DECISION UTILITY, THE BRAIN, AND PURSUIT OF HEDONIC GOALS

Neural correlates of choosing alcohol over a palatable food reward in humans

BACKGROUND

In a population of light and heavy, nontreatment seeking drinkers, we recently showed that choice for alcohol versus a concurrently available snack reward was sensitive to the relative cost of alcohol. Here, we examined the neural substrates of alcohol choice using functional magnetic resonance imaging (MRI) in a new sample of light and heavy drinkers.

METHODS

Participants were scanned during the Concurrent Alcohol Food Choice task, and collected points associated with the images of alcohol or snack rewards that they could redeem at the end of the experiment. As cost manipulation, point values were equal or varied so that they favored alcohol or the snack reward. Linear mixed-effects models were used for the analyses of behavioral and brain data.

RESULTS

In a replication of prior findings, alcohol choice was sensitive to the relative value of alcohol in both groups. Neural activations in, among others, orbitofrontal cortex and insula were associated to relative value during choice. In addition, we observed that choosing alcohol as opposed to snack engaged two separate sets of brain regions. We did not replicate our prior finding of increased choice preference for alcohol in heavy compared to light drinkers and found no between-group differences in brain activity.

CONCLUSIONS

Overall, we replicated intact sensitivity to relative costs of alcohol in heavy drinkers and found its associated brain activity regions involved in value and salience attribution. Alcohol choice engaged regions involved in value-based behavior while snack preference elicited activity in areas linked to externally oriented attention. The failure to replicate the between-group differences may be due to the artificial MRI environment or observed differences in personality traits.

Tuning the value of sweet food: Blocking sweet taste receptors increases the devaluation effect in a go/no-go task

Despite the apparent simplicity of the go/no-go (GNG) task, in which individuals selectively respond or withhold responses, there is strong evidence supporting its efficacy in terms of modulating food preferences. Herein, we manipulated sweet taste perception and investigated the no-go devaluation effect that is typically observed due to GNG training with respect to sweet and savory food items. Prior to engaging in a GNG task, one group of participants rinsed their mouths with a liquid solution containing gymnemic acid, thereby transiently and selectively inhibiting sweet taste perception, while another group used a placebo solution. The participants who rinsed their mouths with gymnemic acid exhibited a stronger overall decrease in food evaluations from pre to post training. Furthermore, a pronounced no-go devaluation effect was observed for sweet foods, irrespective of the rinsing solution. Overall, our results support the notion that training in the GNG task can induce changes in the valuation of food stimuli, particularly for sweet foods.

Choice of alcohol over a natural reward: an experimental study in light and heavy social drinkers

RATIONALE & OBJECTIVES

A core symptom of alcohol use disorder (AUD) is a progressively increased choice of alcohol over alternative rewards despite negative consequences. Here, we investigated choice between personalized alcohol vs. natural rewards in a laboratory setting, and compared this behavior between non-treatment-seeking heavy drinkers and light social drinkers.

METHODS

30 light social drinkers (15 men drinking < 15 drinks/week and 15 women drinking < 10 drinks/week) and 30 heavy, non-treatment-seeking drinkers (drinking more than these levels; 15 women). In the Concurrent Choice Alcohol Food (CCAF) task, participants chose between individually tailored images of alcohol and snack rewards and collected points towards the respective reward. To assess cost sensitivity, points associated to the images varied so that they favored alcohol or snack, or were equal, creating three relative point levels.

RESULTS

Choice preference for alcohol was strongly correlated with Alcohol Use Disorder Identification Test (AUDIT) scores, supporting the external validity of the choice procedure. Compared to light drinkers, heavy drinkers showed increased choice preference for alcohol, as indicated by a between-group difference in points of subjective equality, a metric that quantifies the relative point level at which alcohol and snacks were equally likely to be chosen. In both groups, choice preference strongly depended on the relative point level of alcohol compared to snacks, suggesting that responding for alcohol in heavy drinkers was sensitive to costs.

CONCLUSIONS

Our results replicate previous findings of a relationship between self-reported alcohol use and choice preference for alcohol. We also found that choice behavior was strongly dependent on relative cost of alcohol in both groups, although price sensitivity was lower in heavy compared to light drinkers. An increased choice preference for alcohol in heavy drinkers suggests that they attribute a higher relative reinforcing value to alcohol compared to natural rewards.

Stronger coupling of emotional instability with reward processing in borderline personality disorder is predicted by schema modes

BACKGROUND

Mood instability and risk-taking are hallmarks of borderline personality disorder (BPD). Schema modes are combinations of self-reflective evaluations, negative emotional states, and destructive coping strategies common in BPD. When activated, they can push patients with BPD into emotional turmoil and a dissociative state of mind. Our knowledge of the underlying neurocognitive mechanisms driving these changes is incomplete. We hypothesized that in patients with BPD, affective instability is more influenced by reward expectation, outcomes, and reward prediction errors (RPEs) during risky decision-making than in healthy controls. Additionally, we expected that these alterations would be related to schema modes.

METHODS

Thirty-two patients with BPD and thirty-one healthy controls were recruited. We used an established behavioral paradigm to measure mood fluctuations during risky decision-making. The impact of expectations and RPEs on momentary mood was quantified by a computational model, and its parameters were estimated with hierarchical Bayesian analysis. Model parameters were compared using High-Density Intervals.

RESULTS

We found that model parameters capturing the influence of RPE and Certain Rewards on mood were significantly higher in patients with BPD than in controls. These model parameters correlated significantly with schema modes, but not with depression severity.

CONCLUSIONS

BPD is coupled with altered associations between mood fluctuation and reward processing under uncertainty. Our findings seem to be BPD-specific, as they stand in contrast with the correlates of depressive symptoms. Future studies should establish the clinical utility of these alterations, such as predicting or assessing therapeutic response in BPD.

