Cognitive judgment bias in the psychostimulant-induced model of mania in rats

Association of Polymorphism within the Putative miRNA Target Site in the 3'UTR Region of the DRD2 Gene with Neuroticism in Patients with Substance Use Disorder

The study aims at looking into associations between the polymorphism rs6276 that occurs in the putative miRNA target site in the 3'UTR region of the DRD2 gene in patients with substance use disorder (SUD) comorbid with a maniacal syndrome (SUD MANIA). In our study, we did not state any essential difference in DRD2 rs6276 genotype frequencies in the studied samples of SUD MANIA, SUD, and control subjects. A significant result was found for the SUD MANIA group vs. SUD vs. controls on the Neuroticism Scale of NEO FFI test, and DRD2 rs6276 (p = 0.0320) accounted for 1.7% of the variance. The G/G homozygous variants were linked with lower results on the neuroticism scale in the SUD MANIA group because G/G alleles may serve a protective role in the expression of neuroticism in patients with SUD MANIA. So far, there have been no data in the literature on the relationship between the miRSNP rs6276 region in the DRD2 gene and neuroticism (personal traits) in patients with a diagnosis of substance use disorder comorbid with the affective, maniacal type disturbances related to SUD. This is the first report on this topic.

Application of Cognitive Bias Testing in Neuropsychiatric Disorders: A Mini-Review Based on Animal Studies

Cognitive biases can arise from cognitive processing under affective states and reflect the impact of emotion on cognition. In animal studies, the existing methods for detecting animal emotional state are still relatively limited, and cognitive bias test has gradually become an important supplement. In recent years, its effectiveness in animal research related to neuropsychiatric disorders has been widely verified. Some studies have found that cognitive bias test is more sensitive than traditional test methods such as forced swimming test and sucrose preference test in detecting emotional state. Therefore, it has great potential to become an important tool to measure the influence of neuropsychiatric disorder-associated emotions on cognitive processing. Moreover, it also can be used in early drug screening to effectively assess the potential effects or side effects of drugs on affective state prior to clinical trials. In this mini-review, we summarize the application of cognitive bias tests in animal models of neuropsychiatric disorders such as depression, anxiety, bipolar disorder, and pain. We also discussed its critical value in the identification of neuropsychiatric disorders and the validation of therapeutic approaches.

A Behavioural Assay to Investigate Judgment Bias in Zebrafish

In this protocol, we describe for the first time a judgment bias paradigm to phenotype the way zebrafish assess ambiguous stimuli. We have developed and validated a protocol for a judgment bias test based on a Go/No-go task, and performed using a half radial maze. After a habituation phase, fish are trained to discriminate between two reference arms [positive (P) and negative (N)]. For this purpose, they experience a positive event (food reward in P), when presented with a specific location/color cue, and a negative event (chasing with net in N), when presented with a different location/color cue. Acquisition of the discrimination learning between P and N is revealed by the latencies to enter the experimental arms of the behavioral maze being significantly lower for the P arm than for the N arm. Once zebrafish are able to discriminate between P and N arms, their latency to enter other maze arms spatially located between P and N [(Near Positive (NP), Ambiguous (A) = half-way between P and N, and Near Negative (NN)] is analyzed. Latencies (L) to enter NP, A and NN maze arms are interpreted as indicating the individual expectancy to experience a reward/punishment on each of them. A judgment bias score (JBS) is calculated from the latencies to enter the P, N, and A arms for each fish [JBS = (LA-LP)*100/(LN-LP)], based on which fish can be classified into an optimistic/pessimistic axis. A JBS below 50 indicates that fish perceive the ambiguous stimulus as a positive one (optimistic bias), while JBS above 50 indicates that fish perceive the ambiguous stimulus as a negative one (pessimistic bias). However, for classification criteria, it could be advantageous to use the method of selecting extreme phenotypes (e.g., upper and lower quartiles of the JBS), since JBS in zebrafish falls into a bimodal distribution (unpublished data). Therefore, this protocol provides a unique, inexpensive, and effective alternative to other methods of measuring affective states in zebrafish that might be of great interest to a broad target audience and have a large number of applications. Graphic abstract: Flow chart of the judgment bias protocol in zebrafish.

Reinforcement-based cognitive biases as vulnerability factors in alcohol addiction: From humans to animal models

Alcohol use disorder (AUD) is one of the most common, but still poorly treated, psychiatric conditions. Developing new treatments requires a better understanding of the aetiology of symptoms and evaluation of novel therapeutic targets in preclinical studies. Recent developments in our understanding of the reinforcement-based cognitive biases (RBCBs) that contribute to the development of AUD and its treatment offer new opportunities for both clinical and preclinical research. In this review, we first briefly describe psychological and cognitive theories that involve various aspects of reinforcement sensitivity in the development, maintenance, and recurrence of alcohol addiction. Furthermore, in separate sections, we describe studies investigating RBCBs and their neural, neurochemical, and pharmacological correlates, and we discuss possible interactions between RBCBs and trajectories of AUD. Finally, we describe how recent translational studies using state-of-the-art animal models can facilitate our understanding of the role of reinforcement sensitivity and RBCBs in various aspects of AUD.

