results demonstrate for the first time that dopamine-mediated responses after cues that predict reward availability are specifically linked to its actions at a subset of neurons in the NAc containing D2Rs.

SIGNIFICANCE STATEMENT

Successful reward procurement typically involves the completion of a goal-directed behavior in response to appropriate environmental cues. Although numerous studies link the mesolimbic dopamine system with these processes, how dopamine's effects are mediated on the receptor level within a key neural substrate, the nucleus accumbens, remains elusive. Here, we used a unique multimodal sensor that reveals three aspects of neuronal interactions: neurotransmitter release, cell firing, and dopamine-receptor type. We identified a key role of D2-like receptor (D2R)-expressing neurons in response to a reward-predicting cue, whereas both the D2R and D1R types modulate responses of neurons proximal to the goal-directed action. This work provides novel insight into the unique role of D2R-mediated neuronal activity to reward-associated cues, a fundamental aspect of motivated behaviors.

Causal discovery in an adult ADHD data set suggests indirect link between DAT1 genetic variants and striatal brain activation during reward processing

Attention-deficit/hyperactivity disorder (ADHD) is a common and highly heritable disorder affecting both children and adults. One of the candidate genes for ADHD is DAT1, encoding the dopamine transporter. In an attempt to clarify its mode of action, we assessed brain activity during the reward anticipation phase of the Monetary Incentive Delay (MID) task in a functional MRI paradigm in 87 adult participants with ADHD and 77 controls (average age 36.5 years). The MID task activates the ventral striatum, where DAT1 is most highly expressed. A previous analysis based on standard statistical techniques did not show any significant dependencies between a variant in the DAT1 gene and brain activation [Hoogman et al. (2013); Neuropsychopharm 23:469-478]. Here, we used an alternative method for analyzing the data, that is, causal modeling. The Bayesian Constraint-based Causal Discovery (BCCD) algorithm [Claassen and Heskes (2012); Proceedings of the 28th Conference on Uncertainty in Artificial Intelligence] is able to find direct and indirect dependencies between variables, determines the strength of the dependencies, and provides a graphical visualization to interpret the results. Through BCCD one gets an opportunity to consider several variables together and to infer causal relations between them. Application of the BCCD algorithm confirmed that there is no evidence of a direct link between DAT1 genetic variability and brain activation, but suggested an indirect link mediated through inattention symptoms and diagnostic status of ADHD. Our finding of an indirect link of DAT1 with striatal activity during reward anticipation might explain existing discrepancies in the current literature. Further experiments should confirm this hypothesis. © 2015 Wiley Periodicals, Inc.

Influence of menarche on the relation between diurnal cortisol production and ventral striatum activity during reward anticipation

Adolescence is characterized by an increase in risk-taking and reward-seeking behaviors. In other populations, increased risk taking has been associated with tighter coupling between cortisol production and ventral striatum (VS) activation during reward anticipation; this relation has not yet been examined, however, as a function of adolescent development. This study examined the influence of pubertal development on the association between diurnal cortisol production and VS activity during reward anticipation. Pre- and post-menarcheal girls collected diurnal cortisol and completed an functional magnetic resonance imaging-based monetary incentive delay task, from which we extracted estimates of VS activity during the anticipation of reward, anticipation of loss and anticipation of non-incentive neutral trials. Post-menarcheal girls showed greater coupling between the cortisol awakening response and VS activation during anticipation of reward and loss than did their pre-menarcheal counterparts. Post-menarcheal girls did not differ from pre-menarcheal girls in their cortisol-VS coupling during anticipation of neutral trials, suggesting that puberty-related changes in cortisol-VS coupling are specific to affective stimuli. Interestingly, behavioral responses during the task indicate that post-menarcheal girls are faster to engage with affective stimuli than are pre-menarcheal girls. Thus, post-menarcheal girls exhibit neurobiological and behavioral patterns that have been associated with risk taking and that may underlie the dramatic increase in risk-taking behavior documented during adolescence.

