Dissociable effects of basolateral amygdala lesions on decision making biases in rats when loss or gain is emphasized

Noradrenergic modulation of stress induced catecholamine release: Opposing influence of FG7142 and yohimbine

BACKGROUND

Life stress modulates decision making, particularly in the face of risk, in some cases prompting vulnerable populations to make suboptimal, life-altering choices. In the brain, stress is known to alter the extracellular release of catecholamines in structures such as basolateral amygdala (BLA) and nucleus accumbens (NAc), but the relationship between catecholamines and decision-making behavior under stress has not been systemically explored.

METHODS

We developed an operant touchscreen decision-making task for rats comprising elements of loss aversion and risk seeking behavior. Rats were first injected systemically with an adrenergic alpha 2A-receptor agonist (guanfacine) and antagonist (yohimbine), as well as a partial inverse GABAA agonist, FG 7142, known to induce anxiety and stress related physiological responses in a variety of species, including humans. We then used fiber photometry to monitor NE in the basolateral amygdala (BLA), and DA activity in the nucleus accumbens (NAc) while animals engaged in decision-making and following systemic injections of FG 7142 and yohimbine.

RESULTS

Neither yohimbine nor guanfacine had any impact on decision making strategy but altered motivational state with yohimbine making the animal almost insensitive to the reward outcome. The pharmacological induction of stress with FG 7142 biased the rats decisions towards safety, but this bias shifted toward risk when co-treated with yohimbine. In the BLA and NAc, the FG 7142 altered catecholamine release, with systemic yohimbine producing opposing effects on NE and DA release.

CONCLUSIONS

Stress induced changes in catecholamine release in the BLA and NAc can directly influence loss sensitivity, decisions and motivation, which can be modulated by the alpha 2A adrenoceptor antagonist, yohimbine.

GABAB receptors in prelimbic cortex and basolateral amygdala differentially influence intertemporal decision making and decline with age

The ability to decide adaptively between immediate vs. delayed gratification (intertemporal choice) is critical for well-being and is associated with a range of factors that influence quality of life. In contrast to young adults, many older adults show enhanced preference for delayed gratification; however, the neural mechanisms underlying this age difference in intertemporal choice are largely un-studied. Changes in signaling through GABA_B receptors (GABA_BRs) mediate several age-associated differences in cognitive processes linked to intertemporal choice. The current study used a rat model to determine how GABA_BRs in two brain regions known to regulate intertemporal choice (prelimbic cortex; PrL and basolateral amygdala; BLA) contribute to age differences in this form of decision making in male rats. As in humans, aged rats showed enhanced preference for large, delayed over small, immediate rewards during performance in an intertemporal choice task in operant test chambers. Activation of PrL GABA_BRs via microinfusion of the agonist baclofen increased choice of large, delayed rewards in young adult rats but did not influence choice in aged rats. Conversely, infusion of baclofen into the BLA strongly reduced choice of large, delayed rewards in both young adult and aged rats. Aged rats further showed a significant reduction in expression of GABA_BR1 subunit isoforms in the prefrontal cortex, a discovery that is consonant with the null effect of intra-PrL baclofen on intertemporal choice in aged rats. In contrast, expression of GABA_BR subunits was generally conserved with age in the BLA. Jointly, these findings elucidate a role for GABA_BRs in intertemporal choice and identify fundamental features of brain maturation and aging that mediate an improved ability to delay gratification.

Decision making in Parkinson's disease: An analysis of the studies using the Iowa Gambling Task

In Parkinson's disease (PD) impairments in decision making can occur, in particular because of the tendency toward risky and rewarding options. The Iowa Gambling Task has been widely used to investigate decision processes involving these options. The task assesses the ability to manage risk and to learn from feedback. The present paper aims at critically examining those studies in which this task has been administered to PD patients, in order to understand possible anomalies in patients' decision processes and which variables are responsible for that. A meta‐analysis has been conducted as well. Features of the task, sociodemographic and clinical aspects (including daily drugs intake), cognitive conditions and emotional disorders of the patients have been taken into account. Neural correlates of decision‐making competences were considered. It emerged that PD patients show a trend of preference toward risky choices, probably due to an impairment in anticipating the unrewarding consequences or to an insensitiveness to punishment. The possible role played by dopamine medications in decision making under uncertain conditions, affecting basal ganglia and structures involved in the limbic loop, was discussed. Attention has been focused on some aspects that need to be investigated in further research, in order to delve into this issue and promote patients' quality of life.

