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Salient landmarks enhance route learning. We hypothesised that semantically salient nostalgic landmarks would improve route learning compared to non-nostalgic landmarks. In two experiments, participants learned a route through a computer-generated maze using directional arrows and wall-mounted pictures. On the test trial, the arrows were removed, and participants completed the maze using only the pictures. In the nostalgia condition, pictures were of popular music artists and TV characters from 5 to 10 years ago. In the control condition, they were recent pictures of these same artists and characters. In Experiment 1, in the test trial, participants in the nostalgia condition completed the maze faster than controls. Experiment 2 conceptually replicated these findings and extended them by exploring boundary conditions. Participants had to learn two mazes sequentially. In Maze 1, we placed nostalgic/control landmarks only at non-decision points (whereas we placed them at decision points in Experiment 1). In Maze 2, we placed nostalgic/control landmarks at decision points during acquisition but removed them in the test trial (whereas they were present in the test trial in Experiment 1). In both mazes, participants in the nostalgia (compared to control) condition completed the test trial faster.

Early-life adversity impacts on anxiety-related behaviors in adulthood. The effects of such adversity not only affects the animal itself, but can be passed on transgenerationally. Pervasive effects of experimentally-induced early-life stress (ELS) have been documented in adult zebrafish but it is not clear if this can be passed on via the germline. Here, we investigated the effects of ELS across three generations, by analyzing the responses of adult animals exposed to ELS in two different anxiety-related tasks, as well as in social behavior, memory, and cognition. Animals exposed to ELS (at 7 days-post-fertilization) showed a marked attenuation of specific anxiety-related behaviors (F0) when adults, and these alterations were maintained across two subsequent generations (F1and F2). These findings suggest that zebrafish may be a useful model organism to study the transgenerational effects of ELS, and how this pertains to (for example) neuropsychiatric disorders. In addition, our data may naturally provoke questions regarding consideration of the environment of laboratory-housed zebrafish at early developmental stages. In particular, more work may be necessary to determine how different environmental stressors could affect data variability across laboratories.Graphical AbstractSummary of the ELS effects in zebrafish anxiety-like behavior across multiple generations.

ADHD is a highly prevalent neurodevelopmental disorder. The first-line therapeutic for ADHD, methylphenidate, can cause serious side effects including weight loss, insomnia, and hypertension. Therefore, the development of non-stimulant-based therapeutics has been prioritized. However, many of these also cause other effects, most notably somnolence. Here, we have used a uniquely powerful genetic model and unbiased drug screen to identify novel ADHD non-stimulant therapeutics. We first found that adgrl3.1 null (adgrl3.1−/−) zebrafish larvae showed a robust hyperactive phenotype. Although the hyperactivity was rescued by three ADHD non-stimulant therapeutics, all interfered significantly with sleep. Second, we used wild-type zebrafish larvae to characterize a simple behavioral phenotype generated by atomoxetine and screened the 1200 compound Prestwick Chemical Library® for a matching behavioral profile resulting in 67 hits. These hits were re-assayed in the adgrl3.1−/−. Using the previously identified non-stimulants as a positive control, we identified four compounds that matched the effect of atomoxetine: aceclofenac, amlodipine, doxazosin, and moxonidine. We additionally demonstrated cognitive effects of moxonidine in mice using a T-maze spontaneous alternation task. Moxonidine, has high affinity for imidazoline 1 receptors. We, therefore, assayed a pure imidazoline 1 agonist, LNP599, which generated an effect closely matching other non-stimulant ADHD therapeutics suggesting a role for this receptor system in ADHD. In summary, we introduce a genetic model of ADHD in zebrafish and identify five putative therapeutics. The findings offer a novel tool for understanding the neural circuits of ADHD, suggest a novel mechanism for its etiology, and identify novel therapeutics.