Video game training and the reward system

Video games contain elaborate reinforcement and reward schedules that have the potential to maximize motivation. Neuroimaging studies suggest that video games might have an influence on the reward system. However, it is not clear whether reward-related properties represent a precondition, which biases an individual toward playing video games, or if these changes are the result of playing video games. Therefore, we conducted a longitudinal study to explore reward-related functional predictors in relation to video gaming experience as well as functional changes in the brain in response to video game training. Fifty healthy participants were randomly assigned to a video game training (TG) or control group (CG). Before and after training/control period, functional magnetic resonance imaging (fMRI) was conducted using a non-video game related reward task. At pretest, both groups showed strongest activation in ventral striatum (VS) during reward anticipation. At posttest, the TG showed very similar VS activity compared to pretest. In the CG, the VS activity was significantly attenuated. This longitudinal study revealed that video game training may preserve reward responsiveness in the VS in a retest situation over time. We suggest that video games are able to keep striatal responses to reward flexible, a mechanism which might be of critical value for applications such as therapeutic cognitive training.

Effect of brain structure and function on reward anticipation in children and adults with attention deficit hyperactivity disorder combined subtype

Attention deficit hyperactivity disorder (ADHD) is associated with decreased ventral-striatal responsiveness during reward anticipation. However, previous research mostly focused on adults with heterogeneous ADHD subtype and divers drug treatment status while studies in children with ADHD are sparse. Moreover, it remains unclear to what degree ADHD is characterized by a delay of normal brain structure or function maturation. We therefore attempt to determine whether results from structural and functional magnetic resonance imaging (fMRI) are associated with childhood and adult ADHD combined subtype (ADHD-CT). This study used fMRI to compare VS structure and function of 30 participants with ADHD-CT (16 adults, 14 children) and 30 controls (20 adults, 10 children), using a monetary incentive delay task. Joint analyses of structural and functional imaging data were conducted with Biological Parametric Mapping. Reward anticipation elicited decreased ventral-striatal responsiveness in adults but not in children with ADHD-CT. Children and adults with ADHD showed reduced ventral-striatal volume. Taking these gray matter differences into account, the results remained the same. These results suggest that decreased ventral-striatal responsiveness during reward anticipation is present in adults but not in children with ADHD-CT, irrespective of structural characteristics. The question arises whether ventral-striatal hypoactivity is an ADHD correlate that develops during the course of illness.

Differential patterns of nucleus accumbens activation during anticipation of monetary and social reward in young and older adults

Recent studies have reported inconsistent results regarding the loss of reward sensitivity in the aging brain. Although such an age effect might be due to a decline of physiological processes, it may also be a consequence of age-related changes in motivational preference for different rewards. Here, we examined whether the age effects on neural correlates of reward anticipation are modulated by the type of expected reward. Functional magnetic resonance images were acquired in 24 older (60-78 years) and 24 young participants (20-28 years) while they performed an incentive delay task offering monetary or social rewards. Anticipation of either reward type recruited brain structures associated with reward, including the nucleus accumbens (NAcc). Region of interest analysis revealed an interaction effect of reward type and age group in the right NAcc: enhanced activation to cues of social reward was detected in the older subsample while enhanced activation to cues of monetary reward was detected in the younger subsample. Our results suggest that neural sensitivity to reward-predicting cues does not generally decrease with age. Rather, neural responses in the NAcc appear to be modulated by the type of reward, presumably reflecting age-related changes in motivational value attributed to different types of reward.

Reward anticipation in the adolescent and aging brain

Processing of reward is the basis of adaptive behavior of the human being. Neural correlates of reward processing seem to be influenced by developmental changes from adolescence to late adulthood. The aim of this study is to uncover these neural correlates during a slot machine gambling task across the lifespan. Therefore, we used functional magnetic resonance imaging to investigate 102 volunteers in three different age groups: 34 adolescents, 34 younger adults, and 34 older adults. We focused on the core reward areas ventral striatum (VS) and ventromedial prefrontal cortex (VMPFC), the valence processing associated areas, anterior cingulate cortex (ACC) and insula, as well as information integration associated areas, dorsolateral prefrontal cortex (DLPFC), and inferior parietal lobule (IPL). Results showed that VS and VMPFC were characterized by a hyperactivation in adolescents compared with younger adults. Furthermore, the ACC and insula were characterized by a U-shape pattern (hypoactivation in younger adults compared with adolescents and older adults), whereas the DLPFC and IPL were characterized by a J-shaped form (hyperactivation in older adults compared with younger groups). Furthermore, a functional connectivity analysis revealed an elevated negative functional coupling between the inhibition-related area rIFG and VS in younger adults compared with adolescents. Results indicate that lifespan-related changes during reward anticipation are characterized by different trajectories in different reward network modules and support the hypothesis of an imbalance in maturation of striatal and prefrontal cortex in adolescents. Furthermore, these results suggest compensatory age-specific effects in fronto-parietal regions.