Advances in understanding meso-cortico-limbic-striatal systems mediating risky reward seeking

The risk of an aversive consequence occurring as the result of a reward-seeking action can have a profound effect on subsequent behavior. Such aversive events can be described as punishers, as they decrease the probability that the same action will be produced again in the future and increase the exploration of less risky alternatives. Punishment can involve the omission of an expected rewarding event ("negative" punishment) or the addition of an unpleasant event ("positive" punishment). Although many individuals adaptively navigate situations associated with the risk of negative or positive punishment, those suffering from substance use disorders or behavioral addictions tend to be less able to curtail addictive behaviors despite the aversive consequences associated with them. Here, we discuss the psychological processes underpinning reward seeking despite the risk of negative and positive punishment and consider how behavioral assays in animals have been employed to provide insights into the neural mechanisms underlying addictive disorders. We then review the critical contributions of dopamine signaling to punishment learning and risky reward seeking, and address the roles of interconnected ventral striatal, cortical, and amygdala regions to these processes. We conclude by discussing the ample opportunities for future study to clarify critical gaps in the literature, particularly as related to delineating neural contributions to distinct phases of the risky decision-making process.

Computations and Connectivity Underlying Aversive Counterfactuals

Background: Mentally simulating counterfactuals (scenarios that have not actually occurred) is a sophisticated human cognitive function underlying creativity, planning, and daydreaming. One example is the "would you rather" game, in which forced choices are made between outlandish negative counterfactuals. Materials and Methods: We measured behavioral and neural correlates while participants made "would you rather" choices framed as approaching or avoiding aversive counterfactual scenarios (e.g., illnesses, car accidents). Results: We found in two independent cohorts that participants were highly susceptible to framing effects when making these decisions, taking significantly longer to respond to approach frames compared with avoidance. Brain imaging showed that choices to approach and avoid resulted in a pattern of activation consistent with a network associated with responding to aversive stimuli, identified via a coordinate-based meta-analysis of 238 studies. Bayesian graph connectivity analysis showed that network connectivity differed by choice frame, with significantly stronger connectivity for approach choices compared with avoidance choices among primarily limbic nodes (putamen, insula, caudate, and amygdala). Computational modeling of behavior revealed that approach frames led to significantly longer nondecision times, increased evidence required to make decisions, and faster evidence accumulation than avoidance frames. Stronger network connectivity between corticostriatal and limbic regions was associated with rate of evidence accumulation and length of nondecision time during approach choices. For avoidance choices, prefrontal connectivity was related to nondecision time. Conclusions: These results suggest that "would you rather" decisions about aversive counterfactuals differentially recruit limbic circuit connectivity based on choice frame. Impact statement We measured brain connectivity and latent cognitive variables underlying aversive counterfactual choices. We found a replicable reaction time effect whereby approach decisions were slower than avoidance decisions. Computational modeling identified that the latent cognitive variable of evidence accumulation was related to strength of connectivity between corticostriatal and limbic nodes during approach decisions. Multidimensional scaling (MDS) and clustering revealed a three-dimensional choice structure that differed between individuals, and between approach and avoidance choices within individuals. Our results suggest that cognitive evaluations of aversive counterfactuals involve flexible representations that can be altered by choice framing. These findings have broad implications for prospective decision making.

Translating concepts of risk and loss in rodent models of gambling and the limitations for clinical applications

Gambling involves placing something of value at risk in exchange for the opportunity to potentially gain something of greater value in return. A variety of gambling paradigms have been designed to study the maladaptive decision-making that underlies problematic gambling. Central to these gambling models are the definitions of "risk" and "loss", especially when translating the results from rodent studies to clinical applications. Risk and loss are not mutually exclusive but rather share some overlap. With careful interpretation and consideration of the limitations of these behavioral paradigms, results from rodent models may provide insights into the neurobiology of risky decision-making that leads to problematic gambling in humans.