Dopamine-mediated striatal activity and function is enhanced in GlyRα2 knockout animals

The glycine receptor alpha 2 (GlyRα2) is a ligand-gated ion channel which upon activation induces a chloride conductance. Here, we investigated the role of GlyRα2 in dopamine-stimulated striatal cell activity and behavior. We show that depletion of GlyRα2 enhances dopamine-induced increases in the activity of putative dopamine D1 receptor-expressing striatal projection neurons, but does not alter midbrain dopamine neuron activity. We next show that the locomotor response to d-amphetamine is enhanced in GlyRα2 knockout animals, and that this increase correlates with c-fos expression in the dorsal striatum. 3-D modeling revealed an increase in the neuronal ensemble size in the striatum in response to D-amphetamine in GlyRα2 KO mice. Finally, we show enhanced appetitive conditioning in GlyRα2 KO animals that is likely due to increased motivation, but not changes in associative learning or hedonic response. Taken together, we show that GlyRα2 is an important regulator of dopamine-stimulated striatal activity and function.

Pain, from perception to action: A computational perspective

Pain is driven by sensation and emotion, and in turn, it motivates decisions and actions. To fully appreciate the multidimensional nature of pain, we formulate the study of pain within a closed-loop framework of sensory-motor prediction. In this closed-loop cycle, prediction plays an important role, as the interaction between prediction and actual sensory experience shapes pain perception and subsequently, action. In this Perspective, we describe the roles of two prominent computational theories-Bayesian inference and reinforcement learning-in modeling adaptive pain behaviors. We show that prediction serves as a common theme between these two theories, and that each of these theories can explain unique aspects of the pain perception-action cycle. We discuss how these computational theories and models can improve our mechanistic understandings of pain-centered processes such as anticipation, attention, placebo hypoalgesia, and pain chronification.

A meta-theoretical framework for organizing and integrating theory and research on motivation for health-related behavior

The concept of motivation is broad and multi-faceted. In health psychology, motivation has been conceptualized as cravings, urges, or desires for unhealthy behaviors, such as consumption of alcohol, cigarettes, or calorie-dense foods; or as behavioral intentions or proximal goals for healthy behaviors, such as smoking cessation, physical activity, or condom use. Because of the differences in terminology and associated theoretical underpinnings, it is difficult to characterize the state of the science or integrate research findings on motivation for health-related behavior. The present paper introduces a meta-theoretical Automatic-Reflective Motivation Framework (ARM-F) with the goals of organizing and integrating theory and research on motivation for health-related behaviors. At the first and broadest level, the ARM-F defines general motivation as a wanting or desire to do something. At the second level, it distinguishes between automatic and reflective motivation types, consistent with emerging perspectives in health psychology, historical and contemporary philosophical views on desire, and dual-processing perspectives in psychology. At the third level, the ARM-F preserves the nuanced terminologies and conceptualizations within the automatic (e.g., craving, urge, desire) and reflective (e.g., behavioral intention) motivation categories. The ARM-F has potential utility for organizing and integrating theory and research on motivation for health-related behavior, with implications for future research.

Alcohol solution strength preference predicts compulsive-like drinking behavior in rats

BACKGROUND

Understanding compulsive drinking behavior is key to improving outcomes in the treatment of addiction. In the present study, we investigated compulsive-like drinking in alcohol-addicted rats using the alcohol deprivation effect (ADE) model of relapse behavior, which involves repeated deprivation and reintroduction phases; the latter approximate relapse.

METHODS

High-resolution longitudinal drinking and locomotor data were measured while rats (n = 30) underwent a four-bottle (water, 5%, 10%, 20% alcohol v/v) free-choice ADE paradigm. Alcohol bottles were adulterated with the bitter compound quinine during a reintroduction phase to test for compulsive behavior. We characterized how drinking and locomotor behavior during ADE + quinine differed from a regular ADE and how, at the individual level, behavioral parameters extracted from the regular ADE related to compulsive-like drinking. Associations of drinking with locomotor activity were also examined.

RESULTS

In the ADE with quinine, we observed reduced consumption of alcohol and a shift to preference for stronger alcohol. Quinine acted by decreasing both the access size and frequency of drinking of 5% alcohol while increasing the frequency of consumption of 20% alcohol. Preference for higher alcohol concentrations prior to the quinine challenge was associated with greater compulsive-like drinking behavior; higher baseline consumption of 20% alcohol correlated with more drinking of quinine-adulterated solutions while high frequency and amount of 5% alcohol consumption at baseline were correlated with being more strongly affected by quinine. Associations between locomotor activity and drinking behavior were observed at the hourly level. These associations reflected changing preferences across experimental phases.

CONCLUSION

Drinking patterns, and specifically solution preference, may offer insights into the presentation of compulsive-like drinking. The findings provide a preclinical basis for observations from epidemiological studies that link higher risk and burden of alcohol-related disease to stronger alcohol concentrations and encourage further translational studies to better understand the underlying mechanisms.

Novelty detection in early olfactory processing of the honey bee, Apis mellifera

Animals are constantly bombarded with stimuli, which presents a fundamental problem of sorting among pervasive uninformative stimuli and novel, possibly meaningful stimuli. We evaluated novelty detection behaviorally in honey bees as they position their antennae differentially in an air stream carrying familiar or novel odors. We then characterized neuronal responses to familiar and novel odors in the first synaptic integration center in the brain-the antennal lobes. We found that the neurons that exhibited stronger initial responses to the odor that was to be familiarized are the same units that later distinguish familiar and novel odors, independently of chemical identities. These units, including both tentative projection neurons and local neurons, showed a decreased response to the familiar odor but an increased response to the novel odor. Our results suggest that the antennal lobe may represent familiarity or novelty to an odor stimulus in addition to its chemical identity code. Therefore, the mechanisms for novelty detection may be present in early sensory processing, either as a result of local synaptic interaction or via feedback from higher brain centers.

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.