Touching moments: desire modulates the neural anticipation of active romantic caress

A romantic caress is a basic expression of affiliative behavior and a primary reinforcer. Given its inherent affective valence, its performance also would imply the prediction of reward values. For example, touching a person for whom one has strong passionate feelings likely is motivated by a strong desire for physical contact and associated with the anticipation of hedonic experiences. The present study aims at investigating how the anticipatory neural processes of active romantic caress are modulated by the intensity of the desire for affective contact as reflected by passionate feelings for the other. Functional magnetic resonance imaging scanning was performed in romantically involved partners using a paradigm that allowed to isolate the specific anticipatory representations of active romantic caress, compared with control caress, while testing for the relationship between neural activity and measures of feelings of passionate love for the other. The results demonstrated that right posterior insula activity in anticipation of romantic caress significantly co-varied with the intensity of desire for union with the other. This effect was independent of the sensory-affective properties of the performed touch, like its pleasantness. Furthermore, functional connectivity analysis showed that the same posterior insula cluster interacted with brain regions related to sensory-motor functions as well as to the processing and anticipation of reward. The findings provide insight on the neural substrate mediating between the desire for and the performance of romantic caress. In particular, we propose that anticipatory activity patterns in posterior insula may modulate subsequent sensory-affective processing of skin-to-skin contact.

The effects of monetary and social rewards on task performance in children and adolescents: liking is not enough

The current study compared the effects of reward anticipation on task performance in children and adolescents (8-16 years old) using monetary and various social rewards. Eighty-five typically developing children undertook the Monetary Incentive Delay (MID) task. Of these 44 also undertook the Social Incentive Delay (SID-basic) task where social reward was operationalized as a smiling face and spoken compliments. Forty-one children participated in the SID-plus where points were added to a pictogram with written compliments. In a preparatory validation study participants were asked howmuch they liked the SID-basic rewards.Results showed that there was an effect of reward size on accuracy and RT in both the MID task and SID-plus, but not SID-basic. Subjective value of the SID-basic rewards was rated higher with hypothesized increasing reward intensity. In conclusion, although the social rewards in SID-basic were liked by children andadolescents in the validation study, they had no effect on the behaviour. Only when points were added (SID-plus), anticipated social reward affected task performance. Thus our results highlight (i) the difference between likeability andreinforcing quality and (ii) the need for a quantifiable element to rewards for themto be reinforcing for children.

Remedial effects of motivational incentive on declining cognitive control in healthy aging and Parkinson's disease

The prospect of reward may provide a motivational incentive for optimizing goal-directed behavior. Animal work demonstrates that reward-processing networks and oculomotor-control networks in the brain are connected through the dorsal striatum, and that reward anticipation can improve oculomotor control via this nexus. Due perhaps to deterioration in dopaminergic striatal circuitry, goal-directed oculomotor control is subject to decline in healthy seniors, and even more in individuals with Parkinson's disease (PD). Here we examine whether healthy seniors and PD patients are able to utilize reward prospects to improve their impaired antisaccade performance. Results confirmed that oculomotor control declined in PD patients compared to healthy seniors, and in healthy seniors compared to young adults. However, the motivational incentive of reward expectation resulted in benefits in antisaccade performance in all groups alike. These findings speak against structural and non-modifiable decline in cognitive control functions, and emphasize the remedial potential of motivational incentive mechanisms in healthy as well as pathological aging.

The reward circuit: linking primate anatomy and human imaging

Although cells in many brain regions respond to reward, the cortical-basal ganglia circuit is at the heart of the reward system. The key structures in this network are the anterior cingulate cortex, the orbital prefrontal cortex, the ventral striatum, the ventral pallidum, and the midbrain dopamine neurons. In addition, other structures, including the dorsal prefrontal cortex, amygdala, hippocampus, thalamus, and lateral habenular nucleus, and specific brainstem structures such as the pedunculopontine nucleus, and the raphe nucleus, are key components in regulating the reward circuit. Connectivity between these areas forms a complex neural network that mediates different aspects of reward processing. Advances in neuroimaging techniques allow better spatial and temporal resolution. These studies now demonstrate that human functional and structural imaging results map increasingly close to primate anatomy.