Understanding Addiction Using Animal Models

Drug addiction is a neuropsychiatric disorder with grave personal consequences that has an extraordinary global economic impact. Despite decades of research, the options available to treat addiction are often ineffective because our rudimentary understanding of drug-induced pathology in brain circuits and synaptic physiology inhibits the rational design of successful therapies. This understanding will arise first from animal models of addiction where experimentation at the level of circuits and molecular biology is possible. We will review the most common preclinical models of addictive behavior and discuss the advantages and disadvantages of each. This includes non-contingent models in which animals are passively exposed to rewarding substances, as well as widely used contingent models such as drug self-administration and relapse. For the latter, we elaborate on the different ways of mimicking craving and relapse, which include using acute stress, drug administration or exposure to cues and contexts previously paired with drug self-administration. We further describe paradigms where drug-taking is challenged by alternative rewards, such as appetitive foods or social interaction. In an attempt to better model the individual vulnerability to drug abuse that characterizes human addiction, the field has also established preclinical paradigms in which drug-induced behaviors are ranked by various criteria of drug use in the presence of negative consequences. Separation of more vulnerable animals according to these criteria, along with other innate predispositions including goal- or sign-tracking, sensation-seeking behavior or impulsivity, has established individual genetic susceptibilities to developing drug addiction and relapse vulnerability. We further examine current models of behavioral addictions such as gambling, a disorder included in the DSM-5, and exercise, mentioned in the DSM-5 but not included yet due to insufficient peer-reviewed evidence. Finally, after reviewing the face validity of the aforementioned models, we consider the most common standardized tests used by pharmaceutical companies to assess the addictive potential of a drug during clinical trials.

Lesions of the rat basolateral amygdala reduce the behavioral response to ultrasonic vocalizations

Rats emit vocalizations in the ultrasonic range (ultrasonic vocalizations; USVs), of which 50-kHz USVs could communicate positive affective states and induce approach behavior in conspecifics, whereas 22-kHz USVs might signal negative affective states and potential threats. Listening to 50-kHz USVs can be rewarding, but it is unknown which brain mechanisms are responsible for the assignment of reinforcing value to 50-kHz USVs . The behavioral responses induced by listening to 22-kHz USVs are heterogeneous and need further characterization. The amygdala is a region relevant for social perception, behavior and reward. Here, we tested the hypothesis that the basolateral amygdala (BLA) plays a causal role in motivating behavioral responses to 50-kHz and 22-kHz USVs. Rats with lesions of the BLA or sham lesions were repeatedly exposed to playback of either 50-kHz or 22-kHz USVs in a radial maze. Compared to sham rats, BLA-lesioned rats spent less time in the arms close to the USV speaker during playback of both 50-kHz or 22-kHz USVs. This difference in behavior was not due to impaired motor or general auditory abilities, indicating that BLA lesions selectively reduced the responsiveness to stimuli with social significance. This finding provides further support for the hypothesis that the BLA plays an important role in motivating approach behavior to social reinforcers.

Investigating the influence of 'losses disguised as wins' on decision making and motivation in rats

Multiline slot machines encourage continued play through 'losses disguised as wins' (LDWs), outcomes in which the money returned is less than that wagered. Individuals with gambling problems may be susceptible to this game feature. The cognitive and neurobiological mechanisms through which LDWs act are unknown. In a novel rat operant task, animals chose between a 'certain' lever, which always delivered two sugar pellets, or an 'uncertain' lever, resulting in four sugar pellets on 50% of trials. LDWs were then introduced as a return of three sugar pellets on 30-40% of uncertain rewarded trials. For half the rats, winning outcomes were paired with audiovisual feedback (cues). In a second study, the basolateral amygdala (BLA) was inactivated during initial presentation of LDWs. While LDWs shifted most rats' choice toward the certain lever, a subgroup of LDW vulnerable rats continued to choose the uncertain option, when the reward rate diminished. This profile of LDW vulnerability was reproduced after inactivating the BLA. Persistent choice of uncertain outcomes despite lower reward rates may reflect impaired functioning within the BLA. Future work using this model may provide insight into the neurobiological mechanisms contributing to the motivational properties of LDWs and their contribution to problematic gambling.

Exploring preferences for variable delays over fixed delays to high-value food rewards as a model of food-seeking behaviours in humans

Foraging and operant models suggest that animals will tolerate uncertainty or risk to obtain food quickly. In modern food environments, sustained access to quick energy-dense foods can promote weight gain. Here, we used a discrete-choice procedure to examine peoples' decisions about when next to eat high-value, palatable food rewards, probabilistically delivered immediately or following longer delays. In Experiment 1, moderately hungry young females showed consistent preferences for a variable delay option that delivered food rewards immediately or following long delays over a fixed delay option that delivered the same rewards following intermediate delays. These preferences were stronger in females with higher BMIs compared with lower BMIs, suggesting that quick food can enhance the value of uncertain or 'risky' food-seeking strategies in individuals vulnerable to future weight gain. In Experiment 2, prior exposure to a subtle and not easily identifiable food aroma increased selections of the variable delay option following delayed food rewards in a mixed sample of male and female adults, providing preliminary evidence that food cues can sustain uncertain food-seeking strategies. These data highlight a working hypothesis that the rapid delivery and consumption of food rewards, and food cues, can increase risk-tolerance in the food-seeking behaviours of individuals who are vulnerable to weight gain. This article is part of the theme issue 'Risk taking and impulsive behaviour: fundamental discoveries, theoretical perspectives and clinical implications'.