Value, drug addiction and the brain

Over the years, various models have been proposed to explain the psychology and biology of drug addiction, built primarily around the habit and compulsion models. Recent research indicates drug addiction may be goal-directed, motivated by excessive valuation of drugs. Drug consumption may initially occur for the sake of pleasure but may transition to a means of escaping withdrawal, stress and negative emotions. In this hypothetical paper, we propose a value-based neurobiological model for drug addiction. We posit that during dependency, the value-based decision-making system in the brain is not inactive but has instead prioritized drugs as the reward of choice. In support of this model, we consider the role of valuation in choice, its influence on pleasure and punishment, and how valuation is contrasted in impulsive and compulsive behaviours. We then discuss the neurobiology of value, beginning with the dopaminergic system and its relationship with incentive salience before moving to brain-wide networks involved in valuation, control and prospection. These value-based neurobiological components are then integrated into the cycle of addiction as we consider the development of drug dependency from a valuation perspective. We conclude with a discussion of cognitive interventions utilizing value-based decision-making, highlighting not just advances in recalibrating the valuation system to focus on non-drug rewards, but also areas for improvement in refining this approach.

A Neural System that Represents the Association of Odors with Rewarded Outcomes and Promotes Behavioral Engagement

Odors are well known to elicit strong emotional and behavioral responses that become strengthened throughout learning, yet the specific cellular systems involved in odor learning and the direct influence of these on behavior are unclear. Here, we investigate the representation of odor-reward associations within two areas recipient of dense olfactory input, the posterior piriform cortex (pPCX) and the olfactory tubercle (OT), using electrophysiological recordings from mice engaged in reward-based learning. Neurons in both regions represent conditioned odors and do so with similar information content, yet the proportion of neurons recruited by conditioned rewarded odors and the magnitudes and durations of their responses are greater in the OT. Using fiber photometry, we find that OT D1-type dopamine-receptor-expressing neurons flexibly represent odors based on reward associations, and using optogenetics, we show that these neurons influence behavioral engagement. These findings contribute to a model whereby OT D1 neurons support odor-guided motivated behaviors.

Deep Brain Stimulation in the Nucleus Accumbens for Binge Eating Disorder: a Study in Rats

Binge eating disorder (BED), with its compulsive and addictive components, may often underlie weight regain after gastrointestinal bariatric surgeries. BED is therefore considered an exclusion criterion for these surgeries. Anecdotal reports suggest that deep brain stimulation (DBS) is an effective treatment for addictive disorders with, similar to BED, pathological changes in cerebral reward circuitry. We therefore assessed effect of DBS of the nucleus accumbens (NAC) in a rat model of BED. Twenty-one male obesity prone Wistar rats with DBS electrodes placed in NAC subregions were subjected to a binge eating protocol. Binge eating was significantly reduced with DBS during (NAC core) or before (NAC lateral shell) the binge. These outcomes provide a base to further explore the potential of DBS in the treatment of BED.

Why is active travel more satisfying than motorized travel? Evidence from Dublin

Some trips are better than others, and more and more studies find that active travel (walking and cycling) is more satisfying than motorized forms of travel (using the car or public transport). Why is this the case? Using data on travel satisfaction from 4134 commutes to a large University campus in Dublin, Ireland, this paper replicates the differences in travel satisfaction between active and motorized travel. We attribute these differences in large part to the duration of the trip. Subjective trip characteristics, such as safety and convenience, also play important roles. The trip duration explains rush-hour effects as well as why people starting from less affluent and more difficult-to-reach places are less satisfied with their trips. Longer-term policy options suggested by these results include infrastructure developments and spatial development strategies. A shorter-term initiative would be to delay university schedules in the morning to avoid low travel satisfaction during the slow rush-hour period and simultaneously ease pressure on the transport network at peak times.

Risk factors for heroin use following release from jail or prison in adults in a Central Appalachian state between 2012-2017

Background

Corrections-involved adults with a history of opioid use disorder are at elevated risk of opioid overdose following release from correctional settings. Increased opioid prescribing restrictions and monitoring during a time when heroin is becoming cheaper and ubiquitous means that adults who misused prescription opioids prior to incarceration may be reentering communities at greater risk for heroin exposure and use.

Objectives

Determine risk factors of post-release heroin use among a sample of adults who participated in corrections-based drug treatment in Kentucky released between 2012 and 2017.

Methods

Survey data obtained as part of an ongoing evaluation of corrections-based drug treatment were examined.

Results

The final sample (N = 1,563) was majority male (80.9%). Nearly 11.0% reported past-year heroin use following their release. Depressive symptoms, polydrug use, and urban proximity were more common among participants reporting post-release heroin use. Heroin use 30 days prior to incarceration was associated with a 432.1% increase in odds of heroin use subsequent to incarceration. Post-release suicidal ideation increased odds of heroin use by 154.2%, whereas reporting satisfaction from social interactions decreased odds of use by nearly 60%. Post-release use of cocaine and diverted buprenorphine were associated with increased likelihood of heroin use during this time period, increasing odds by 469.1% and 265.9%, respectively. Residing in Central Appalachia subsequent to incarceration was associated with decreased likelihood of use.

Conclusions

In this sample, post-release heroin use was associated with concerning features, such as polydrug use, lack of social satisfaction, and suicidal ideation. These features can serve as clear targets for clinical intervention.

Food Reward and Food Choice. An Inquiry Through The Liking and Wanting Model

What if consumers are getting obese because eating less calories is more difficult for persons that have a higher pleasure and desire towards food (Ikeda et al., 2005) and food companies do not help given only a two extreme option choice to satisfy their needs (i.e., low calories vs. high calories or healthy vs. unhealthy)? Reward systems are being described with a new conceptual approach where liking—the pleasure derived from eating a given food—and wanting—motivational value, desire, or craving—can be seen as the significant forces guiding eating behavior. Our work shows that pleasure (liking), desire (wanting), and the interaction between them influence and are good predictors of food choice and food intake. Reward responses to food are closely linked to food choice, inducing to caloric overconsumption. Based on the responses given to a self-administered questionnaire measuring liking and wanting attitudes, we found three different segments named ‘Reward lovers,’ ‘Half epicurious,’ and ‘Non indulgents’. Their behavior when choosing food is quite different. Results show differential effects on caloric consumption depending on segments. The introduction of more food choices that try to balance their content is a win-win strategy for consumers, companies, and society.