Measuring mania-like elevated mood through amphetamine-induced 50-kHz ultrasonic vocalizations in rats

Rats emit 50-kHz ultrasonic vocalizations (USV) in appetitive situations, reflecting a positive affective state. Particularly high rates of 50-kHz USV are elicited by the psychostimulant d-amphetamine. Exaggerated 50-kHz USV emission evoked by d-amphetamine is modulated by dopamine, noradrenaline and 5-hydroxytyrptamine receptor ligands and inhibited by the mood stabilizer lithium, the gold standard anti-manic drug for treating bipolar disorder. This indicates that exaggerated 50-kHz USV emission can serve as a reliable and valid measure for assessing mania-like elevated mood in rats with sufficient translational power for gaining a better understanding of relevant pathophysiological mechanisms and the identification of new therapeutic targets. The improved capacity to study the effects of anti-manic pharmacological interventions on a broader range of behaviours by including exaggerated 50-kHz USV emission as preclinical outcome measure complementary to locomotor hyperactivity will refine rodent models for mania.

The relationship between monoaminergic gene expression, learning, and optimism in red junglefowl chicks

Intra-species cognitive variation is commonly observed, but explanations for why individuals within a species differ in cognition are still understudied and not yet clear. Cognitive processes are likely influenced by genetic differences, with genes in the monoaminergic systems predicted to be important. To explore the potential role of these genes in association with individual variation in cognition, we exposed red junglefowl (Gallus gallus) chicks to behavioural assays measuring variation in learning (discriminative learning, reversal learning, and cognitive flexibility) and optimism (measured in a cognitive judgement bias test). Following this, we analysed prefrontal cortex gene expression of several dopaminergic and serotonergic genes in these chicks. Of our explored genes, serotonin receptor genes 5HT2A and 5HT2B, and dopaminergic receptor gene DRD1 were associated with measured behaviour. Chicks that had higher 5HT2A were less flexible in the reversal learning task, and chicks with higher 5HT2B also tended to be less cognitively flexible. Additionally, chicks with higher DRD1 were more optimistic, whilst chicks with higher 5HT2A tended to be less optimistic. These results suggest that the serotonergic and dopaminergic systems are linked to observed cognitive variation, and, thus, individual differences in cognition can be partially explained by variation in brain gene expression.

Bipolar Disorder: Its Etiology and How to Model in Rodents

Characterized by the switch of manic and depressive phases, bipolar disorder was described as early as the fifth century BC. Nevertheless up to date, the underlying neurobiology is still largely unclear, assuming a multifactor genesis with both biological-genetic and psychosocial factors. Significant process has been achieved in recent years in researching the causes of bipolar disorder with modern molecular biological (e.g., genetic and epigenetic studies) and imaging techniques (e.g., positron emission tomography (PET) and functional magnetic resonance imaging (fMRI)). In this chapter we will first summarize our recent knowledge on the etiology of bipolar disorder. We then discuss how several factors observed to contribute to bipolar disorder in human patients can be manipulated to generate rodent models for bipolar disorder. Finally, we will give an overview on behavioral test that can be used to assess bipolar-disorder-like behavior in rodents.

Assessing animal affect: an automated and self-initiated judgement bias task based on natural investigative behaviour

Scientific methods for assessing animal affect, especially affective valence (positivity or negativity), allow us to evaluate animal welfare and the effectiveness of 3Rs Refinements designed to improve wellbeing. Judgement bias tasks measure valence; however, task-training may be lengthy and/or require significant time from researchers. Here we develop an automated and self-initiated judgement bias task for rats which capitalises on their natural investigative behaviour. Rats insert their noses into a food trough to start trials. They then hear a tone and learn either to stay for 2 s to receive a food reward or to withdraw promptly to avoid an air-puff. Which contingency applies is signalled by two different tones. Judgement bias is measured by responses to intermediate ambiguous tones. In two experiments we show that rats learn the task in fewer sessions than other automated variants, generalise responses across ambiguous tones as expected, self-initiate 4-5 trials/min, and can be tested repeatedly. Affect manipulations generate main effect trends in the predicted directions, although not localised to ambiguous tones, so further construct validation is required. We also find that tone-reinforcer pairings and reinforcement or non-reinforcement of ambiguous trials can affect responses to ambiguity. This translatable task should facilitate more widespread uptake of judgement bias testing.