Review: brain neurobiology of gambling disorder based on rodent models

Different literature reviews of gambling disorder (GD) neurobiology have been focused on human studies, others have focused on rodents, and others combined human and rodent studies. The main question of this review was: which are the main neurotransmitters systems and brain structures relevant for GD based on recent rodent studies? This work aims to review the experimental findings regarding the rodent´s neurobiology of GD. A search in the Pub Med database was set (October 2012-October 2017) and 162 references were obtained. After screening, 121 references were excluded, and only 41 references remained from the initial output. More, other 25 references were added to complement (introduction section, neuroanatomical descriptions) the principal part of the work. At the end, a total of 66 references remained for the review. The main conclusions are: 1) according to studies that used noninvasive methods for drug administration, some of the neurotransmitters and receptors involved in behaviors related to GD are: muscarinic, N-methyl-D-aspartate (NMDA), cannabinoid receptor 1 (CB₁), cannabinoid receptor 2 (CB₂), dopamine 2 receptor (D₂), dopamine 3 receptor (D₃), and dopamine 4 receptor (D₄); 2) moreover, there are other neurotransmitters and receptors involved in GD based on studies that use invasive methods of drug administration (eg, brain microinjection); example of these are: serotonin 1A receptor (5-HT_1A), noradrenaline receptors, gamma-aminobutyric acid receptor A (GABA_A), and gamma-aminobutyric acid receptor B (GABA_B); 3) different brain structures are relevant to behaviors linked to GD, like: amygdala (including basolateral amygdala (BLA)), anterior cingulate cortex (ACC), hippocampus, infralimbic area, insular cortex (anterior and rostral agranular), nucleus accumbens (NAc), olfactory tubercle (island of Calleja), orbitofrontal cortex (OFC), medial prefrontal cortex (mPFC), prefrontal cortex (PFC) - subcortical network, striatum (ventral) and the subthalamic nucleus (STN); and 4) the search for GD treatments should consider this diversity of receptor/neurotransmitter systems and brain areas.

Reinforcement learning models of risky choice and the promotion of risk-taking by losses disguised as wins in rats

Risky decisions are inherently characterized by the potential to receive gains or incur losses, and these outcomes have distinct effects on subsequent decision-making. One important factor is that individuals engage in loss-chasing, in which the reception of a loss is followed by relatively increased risk-taking. Unfortunately, the mechanisms of loss-chasing are poorly understood, despite the potential importance for understanding pathological choice behavior. The goal of the present experiment was to illuminate the mechanisms governing individual differences in loss-chasing and risky-choice behaviors. Rats chose between a low-uncertainty outcome that always delivered a variable amount of reward and a high-uncertainty outcome that probabilistically delivered reward. Loss-processing and loss-chasing were assessed in the context of losses disguised as wins (LDWs), which are loss outcomes that are presented along with gain-related stimuli. LDWs have been suggested to interfere with adaptive decision-making in humans and thus potentially increase loss-making. Here, the rats presented with LDWs were riskier, in that they made more choices for the high-uncertainty outcome. A series of nonlinear models were fit to individual rats' data to elucidate the possible psychological mechanisms that best account for individual differences in high-uncertainty choices and loss-chasing behaviors. The models suggested that the rats presented with LDWs were more prone to showing a stay bias following high-uncertainty outcomes compared to rats not presented with LDWs. These results collectively suggest that LDWs acquire conditioned reinforcement properties that encourage continued risk-taking and increase loss-chasing following previous high-risk decisions. (PsycINFO Database Record

Uncertainty exposure causes behavioural sensitization and increases risky decision-making in male rats: toward modelling gambling disorder

BACKGROUND

An animal model of gambling disorder, previously known as pathological gambling, could advance our understanding of the disorder and help with treatment development. We hypothesized that repeated exposure to uncertainty during gambling induces behavioural and dopamine (DA) sensitization - similar to chronic exposure to drugs of abuse. Uncertainty exposure (UE) may also increase risky decision-making in an animal model of gambling disorder.