Task-Demand-Dependent Neural Representation of Odor Information in the Olfactory Bulb and Posterior Piriform Cortex

In awake rodents, the neural representation of olfactory information in the olfactory bulb is largely dependent on brain state and behavioral context. Learning-modified neural plasticity has been observed in mitral/tufted cells, the main output neurons of the olfactory bulb. Here, we propose that the odor information encoded by mitral/tufted cell responses in awake mice is highly dependent on the behavioral task demands. We used fiber photometry to record calcium signals from the mitral/tufted cell population in awake, head-fixed male mice under different task demands. We found that the mitral/tufted cell population showed similar responses to two distinct odors when the odors were presented in the context of a go/go task, in which the mice received a water reward regardless of the identity of the odor presented. However, when the same odors were presented in a go/no-go task, in which one odor was rewarded and the other was not, then the mitral cell population responded very differently to the two odors, characterized by a robust reduction in the response to the nonrewarded odor. Thus, the representation of odors in the mitral/tufted cell population depends on whether the task requires discrimination of the odors. Strikingly, downstream of the olfactory bulb, pyramidal neurons in the posterior piriform cortex also displayed a task-demand-dependent neural representation of odors, but the anterior piriform cortex did not, indicating that these two important higher olfactory centers use different strategies for neural representation.SIGNIFICANCE STATEMENT The most important task of the olfactory system is to generate a precise representation of odor information under different brain states. Whether the representation of odors by neurons in olfactory centers such as the olfactory bulb and the piriform cortex depends on task demands remains elusive. We find that odor representation in the mitral/tufted cells of the olfactory bulb depends on whether the task requires odor discrimination. A similar neural representation is found in the posterior piriform cortex but not the anterior piriform cortex, indicating that these higher olfactory centers use different representational strategies. The task-demand-dependent representational strategy is likely important for facilitating information processing in higher brain centers responsible for decision making and encoding of salience.

Drinking Levels and Profiles of Alcohol Addicted Rats Predict Response to Nalmefene

Background: Pharmacotherapeutic options supporting the treatment of alcohol dependence are recommended and available but underutilized, partly due to questions about efficacy. Nalmefene, a μ-opioid receptor antagonist and partial kappa receptor agonist, is recommended for reduction of alcohol consumption, but evidence about its effectiveness has been equivocal; identifying factors which predict response will help optimize treatment.

Methods: The alcohol deprivation effect paradigm is a tightly controlled procedure comprising repeated deprivation and reintroduction phases, leading to increased preference for alcohol; reintroduction approximates relapse. Using a digital drinkometer system measuring high-resolution drinking behavior, we examined the effects of nalmefene on relapse drinking behavior in alcohol addicted rats. We also tested whether drinking behavior in the relapse phase prior to nalmefene administration predicted treatment response. We further examined whether longitudinal drinking behavior and locomotor activity predicted treatment response.

Results: Our results showed that nalmefene (0.3 mg/kg) reduced relapse-like consumption significantly (∼20%) compared to vehicle on the first 2 days of alcohol reintroduction. Examining the first 6 h of a preceded treatment-free relapse episode revealed drinking patterns clustering the rats into responders (reduction of >40%, n = 17) and non-responders (reduction of <40%, n = 7) to subsequent nalmefene treatment. During the first 6 h of the preceding relapse phase, responders consumed more alcohol than non-responders; the amount of alcohol consumed during each drinking approach was larger but frequency of drinking did not differ. Longitudinal drinking behavior and locomotor activity did not significantly predict response.

Conclusion: Our results suggest that nalmefene reduces alcohol intake during a relapse-like situation but effectiveness can differ greatly at the individual level. However, who responds may be informed by examining drinking profiles and rats that show high drinking levels prior to treatment are more likely to respond to nalmefene.

Selective Attention Controls Olfactory Decisions and the Neural Encoding of Odors

Critical animal behaviors, especially among rodents, are guided by odors in remarkably well-coordinated manners, yet many extramodal sensory cues compete for cognitive resources in these ecological contexts. That rodents can engage in such odor-guided behaviors suggests that they can selectively attend to odors. Indeed, higher-order cognitive processes-such as learning, memory, decision making, and action selection-rely on the proper filtering of sensory cues based on their relative salience. We developed a behavioral paradigm to reveal that rats are capable of selectively attending to odors in the presence of competing extramodal stimuli. We found that this selective attention facilitates accurate odor-guided decisions, which become further strengthened with experience. Further, we uncovered that selective attention to odors adaptively sharpens their representation among neurons in the olfactory tubercle, an olfactory cortex region of the ventral striatum that is considered integral for evaluating sensory information in the context of motivated behaviors. Odor-directed selective attention exerts influences during moments of heightened odor anticipation and enhances odorant representation by increasing stimulus contrast in a signal-to-noise-type coding scheme. Together, these results reveal that rats engage selective attention to optimize olfactory outcomes. Further, our finding of attention-dependent coding in the olfactory tubercle challenges the notion that a thalamic relay is integral for the attentional control of sensory coding.

Biological markers for anxiety disorders, OCD and PTSD: A consensus statement. Part II: Neurochemistry, neurophysiology and neurocognition

OBJECTIVE

Biomarkers are defined as anatomical, biochemical or physiological traits that are specific to certain disorders or syndromes. The objective of this paper is to summarise the current knowledge of biomarkers for anxiety disorders, obsessive-compulsive disorder (OCD) and posttraumatic stress disorder (PTSD).