Animal models for bipolar disorder: from bedside to the cage

Bipolar disorder is characterized by recurrent manic and depressive episodes. Patients suffering from this disorder experience dramatic mood swings with a wide variety of typical behavioral facets, affecting overall activity, energy, sexual behavior, sense of self, self-esteem, circadian rhythm, cognition, and increased risk for suicide. Effective treatment options are limited and diagnosis can be complicated. To overcome these obstacles, a better understanding of the neurobiology underlying bipolar disorder is needed. Animal models can be useful tools in understanding brain mechanisms associated with certain behavior. The following review discusses several pathological aspects of humans suffering from bipolar disorder and compares these findings with insights obtained from several animal models mimicking diverse facets of its symptomatology. Various sections of the review concentrate on specific topics that are relevant in human patients, namely circadian rhythms, neurotransmitters, focusing on the dopaminergic system, stressful environment, and the immune system. We then explain how these areas have been manipulated to create animal models for the disorder. Even though several approaches have been conducted, there is still a lack of adequate animal models for bipolar disorder. Specifically, most animal models mimic only mania or depression and only a few include the cyclical nature of the human condition. Future studies could therefore focus on modeling both episodes in the same animal model to also have the possibility to investigate the switch from mania-like behavior to depressive-like behavior and vice versa. The use of viral tools and a focus on circadian rhythms and the immune system might make the creation of such animal models possible.

Measuring Cognitive Judgement Bias in Rats Using the Ambiguous-Cue Interpretation Test

An active-choice, operant, ambiguous-cue interpretation (ACI) paradigm is described that can be used for measuring cognitive judgement bias in rats. In this behavioral test, animals in an operant conditioning chamber are trained to press a lever to receive a food reward when a specific tone is presented, and to press another lever in response to a different tone to avoid punishment by an electric foot-shock. The tones, which serve as discriminative stimuli, acquire a positive or negative valence, and the training continues until the rats demonstrate a stable, correct discrimination between these two stimuli. The animals are tested after they have attained stable discrimination performance. The ambiguous-cue test consists of a discrimination task, as described above, but includes the presentation of additional tones with frequencies that are intermediate between the trained positive and negative tones. The lever-press response pattern to these ambiguous cues is considered an indicator of the rat's expectation of a positive or negative event; in other words, it is a measure of 'optimism' or 'pessimism', respectively. © 2017 by John Wiley & Sons, Inc.

Making Decisions under Ambiguity: Judgment Bias Tasks for Assessing Emotional State in Animals

Judgment bias tasks (JBTs) are considered as a family of promising tools in the assessment of emotional states of animals. JBTs provide a cognitive measure of optimism and/or pessimism by recording behavioral responses to ambiguous stimuli. For instance, a negative emotional state is expected to produce a negative or pessimistic judgment of an ambiguous stimulus, whereas a positive emotional state produces a positive or optimistic judgment of the same ambiguous stimulus. Measuring an animal's emotional state or mood is relevant in both animal welfare research and biomedical research. This is reflected in the increasing use of JBTs in both research areas. We discuss the different implementations of JBTs with animals, with a focus on their potential as an accurate measure of emotional state. JBTs have been successfully applied to a very broad range of species, using many different types of testing equipment and experimental protocols. However, further validation of this test is deemed necessary. For example, the often extensive training period required for successful judgment bias testing remains a possible factor confounding results. Also, the issue of ambiguous stimuli losing their ambiguity with repeated testing requires additional attention. Possible improvements are suggested to further develop the JBTs in both animal welfare and biomedical research.

Modeling mania in preclinical settings: A comprehensive review

The current pathophysiological understanding of mechanisms leading to onset and progression of bipolar manic episodes remains limited. At the same time, available animal models for mania have limited face, construct, and predictive validities. Additionally, these models fail to encompass recent pathophysiological frameworks of bipolar disorder (BD), e.g. neuroprogression. Therefore, there is a need to search for novel preclinical models for mania that could comprehensively address these limitations. Herein we review the history, validity, and caveats of currently available animal models for mania. We also review new genetic models for mania, namely knockout mice for genes involved in neurotransmission, synapse formation, and intracellular signaling pathways. Furthermore, we review recent trends in preclinical models for mania that may aid in the comprehension of mechanisms underlying the neuroprogressive and recurring nature of BD. In conclusion, the validity of animal models for mania remains limited. Nevertheless, novel (e.g. genetic) animal models as well as adaptation of existing paradigms hold promise.