METHODS

Male Sprague Dawley rats received 56 UE sessions, during which animals responded for saccharin according to an unpredictable, variable ratio schedule of reinforcement (VR group). Control animals responded on a predictable, fixed ratio schedule (FR group). Rats yoked to receive unpredictable reward were also included (Y group). Animals were then tested on the Rat Gambling Task (rGT), an analogue of the Iowa Gambling Task, to measure decision-making.

RESULTS

Compared with the FR group, the VR and Y groups experienced a greater locomotor response following administration of amphetamine. On the rGT, the FR and Y groups preferred the advantageous options over the risky, disadvantageous options throughout testing (40 sessions). However, rats in the VR group did not have a significant preference for the advantageous options during sessions 20-40. Amphetamine had a small, but significant, effect on decision-making only in the VR group. After rGT testing, only the VR group showed greater hyperactivity following administration of amphetamine compared with the FR group.

LIMITATIONS

Reward uncertainty was the only gambling feature modelled.

CONCLUSION

Actively responding for uncertain reward likely sensitized the DA system and impaired the ability to make optimal decisions, modelling some aspects of gambling disorder.

Optogenetic Inhibition Reveals Distinct Roles for Basolateral Amygdala Activity at Discrete Time Points during Risky Decision Making

Decision making is a multifaceted process, consisting of several distinct phases that likely require different cognitive operations. Previous work showed that the basolateral amygdala (BLA) is a critical substrate for decision making involving risk of punishment; however, it is unclear how the BLA is recruited at different stages of the decision process. To this end, the current study used optogenetics to inhibit the BLA during specific task phases in a model of risky decision making (risky decision-making task) in which rats choose between a small, "safe" reward and a large reward accompanied by varying probabilities of footshock punishment. Male Long-Evans rats received intra-BLA microinjections of viral vectors carrying either halorhodopsin (eNpHR3.0-mCherry) or mCherry alone (control) followed by optic fiber implants and were trained in the risky decision-making task. Laser delivery during the task occurred during intertrial interval, deliberation, or reward outcome phases, the latter of which was further divided into the three possible outcomes (small, safe; large, unpunished; large, punished). Inhibition of the BLA selectively during the deliberation phase decreased choice of the large, risky outcome (decreased risky choice). In contrast, BLA inhibition selectively during delivery of the large, punished outcome increased risky choice. Inhibition had no effect during the other phases, nor did laser delivery affect performance in control rats. Collectively, these data indicate that the BLA can either inhibit or promote choice of risky options, depending on the phase of the decision process in which it is active.SIGNIFICANCE STATEMENT To date, most behavioral neuroscience research on neural mechanisms of decision making has used techniques that preclude assessment of distinct phases of the decision process. Here we show that optogenetic inhibition of the BLA has opposite effects on choice behavior in a rat model of risky decision making, depending on the phase in which inhibition occurs. BLA inhibition during a period of deliberation between small, safe and large, risky outcomes decreased risky choice. In contrast, BLA inhibition during receipt of the large, punished outcome increased risky choice. These findings highlight the importance of temporally targeted approaches to understand neural substrates underlying complex cognitive processes. More importantly, they reveal novel information about dynamic BLA modulation of risky choice.

Deciphering Decision Making: Variation in Animal Models of Effort- and Uncertainty-Based Choice Reveals Distinct Neural Circuitries Underlying Core Cognitive Processes

Maladaptive decision-making is increasingly recognized to play a significant role in numerous psychiatric disorders, such that therapeutics capable of ameliorating core impairments in judgment may be beneficial in a range of patient populations. The field of "decision neuroscience" is therefore in its ascendancy, with researchers from diverse fields bringing their expertise to bear on this complex and fascinating problem. In addition to the advances in neuroimaging and computational neuroscience that contribute enormously to this area, an increase in the complexity and sophistication of behavioral paradigms designed for nonhuman laboratory animals has also had a significant impact on researchers' ability to test the causal nature of hypotheses pertaining to the neural circuitry underlying the choice process. Multiple such decision-making assays have been developed to investigate the neural and neurochemical bases of different types of cost/benefit decisions. However, what may seem like relatively trivial variation in behavioral methodologies can actually result in recruitment of distinct cognitive mechanisms, and alter the neurobiological processes that regulate choice. Here we focus on two areas of particular interest, namely, decisions that involve an assessment of uncertainty or effort, and compare some of the most prominent behavioral paradigms that have been used to investigate these processes in laboratory rodents. We illustrate how an appreciation of the diversity in the nature of these tasks can lead to important insights into the circumstances under which different neural regions make critical contributions to decision making.