METHODS

Findings in biomarker research were reviewed by a task force of international experts in the field, consisting of members of the World Federation of Societies for Biological Psychiatry Task Force on Biological Markers and of the European College of Neuropsychopharmacology Anxiety Disorders Research Network.

RESULTS

The present article (Part II) summarises findings on potential biomarkers in neurochemistry (neurotransmitters such as serotonin, norepinephrine, dopamine or GABA, neuropeptides such as cholecystokinin, neurokinins, atrial natriuretic peptide, or oxytocin, the HPA axis, neurotrophic factors such as NGF and BDNF, immunology and CO2 hypersensitivity), neurophysiology (EEG, heart rate variability) and neurocognition. The accompanying paper (Part I) focuses on neuroimaging and genetics.

CONCLUSIONS

Although at present, none of the putative biomarkers is sufficient and specific as a diagnostic tool, an abundance of high quality research has accumulated that should improve our understanding of the neurobiological causes of anxiety disorders, OCD and PTSD.

Altered subjective reward valuation among drug-deprived heavy marijuana users: Aversion to uncertainty

Marijuana is the most commonly used illicit drug in the United States and its use is rising. Nonetheless, scientific efforts to clarify the risk for addiction and other harm associated with marijuana use have been lacking. Maladaptive decision-making is a cardinal feature of addiction that is likely to emerge in heavy users. In particular, distorted subjective reward valuation related to homeostatic or allostatic processes has been implicated for many drugs of abuse. Selective changes in responses to uncertainty have been observed in response to intoxication and deprivation from various drugs of abuse. To assess for these potential neuroadaptive changes in reward valuation associated with marijuana deprivation, we examined the subjective value of uncertain and certain rewards among deprived and nondeprived heavy marijuana users in a behavioral economics decision-making task. Deprived users displayed reduced valuation of uncertain rewards, particularly when these rewards were more objectively valuable. This uncertainty aversion increased with increasing quantity of marijuana use. These results suggest comparable decision-making vulnerability from marijuana use as other drugs of abuse, and highlights targets for intervention.

Possible role of a dysregulation of the endogenous opioid system in antisocial personality disorder

Around half the inmates in prison institutions have antisocial personality disorder (ASPD). A recent theory has proposed that a dysfunction of the endogenous opioid system (EOS) underlies the neurobiology of borderline personality disorder (BPD). In the present theoretical paper, based on a comprehensive database and hand search of the relevant literature, this hypothesis is extended to ASPD, which may be the predominant expression of EOS dysfunction in men, while the same pathology underlies BPD in women. According to evidence from human and animal studies, the problematic behaviours of persons with antisocial, callous, or psychopathic traits may be seen as desperate, unconscious attempts to stimulate their deficient EOS, which plays a key role in brain reward circuits. If the needs of this system are not being met, the affected persons experience dysphoric mood, discomfort, or irritability, and strive to increase binding of endogenous opioids to receptors by using the rewarding effects of aggression by exertion of physical or manipulative power on others, by abusing alcohol or substances that have the reward system as target, by creating an "endorphin rush" by self-harm, by increasing the frequency of their sexual contacts, or by impulsive actions and sensation seeking. Symptoms associated with ASPD can be treated with opioid antagonists like naltrexone, naloxone, or nalmefene.

Implicit measures of "wanting" and "liking" in humans

Incentive Sensitization Theory (IST; e.g., Robinson and Berridge, 1993. Brain Res. Rev., 18, 291; Robinson and Berridge, 2003 Trends Neurosci., 26, 507) suggests that a common dopamine system that deals with incentive salience attribution is affected by different types of drugs. Repeated drug use will sensitize this neural system, which means that drugs increasingly trigger the experience of incentive salience or "wanting". Importantly, Robinson and Berridge stress that there is a dissociation between drug "wanting" (the unconscious attribution of incentive salience) and drug "liking" (the unconscious hedonic experience when one consumes drugs). Whereas the former plays an essential role in the development and maintenance of drug addiction, the latter does not. Although this model was based mainly on research with non-human animals, more recently the dissociation between "wanting" and "liking" has been examined in humans as well. A widely used and promising means of studying these processes are behavioral implicit measures such as the Implicit Association Test (IAT), the Approach-Avoidance Task (AAT), different types of Stimulus-Response Compatibility (SRC) tasks, and Affective Simon Tasks (AST). IST makes the clear prediction that (1) there should be a positive correlation between indices of "wanting" (e.g., drug consumption) and implicit "wanting" scores. Similarly, there should be a positive correlation between indices of "liking" (e.g., various expressions of subjective pleasure) and implicit "liking" scores; (2) there should be higher "wanting" scores in substance abusers or frequent substance users compared to non-users or infrequent users, and there should be no differences in "liking" between these groups (or even less "liking" in frequent substance users); (3) manipulations of "wanting" should affect implicit "wanting" scores whereas manipulations of "liking" should affect implicit "liking" scores. However, studies that tested these hypotheses did not produce equivocal results. To shed light on these discrepancies, we first discuss the different definitions of "wanting" and "liking" and the different tests that have been used to assess these processes. Then, we discuss whether it is reasonable to assume that these tests are valid measures of "wanting" and "liking" and we review correlational, quasi-experimental, and experimental studies that inform us about this issue. Finally, we discuss the future potential of implicit measures in research on IST and make several recommendations to improve both theory and methodology.