Dopamine induces an optimism bias in rats-Pharmacological proof for the translational validity of the ambiguous-cue interpretation test

Recent findings have revealed that pharmacological enhancement of dopaminergic (DA) function by the administration of a dopaminergic precursor (dihydroxy-l-phenylalanine; l-DOPA) increases an optimism bias in humans. This effect is due to l-DOPA's impairment of the ability to update beliefs in response to undesirable information about the future. To test whether an 'optimistic' bias is also mediated by dopamine in animals, first, two groups of rats received either a dopaminergic precursor, l-DOPA, or a D2 receptor antagonist, haloperidol, and were subsequently tested using the ambiguous-cue interpretation (ACI) paradigm. To test whether similar effects might be observed when manipulating another neurotransmitter implicated in learning about reward and punishment, we administered the serotonin (5-HT) reuptake inhibitor escitalopram to a third group of animals and the selective and irreversible tryptophan hydroxylase inhibitor para-chlorophenylalanine (PCPA) to a fourth group. The results of our study demonstrated that prolonged (2 weeks), but not acute, l-DOPA administration induced optimistic bias in rats. Neither acute nor chronic treatment with the other tested compounds had significant effects on the cognitive judgment bias of rats. The convergence of these results with human studies suggests the translational validity of the ambiguous-cue interpretation paradigm in testing the effects of pharmacological manipulations on cognitive judgment bias (optimism/pessimism) in rats.

Happy hamsters? Enrichment induces positive judgement bias for mildly (but not truly) ambiguous cues to reward and punishment in Mesocricetus auratus

Recent developments in the study of animal cognition and emotion have resulted in the 'judgement bias' model of animal welfare. Judgement biases describe the way in which changes in affective state are characterized by changes in information processing. In humans, anxiety and depression are characterized by increased expectation of negative events and negative interpretation of ambiguous information. Positive wellbeing is associated with enhanced expectation of positive outcomes and more positive interpretation of ambiguous information. Mood-congruent judgement biases for ambiguous information have been demonstrated in a range of animal species, with large variation in the way tests are administered and in the robustness of analyses. We highlight and address some issues using a laboratory species not previously tested: the Syrian hamster (Mesocricetus auratus). Hamsters were tested using a spatial judgement go/no-go task in enriched and unenriched housing. We included a number of controls and additional behavioural tests and applied a robust analytical approach using linear mixed effects models. Hamsters approached the ambiguous cues significantly more often when enriched than unenriched. There was no effect of enrichment on responses to the middle cue. We discuss these findings in light of mechanisms underlying processing cues to reward, punishment and true ambiguity, and the implications for the welfare of laboratory hamsters.

Effects of optimism on motivation in rats

In humans, optimism is a cognitive construct related to motivation; optimists exert effort, whereas pessimists disengage from effort. In this study, using a recently developed ambiguous-cue interpretation (ACI) paradigm we took the unique opportunity to investigate whether "optimism" as a trait is correlated with motivation in rodents. In a series of ACI tests (cognitive bias screening, CBS), we identified rats displaying "pessimistic" and "optimistic" traits. Subsequently, we investigated the trait differences in the motivation of these rats to gain reward and to avoid punishment using a progressive ratio (PR) schedule of reinforcement paradigm. Although "optimistic" and "pessimistic" animals did not differ in their motivation to avoid punishment, the "optimistic" rats were significantly more motivated to gain reward than their "pessimistic" conspecifics. For the first time, we showed an association between cognitive judgment bias and motivation in an animal model. Because both investigated processes are closely related to mental health and wellbeing, our results may be valuable for preclinical modeling of many psychiatric disorders.

Acute administration of lithium, but not valproate, modulates cognitive judgment bias in rats

RATIONALE AND OBJECTIVES

Both valproic acid (VPA) and lithium (LI) are well-established treatments for therapy of intense and sustained mood shifts, which are characteristics of affective disorders, such as bipolar disorder (BP). As mood and cognitive judgment bias have been found to be strongly interrelated, the present study investigated, in an animal model, whether acute treatment with VPA or LI could affect cognitive judgment bias.

METHODS

To accomplish this goal, two groups of rats received single injections of either VPA or LI after initial behavioral training and were subsequently tested with the ambiguous-cue interpretation (ACI) test. Both drugs were administered in three doses using the fully randomized Latin square design.

RESULTS

VPA (100, 200, and 400 mg/kg) had no significant effect on the interpretation of the ambiguous cue. LI at the lowest dose (10 mg/kg) had no effect; at an intermediate dose (50 mg/kg), it significantly biased animals towards positive interpretation of the ambiguous cue, and at the highest dose (100 mg/kg), it impaired the ability of animals to complete the test.

CONCLUSION

To our knowledge, this is the first study demonstrating lithium's effects on increased optimistic judgment bias. Future studies may focus on the ability of putative pharmacotherapies to modify the cognitive judgment bias dimension of patients at risk for bipolar disorder or depression.