Risk-preferring rats make worse decisions and show increased incubation of craving after cocaine self-administration

Maladaptive decision-making may play an integral role in the development and maintenance of an addiction. Substance-dependent individuals make riskier choices on the Iowa Gambling Task, and these deficits persist during withdrawal and are predictive of relapse. However, it is unclear from clinical studies whether this cognitive impairment is a cause or consequence of drug use. We trained male Long-Evans rats on the rat Gambling Task, a rodent analogue of the Iowa Gambling Task, to determine how choice preference influenced, and was influenced by, cocaine self-administration, withdrawal and incubation of craving. Rats that exhibited a preference for the risky, disadvantageous options at baseline were uniquely and adversely affected by cocaine self-administration. Risky choice was exacerbated in these rats when decision-making was assessed during the same diurnal period as cocaine self-administration, whereas the choice pattern of optimal decision-makers was unaffected. This decision-making deficit was maintained during 30 days of withdrawal and correlated with greater cue-induced incubation of craving. Risk-preferring rats also made more drug-seeking responses during cocaine self-administration. These data demonstrate that poor decision-making prior to contact with addictive drugs is associated with a pro-addictive behavioural phenotype, characterized by further increased risky choice and heightened responding for drug both during cocaine self-administration and withdrawal. Such findings indicate that the elevated risky decision-making observed in substance-dependent populations is not merely circumstantial, but makes an important contribution to addiction vulnerability and severity that can now be effectively modelled in laboratory rats.

Neural responses to negative outcomes predict success in community-based substance use treatment

BACKGROUND AND AIMS

Patterns of brain activation have demonstrated promise as prognostic indicators in substance dependent individuals (SDIs) but have not yet been explored in SDIs typical of community-based treatment settings.

DESIGN

Prospective clinical outcome design, evaluating baseline functional magnetic resonance imaging data from the Balloon Analogue Risk Task (BART) as a predictor of 3-month substance use treatment outcomes.

SETTING

Community-based substance use programs in Bloomington, Indiana, USA.

PARTICIPANTS

Twenty-three SDIs (17 male, aged 18-43 years) in an intensive outpatient or residential treatment program; abstinent 1-4 weeks at baseline.

MEASUREMENTS

Event-related brain response, BART performance and self-report scores at treatment onset, substance use outcome measure (based on days of use).

FINDINGS

Using voxel-level predictive modeling and leave-one-out cross-validation, an elevated response to unexpected negative feedback in bilateral amygdala and anterior hippocampus (Amyg/aHipp) at baseline successfully predicted greater substance use during the 3-month study interval (P ≤ 0.006, cluster-corrected). This effect was robust to inclusion of significant non-brain-based covariates. A larger response to negative feedback in bilateral Amyg/aHipp was also associated with faster reward-seeking responses after negative feedback (r₍₂₃₎  = -0.544, P = 0.007; r₍₂₃₎  = -0.588, P = 0.003). A model including Amyg/aHipp activation, faster reward-seeking after negative feedback and significant self-report scores accounted for 45% of the variance in substance use outcomes in our sample.

CONCLUSIONS

An elevated response to unexpected negative feedback in bilateral amygdala and anterior hippocampus (Amyg/aHipp) appears to predict relapse to substance use in people attending community-based treatment.

Research Domain Criteria versus DSM V: How does this debate affect attempts to model corticostriatal dysfunction in animals?

For decades, the nosology of mental illness has been based largely upon the descriptions in the Diagnostic and Statistical Manual of the American Psychiatric Association (DSM). A recent challenge to the DSM approach to psychiatric nosology from the National Institute on Mental Health (USA) defines Research Domain Criteria (RDoC) as an alternative. For RDoC, psychiatric illnesses are not defined as discrete categories, but instead as specific behavioral dysfunctions irrespective of DSM diagnostic categories. This approach was driven by two primary weaknesses noted in the DSM: (1) the same symptoms occur in very different disease states; and (2) DSM criteria lack grounding in the underlying biological causes of mental illness. RDoC intends to ground psychiatric nosology in those underlying mechanisms. This review addresses the suitability of RDoC vs. DSM from the view of modeling mental illness in animals. A consideration of all types of psychiatric dysfunction is beyond the scope of this review, which will focus on models of conditions associated with frontostriatal dysfunction.