Received Wisdom Regarding the Roles of Craving and Dopamine in Addiction: A Response to Lewis's Critique of Addiction: A Disorder of Choice

Lewis's review of my book (2011, this issue) repeats widely shared understandings of the nature of addiction and the role that dopamine plays in the persistence of self-destructive drug use. These accounts depict addiction as a chronic relapsing disease and claim that drug-induced changes in dopamine function explain the transition from drug experimentation to compulsive drug use. In my book, I test the idea that addiction is a chronic, persistent state. Lewis fails to mention the results of the various tests, although they provide a handy test for his account of addiction and are surprising in light of the common verbal formula "addiction is a chronic, relapsing disease." Consequently, I review a few of the key findings in this response. Lewis faults me for not giving enough attention to dopamine. In my book, I conclude that there is more to the biology of addiction than dopamine, and in this response, I describe research that tests the idea that drug-induced increases in dopamine markedly reduce an individual's capacity to choose nondrug reinforcers. In one experiment, rats readily gave up cocaine for saccharin, even when they had been consuming massive amounts of the drug for weeks. Put more generally, well-established research results call for a revision of currently accepted understandings of addiction and the role that dopamine plays in drug use.

The olfactory tubercle encodes odor valence in behaving mice

Sensory information acquires meaning to adaptively guide behaviors. Despite odors mediating a number of vital behaviors, the components of the olfactory system responsible for assigning meaning to odors remain unclear. The olfactory tubercle (OT), a ventral striatum structure that receives monosynaptic input from the olfactory bulb, is uniquely positioned to transform odor information into behaviorally relevant neural codes. No information is available, however, on the coding of odors among OT neurons in behaving animals. In recordings from mice engaged in an odor discrimination task, we report that the firing rate of OT neurons robustly and flexibly encodes the valence of conditioned odors over identity, with rewarded odors evoking greater firing rates. This coding of rewarded odors occurs before behavioral decisions and represents subsequent behavioral responses. We predict that the OT is an essential region whereby odor valence is encoded in the mammalian brain to guide goal-directed behaviors.

Cognitive manifestations of drinking-smoking associations: preliminary findings with a cross-primed Stroop task

BACKGROUND

Despite tremendous growth in research examining the role of cognitive bias in addictive behaviors, scant consideration has been paid to the close association between smoking and drinking behavior. This study sought to determine whether an association between smoking and drinking could be observed at an implicit level using a novel cognitive bias task, as well as characterize the relationship between performance on this task and clinically relevant variables (i.e., heaviness of use/dependence).

METHODS

Individuals (N=51) with a range of smoking and drinking patterns completed a modified Stroop task in which participants identified the color of drinking, smoking and neutral words that were each preceded by drinking, smoking or neutral picture primes. Participants also provided information regarding the heaviness of their smoking and drinking behavior and completed self-report measures of alcohol and nicotine dependence.

RESULTS

Response times to smoking and drinking words were significantly slowed following the presentation of either smoking or drinking picture primes. This effect did not differ across subgroups. However, the strength of the coupling between smoking and drinking prime effects was greater among heavier drinkers, who also exhibited a concordant looser coupling of the effects of smoking and drinking primes on smoking words.

CONCLUSIONS

Associations between smoking and drinking can be observed at an implicit level and may be strongest for heavier drinkers.

Neurobiological underpinnings of reward anticipation and outcome evaluation in gambling disorder

Gambling disorder is characterized by persistent and recurrent maladaptive gambling behavior, which leads to clinically significant impairment or distress. The disorder is associated with dysfunctions in the dopamine system. The dopamine system codes reward anticipation and outcome evaluation. Reward anticipation refers to dopaminergic activation prior to reward, while outcome evaluation refers to dopaminergic activation after reward. This article reviews evidence of dopaminergic dysfunctions in reward anticipation and outcome evaluation in gambling disorder from two vantage points: a model of reward prediction and reward prediction error by Wolfram Schultz et al. and a model of “wanting” and “liking” by Terry E. Robinson and Kent C. Berridge. Both models offer important insights on the study of dopaminergic dysfunctions in addiction, and implications for the study of dopaminergic dysfunctions in gambling disorder are suggested.

Short-term quetiapine treatment alters the use of reinforcement signals during risky decision-making and promotes the choice of negative expected values in healthy adult males

Effective decision-making can involve using environmental signals about the possible good and bad outcomes, and their probabilities, to select optimal actions. Problematic decision-making in psychiatric disorders, and particularly bipolar illness, may result from disrupted use of these reinforcement cues, leading to actions that reflect or precipitate pathological changes in mood. Previous experiments indicate that the processing of reinforcement cues while selecting between risky actions can be influenced by dopamine and serotonin activity. Quetiapine is an atypical antipsychotic agent with a complex pharmacology, including antagonist actions at 5-HT2A and, to a lesser extent, D2 receptors. Here, we investigated the effects of (short-term) treatment with quetiapine on the risky decision-making of healthy human adults. Twenty participants received 150 mg of quetiapine XL for 7 d, whereas 20 age- and IQ-matched participants received a placebo. On the eighth day, all participants completed a risky decision-making task that involved making a series of choices between two simultaneously presented gambles that differed in the magnitudes of their possible gains and losses, and the probabilities with which these outcomes were delivered. Quetiapine treatment was associated with a marked tendency to choose options with negative expected values compared with placebo treatment in male but not female participants. Our results demonstrate that antagonism of serotonin and dopamine receptor activity can alter the way individuals use information about gains and losses when selecting between risky actions, possibly reflecting gender-specific differences in risk attitudes. These effects may be beneficial by correcting decision-making biases that feature in mood disorders.

Neuroscientific model of motivational process

Considering the neuroscientific findings on reward, learning, value, decision-making, and cognitive control, motivation can be parsed into three sub processes, a process of generating motivation, a process of maintaining motivation, and a process of regulating motivation. I propose a tentative neuroscientific model of motivational processes which consists of three distinct but continuous sub processes, namely reward-driven approach, value-based decision-making, and goal-directed control. Reward-driven approach is the process in which motivation is generated by reward anticipation and selective approach behaviors toward reward. This process recruits the ventral striatum (reward area) in which basic stimulus-action association is formed, and is classified as an automatic motivation to which relatively less attention is assigned. By contrast, value-based decision-making is the process of evaluating various outcomes of actions, learning through positive prediction error, and calculating the value continuously. The striatum and the orbitofrontal cortex (valuation area) play crucial roles in sustaining motivation. Lastly, the goal-directed control is the process of regulating motivation through cognitive control to achieve goals. This consciously controlled motivation is associated with higher-level cognitive functions such as planning, retaining the goal, monitoring the performance, and regulating action. The anterior cingulate cortex (attention area) and the dorsolateral prefrontal cortex (cognitive control area) are the main neural circuits related to regulation of motivation. These three sub processes interact with each other by sending reward prediction error signals through dopaminergic pathway from the striatum and to the prefrontal cortex. The neuroscientific model of motivational process suggests several educational implications with regard to the generation, maintenance, and regulation of motivation to learn in the learning environment.

From prediction error to incentive salience: mesolimbic computation of reward motivation

Reward contains separable psychological components of learning, incentive motivation and pleasure. Most computational models have focused only on the learning component of reward, but the motivational component is equally important in reward circuitry, and even more directly controls behavior. Modeling the motivational component requires recognition of additional control factors besides learning. Here I discuss how mesocorticolimbic mechanisms generate the motivation component of incentive salience. Incentive salience takes Pavlovian learning and memory as one input and as an equally important input takes neurobiological state factors (e.g. drug states, appetite states, satiety states) that can vary independently of learning. Neurobiological state changes can produce unlearned fluctuations or even reversals in the ability of a previously learned reward cue to trigger motivation. Such fluctuations in cue-triggered motivation can dramatically depart from all previously learned values about the associated reward outcome. Thus, one consequence of the difference between incentive salience and learning can be to decouple cue-triggered motivation of the moment from previously learned values of how good the associated reward has been in the past. Another consequence can be to produce irrationally strong motivation urges that are not justified by any memories of previous reward values (and without distorting associative predictions of future reward value). Such irrationally strong motivation may be especially problematic in addiction. To understand these phenomena, future models of mesocorticolimbic reward function should address the neurobiological state factors that participate to control generation of incentive salience.

Neuropsychological Functions of μ- and δ-Opioid Systems

Brain opioid innervation is involved in many pathophysiological processes related to drug addiction. The main idea of the present review is that μ-/δ-opioid innervation is an intrinsic component of the motor/approach behavior network, which is activated synergetically with dopaminergic mesocorticolimbic network. Contribution of opioid innervation to the motor/approach behavior processing includes generation of positive emotions and inhibition of pain and stress reactions in order that the individual would be able to reach the vital goal. We cite the neuroanatomical data which showed that motor subcortical nuclei contain the most abundant opioid innervation and its activation is an obligatory component of positive emotions. In the majority of life situations, motor/approach behavior network concomitantly activates pain/stress control opioid network. Intensive cognitive activity induces activation of opioid innervation as well, and both enhancing and impairing effects of opioid agonists on cognitive functioning were demonstrated. Overall, the functioning of endogenous opioid networks may be summarized as following: NO physical/cognitive activity = NO positive emotions plus NO pain/stress control. We suppose that contemporary findings concerning neuropsychological functions of endogenous opioid system explain many controversial issues in neuropsychiatric conditions predisposing to drug addiction and neurological mechanisms of opioid addiction.

Contributions of Philip Teitelbaum to affective neuroscience

As part of a festschrift issue for Philip Teitelbaum, I offer here the thesis that Teitelbaum deserves to be viewed as an important forefather to the contemporary field of affective neuroscience (which studies motivation, emotion and affect in the brain). Teitelbaum's groundbreaking analyses of motivation deficits induced by lateral hypothalamic damage, of roles of food palatability in revealing residual function, and of recovery of 'lost' functions helped shape modern understanding of how motivation circuits operate within the brain. His redefinition of the minimum requirement for identifying motivation raised the conceptual bar for thinking about the topic among behavioral neuroscientists. His meticulous analyses of patterned stages induced by brain manipulations, life development and clinical disorders added new dimensions to our appreciation of how brain systems work. His steadfast highlighting of integrative functions and behavioral complexity helped provide a healthy functionalist counterbalance to reductionist trends in science of the late 20th century. In short, Philip Teitelbaum can be seen to have made remarkable contributions to several domains of psychology and neuroscience, including affective neuroscience.

Worry as a Predictor of Nutrition Behaviors

Worry has been shown to predict a variety of health behaviors, such as cancer screening, yet there are few studies linking worry and nutrition. This study used nationally representative data from National Cancer Institute’s Food Attitudes and Behavior Survey ( n = 3,397) to examine the association between health-related worry and a variety of nutrition behaviors. Greater worry was associated with higher fruit and vegetable consumption ( B = 0.19, p < .01), but also more meals eaten when watching television ( B = 0.34, p < .01) and fewer with family ( B = −0.13, p = .02). Importantly, and counterintuitively, greater worry appeared to reverse the conventional relationship between self-efficacy and dietary restriction; those who were self-efficacious and worried were less likely to restrict unhealthy foods. Similarly, worry attenuated the relationship between perceived benefits and special effort to buy produce. A complex relationship between worry and nutrition emerged, with potentially important clinical implications.

Led into temptation? Rewarding brand logos bias the neural encoding of incidental economic decisions

Human decision-making is driven by subjective values assigned to alternative choice options. These valuations are based on reward cues. It is unknown, however, whether complex reward cues, such as brand logos, may bias the neural encoding of subjective value in unrelated decisions. In this functional magnetic resonance imaging (fMRI) study, we subliminally presented brand logos preceding intertemporal choices. We demonstrated that priming biased participants' preferences towards more immediate rewards in the subsequent temporal discounting task. This was associated with modulations of the neural encoding of subjective values of choice options in a network of brain regions, including but not restricted to medial prefrontal cortex. Our findings demonstrate the general susceptibility of the human decision making system to apparently incidental contextual information. We conclude that the brain incorporates seemingly unrelated value information that modifies decision making outside the decision-maker's awareness.