Chronic D2/3 agonist ropinirole treatment increases preference for uncertainty in rats regardless of baseline choice patterns

D_2/3 receptor agonists are effective treatments for Parkinson's disease (PD), but can precipitate impulse control disorders (ICDs) including gambling disorder (GD). The neurobiological mechanisms underlying this devastating side-effect of dopamine agonist replacement therapy (DRT), and any dependence on the dopamine depletion caused by PD, are unclear. It is also unclear whether previous biases towards risk or uncertainty are a risk factor for developing these ICDs. We investigated whether chronic D_2/3 agonist administration (5 mg/kg/day ropinirole for 28 days) altered performance of a rat model of gambling-like behaviour, the rodent betting task (rBT), and examined if baseline behaviour predicted this behavioural change. The rBT captures individual differences in subjective preference for uncertain outcomes: animals choose between guaranteed or probabilistic reinforcement of equal expected value. Chronic ropinirole dramatically increased selection of the uncertain option in two-thirds of animals, regardless of baseline preferences. The effect on choice in the rBT was replicated in a dorsolateral striatal 6-hydroxydopamine (6-OHDA) rat model of early PD. These studies are the first to look at individual differences in response to chronic, rather than pulsatile, dosing of DRT in a rodent model of gambling behaviour. These findings suggest that DRT-induced PG may stem from increases in subjective valuation of uncertainty. Such symptoms likely arise because of changes in dopaminergic striatal signalling caused by DRT rather than from an interaction between pre-morbid behaviours or PD itself.

Inactivation of the orbitofrontal cortex reduces irrational choice on a rodent Betting Task

Cognitive biases may play a significant role in disorders of decision making such as pathological gambling and addiction. Understanding the neurobiology of these biases could lead to more effective pharmacological and therapeutic treatments for disorders in which aberrant decision making is prominent. The rodent Betting Task (rBT) was designed to measure one commonly observed decision-making heuristic in rodents, namely "escalation of commitment" in which subjects become more risk averse as the stakes increase, even if the odds of success remain constant. In the rodent task, the animal is presented with a choice between two options of equivalent expected value, such that reward on one option is guaranteed while the other has a 50% chance of double the prize or nothing. Past work has shown that a subset of animals (termed wager sensitive) adopt an irrationally risk-averse choice preference in which they shift their choice away from the uncertain option as the bet size grows larger. In the current study, the orbitofrontal (OFC), prelimbic (PrL), and infralimbic cortex (IL) were inactivated to evaluate the contributions made by these regions to choice behavior on the rBT. Inactivation of the OFC (but not the IL or the PrL) selectively ameliorated the risk-averse choice pattern characteristic of wager-sensitive animals. This finding suggests that the OFC may have a relatively unique role in promoting this type of non-normative decision-making under uncertainty, an effect that is potentially related to its role in representing the subjective value of reinforcing outcomes.

The basolateral amygdala in reward learning and addiction

Sophisticated behavioral paradigms partnered with the emergence of increasingly selective techniques to target the basolateral amygdala (BLA) have resulted in an enhanced understanding of the role of this nucleus in learning and using reward information. Due to the wide variety of behavioral approaches many questions remain on the circumscribed role of BLA in appetitive behavior. In this review, we integrate conclusions of BLA function in reward-related behavior using traditional interference techniques (lesion, pharmacological inactivation) with those using newer methodological approaches in experimental animals that allow in vivo manipulation of cell type-specific populations and neural recordings. Secondly, from a review of appetitive behavioral tasks in rodents and monkeys and recent computational models of reward procurement, we derive evidence for BLA as a neural integrator of reward value, history, and cost parameters. Taken together, BLA codes specific and temporally dynamic outcome representations in a distributed network to orchestrate adaptive responses. We provide evidence that experiences with opiates and psychostimulants alter these outcome representations in BLA, resulting in long-term modified action.

Addiction-related genes in gambling disorders: new insights from parallel human and pre-clinical models

Neurobiological research supports the characterization of disordered gambling (DG) as a behavioral addiction. Recently, an animal model of gambling behavior was developed (rat gambling task, rGT), expanding the available tools to investigate DG neurobiology. We investigated whether rGT performance and associated risk gene expression in the rat's brain could provide cross-translational understanding of the neuromolecular mechanisms of addiction in DG. We genotyped tagSNPs (single-nucleotide polymorphisms) in 38 addiction-related genes in 400 DG and 345 non-DG subjects. Genes with P<0.1 in the human association analyses were selected to be investigated in the animal arm to determine whether their mRNA expression in rats was associated with the rat's performance on the rGT. In humans, DG was significantly associated with tagSNPs in DRD3 (rs167771) and CAMK2D (rs3815072). Our results suggest that age and gender might moderate the association between CAMK2D and DG. Moderation effects could not be investigated due to sample power. In the animal arm, only the association between rGT performance and Drd3 expression remained significant after Bonferroni correction for 59 brain regions. As male rats were used, gender effects could not be investigated. Our results corroborate previous findings reporting the involvement of DRD3 receptor in addictions. To our knowledge, the use of human genetics, pre-clinical models and gene expression as a cross-translation paradigm has not previously been attempted in the field of addictions. The cross-validation of human findings in animal models is crucial for improving the translation of basic research into clinical treatments, which could accelerate neurobiological and pharmacological investigations in addictions.