Differential dependence of Pavlovian incentive motivation and instrumental incentive learning processes on dopamine signaling

Here we attempted to clarify the role of dopamine signaling in reward seeking. In Experiment 1, we assessed the effects of the dopamine D(1)/D(2) receptor antagonist flupenthixol (0.5 mg/kg i.p.) on Pavlovian incentive motivation and found that flupenthixol blocked the ability of a conditioned stimulus to enhance both goal approach and instrumental performance (Pavlovian-to-instrumental transfer). In Experiment 2 we assessed the effects of flupenthixol on reward palatability during post-training noncontingent re-exposure to the sucrose reward in either a control 3-h or novel 23-h food-deprived state. Flupenthixol, although effective in blocking the Pavlovian goal approach, was without effect on palatability or the increase in reward palatability induced by the upshift in motivational state. This noncontingent re-exposure provided an opportunity for instrumental incentive learning, the process by which rats encode the value of a reward for use in updating reward-seeking actions. Flupenthixol administered prior to the instrumental incentive learning opportunity did not affect the increase in subsequent off-drug reward-seeking actions induced by that experience. These data suggest that although dopamine signaling is necessary for Pavlovian incentive motivation, it is not necessary for changes in reward experience, or for the instrumental incentive learning process that translates this experience into the incentive value used to drive reward-seeking actions, and provide further evidence that Pavlovian and instrumental incentive learning processes are dissociable.

Dopamine and the Neural “Now”

Rather than view addiction as a disease, Heyman sees it as a choice—one that works like other choices, whereby immediate rewards outshine long-term gains. He rejects neuroscientific explanations of addictive behavior, because he believes they cast it as involuntary or disease-like. I argue that the disease-versus-choice debate creates a false dichotomy: Neuroscience does not have to frame addiction as a disease. Rather, it can help explain how addicts make impulsive choices in the moment and distort appraisal and decision-making habits in the long run. Specifically, the salience of drug-related cues is enhanced by dopamine activity in the ventral striatum, orbitofrontal cortex, and amygdala, due to the intense hedonic impact of repeated drug experiences. Moreover, dopamine-based craving peaks when drug (or alcohol or gambling) rewards become available, in the moment, and this rapid increase in attractiveness preempts rational judgment. Finally, repeated dopamine enhancement modifies brain structures to maximize the appeal of addictive activities, minimize the appeal of competing rewards, and undermine the cognitive capacities necessary to choose between them. I conclude that addiction is not a monolithic state but a recurrent series of choices that permit negotiation, and sometimes cooperation, between immediate and long-range goals.

Wanting and Liking: Observations from the Neuroscience and Psychology Laboratory

Different brain mechanisms seem to mediate wanting and liking for the same reward. This may have implications for the modular nature of mental processes, and for understanding addictions, compulsions, free will and other aspects of desire. A few wanting and liking phenomena are presented here, together with discussion of some of these implications.

'Liking' and 'wanting' food rewards: brain substrates and roles in eating disorders

What brain reward systems mediate motivational 'wanting' and hedonic 'liking' for food rewards? And what roles do those systems play in eating disorders? This article surveys recent findings regarding brain mechanisms of hedonic 'liking', such as the existence of cubic-millimeter hedonic hotspots in nucleus accumbens and ventral pallidum for opioid amplification of sensory pleasure. It also considers brain 'wanting' or incentive salience systems important to appetite, such as mesolimbic dopamine systems and opioid motivation circuits that extend beyond the hedonic hotspots. Finally, it considers some potential ways in which 'wanting' and 'liking' might relate to eating disorders.

A neural computational model of incentive salience

Incentive salience is a motivational property with 'magnet-like' qualities. When attributed to reward-predicting stimuli (cues), incentive salience triggers a pulse of 'wanting' and an individual is pulled toward the cues and reward. A key computational question is how incentive salience is generated during a cue re-encounter, which combines both learning and the state of limbic brain mechanisms. Learning processes, such as temporal-difference models, provide one way for stimuli to acquire cached predictive values of rewards. However, empirical data show that subsequent incentive values are also modulated on the fly by dynamic fluctuation in physiological states, altering cached values in ways requiring additional motivation mechanisms. Dynamic modulation of incentive salience for a Pavlovian conditioned stimulus (CS or cue) occurs during certain states, without necessarily requiring (re)learning about the cue. In some cases, dynamic modulation of cue value occurs during states that are quite novel, never having been experienced before, and even prior to experience of the associated unconditioned reward in the new state. Such cases can include novel drug-induced mesolimbic activation and addictive incentive-sensitization, as well as natural appetite states such as salt appetite. Dynamic enhancement specifically raises the incentive salience of an appropriate CS, without necessarily changing that of other CSs. Here we suggest a new computational model that modulates incentive salience by integrating changing physiological states with prior learning. We support the model with behavioral and neurobiological data from empirical tests that demonstrate dynamic elevations in cue-triggered motivation (involving natural salt appetite, and drug-induced intoxication and sensitization). Our data call for a dynamic model of incentive salience, such as presented here. Computational models can adequately capture fluctuations in cue-triggered 'wanting' only by incorporating modulation of previously learned values by natural appetite and addiction-related states.

Dissecting components of reward: 'liking', 'wanting', and learning

In recent years significant progress has been made delineating the psychological components of reward and their underlying neural mechanisms. Here we briefly highlight findings on three dissociable psychological components of reward: 'liking' (hedonic impact), 'wanting' (incentive salience), and learning (predictive associations and cognitions). A better understanding of the components of reward, and their neurobiological substrates, may help in devising improved treatments for disorders of mood and motivation, ranging from depression to eating disorders, drug addiction, and related compulsive pursuits of rewards.