Differential Involvement of the Agranular vs Granular Insular Cortex in the Acquisition and Performance of Choice Behavior in a Rodent Gambling Task

Substance-related and addictive disorders, in particular gambling disorder, are known to be associated with risky decision-making behavior. Several neuroimaging studies have identified the involvement of the insular cortex in decision-making under risk. However, the extent of this involvement remains unclear and the specific contributions of two distinct insular subregions, the rostral agranular (RAIC) and the caudal granular (CGIC), have yet to be examined. Animals were trained to perform a rat gambling task (rGT), in which subjects chose between four options that differed in the magnitude and probability of rewards and penalties. In order to address the roles of the RAIC and CGIC in established choice behavior, pharmacological inactivations of these two subregions via local infusions of GABA receptor agonists were performed following 30 rGT training sessions. The contribution made by the RAIC or CGIC to the acquisition of choice behavior was also determined by lesioning these areas before behavioral training. Inactivation of the RAIC, but not of the CGIC, shifted rats' preference toward options with greater reward frequency and lower punishment. Before rGT acquisition, lesions of the RAIC, but not the CGIC, likewise resulted in a higher preference for options with greater reward frequency and lower punishment, and this persisted throughout the 30 training sessions. Our results provide confirmation of the involvement of the RAIC in rGT choice behavior and suggest that the RAIC may mediate detrimental risky decision-making behavior, such as that associated with addiction and gambling disorder.

Prefrontal Cortical Inactivations Decrease Willingness to Expend Cognitive Effort on a Rodent Cost/Benefit Decision-Making Task

Personal success often necessitates expending greater effort for greater reward but, equally important, also requires judicious use of our limited cognitive resources (e.g., attention). Previous animal models have shown that the prelimbic (PL) and infralimbic (IL) regions of the prefrontal cortex (PFC) are not involved in (physical) effort-based choice, whereas human studies have demonstrated PFC contributions to (mental) effort. Here, we utilize the rat Cognitive Effort Task (rCET) to probe PFC's role in effort-based decision making. In the rCET, animals can choose either an easy trial, where the attentional demand is low but the reward (sugar) is small or a difficult trial on which both the attentional demand and reward are greater. Temporary inactivation of PL and IL decreased all animals' willingness to expend mental effort and increased animals' distractibility; PL inactivations more substantially affected performance (i.e., attention), whereas IL inactivations increased motor impulsivity. These data imply that the PFC contributes to attentional resources, and when these resources are diminished, animals shift their choice (via other brain regions) accordingly. Thus, one novel therapeutic approach to deficits in effort expenditure may be to focus on the resources that such decision making requires, rather than the decision-making process per se.

Translational Models of Gambling-Related Decision-Making

Gambling is a harmless, recreational pastime that is ubiquitous across cultures. However, for some, gambling becomes a maladaptive and compulsive, and this syndrome is conceptualized as a behavioural addiction. Laboratory models that capture the key cognitive processes involved in gambling behaviour, and that can be translated across species, have the potential to make an important contribution to both decision neuroscience and the study of addictive disorders. The Iowa gambling task has been widely used to assess human decision-making under uncertainty, and this paradigm can be successfully modelled in rodents. Similar neurobiological processes underpin choice behaviour in humans and rats, and thus, a preference for the disadvantageous "high-risk, high-reward" options may reflect meaningful vulnerability for mental health problems. However, the choice behaviour operationalized by these tasks does not necessarily approximate the vulnerability to gambling disorder (GD) per se. We consider a number of psychological challenges that apply to modelling gambling in a translational way, and evaluate the success of the existing models. Heterogeneity in the structure of gambling games, as well as in the motivations of individuals with GD, is highlighted. The potential issues with extrapolating too directly from established animal models of drug dependency are discussed, as are the inherent difficulties in validating animal models of GD in the absence of any approved treatments for GD. Further advances in modelling the cognitive biases endemic in human decision-making, which appear to be exacerbated in GD, may be a promising line of research.