Rationale Triangulation of approaches (i.e., using several tests of the same construct) can be extremely useful for increasing the robustness of the findings being widely used when working with behavioral testing, especially when using rodents as a translational model. Although zebrafish are widely used in neuropharmacology research due to their high-throughput screening potential for new therapeutic drugs, behavioral test battery effects following pharmacological manipulations are still unknown. Methods Here, we tested the effects of an anxiety test battery and test time following pharmacological manipulations in zebrafish by using two behavioral tasks: the novel tank diving task (NTT) and the light–dark test (LDT). Fluoxetine and conspecific alarm substance (CAS) were chosen to induce anxiolytic and anxiogenic-like behavior, respectively. Results For non-drug-treated animals, no differences were observed for testing order (NTT → LDT or LDT → NTT) and there was a strong correlation between performances on the two behavioral tasks. However, we found that during drug treatment, NTT/LDT responses are affected by the tested order depending on the test time being fluoxetine effects higher at the second behavioral task (6 min later) and CAS effects lower across time. Conclusions Overall, our data supports the use of baseline behavior assessment using this anxiety test battery. However, when working with drug exposure, data analysis must carefully consider time-drug-response and data variability across behavioral tasks.

Spatial anxiety (i.e., feelings of apprehension and fear about navigating everyday environments) can adversely impact people’s ability to reach desired locations and explore unfamiliar places. Prior research has either assessed spatial anxiety as an individual-difference variable or measured it as an outcome, but there are currently no experimental inductions to investigate its causal effects. To address this lacuna, we developed a novel protocol for inducing spatial anxiety within a virtual environment. Participants first learnt a route using directional arrows. Next, we removed the directional arrows and randomly assigned participants to navigate either the same route (n = 22; control condition) or a variation of this route in which we surreptitiously introduced unfamiliar paths and landmarks (n = 22; spatial-anxiety condition). The manipulation successfully induced transient (i.e., state-level) spatial anxiety and task stress but did not significantly reduce task enjoyment. Our findings lay the foundation for an experimental paradigm that will facilitate future work on the causal effects of spatial anxiety in navigational contexts. The experimental task is freely available via the Open Science Framework (https://osf.io/uq4v7/).

Behavioural needs are highly motivated actions critical to a species survival and reproduction. Prolonged restriction of these behaviours can lead to stereotypic behaviours (SB) in captive animals, and this is particularly common in ungulate species. While risk factors for SB have been suggested for some ungulates, no study has integrated these findings to identify which aspects of ungulates’ wild behavioural biology and captive husbandry are potential drivers for SB across this clade. We collated SB data from 15 236 individuals across 38 ungulate species from 95 sources, and determined species wild/free-ranging behaviour from 559 additional studies. Bayesian-phylogenetic statistical methods showed that ungulate behavioural needs relating to foraging and mating are particularly affected by captive environments, with promiscuous and browsing species showing the greatest prevalence of SB. Concentrate-only diets and lack of ad libitum feed substrates were also associated with high SB prevalence. This study identifies which ungulates are better suited to captive environments and which species require targeted husbandry, enrichment and breeding protocols in order to meet their behavioural needs. Our approach of applying Bayesian-phylogenetic inference to factors influencing SB within a clade can be used to identify other intrinsic and extrinsic risk factors of reduced animal health and welfare.

Spatial anxiety (i.e., feelings of apprehension and fear about navigating everyday environments) can adversely impact people's ability to reach desired locations and explore unfamiliar places. Prior research has either assessed spatial anxiety as an individual-difference variable or measured it as an outcome, but there are currently no experimental inductions to investigate its causal effects. To address this lacuna, we developed a novel protocol for inducing spatial anxiety within a virtual environment. Participants first learnt a route using directional arrows. Next, we removed the directional arrows and randomly assigned participants to navigate either the same route (n = 22; control condition) or a variation of this route in which we surreptitiously introduced unfamiliar paths and landmarks (n = 22; spatial-anxiety condition). The manipulation successfully induced transient (i.e., state-level) spatial anxiety and task stress but did not significantly reduce task enjoyment. Our findings lay the foundation for an experimental paradigm that will facilitate future work on the causal effects of spatial anxiety in navigational contexts. The experimental task is freely available via the Open Science Framework ( https://osf.io/uq4v7/ ).

We explored (1) self-reported changes in alcohol use during the pandemic in the UK and (2) the extent to which self-reported inhibitory control and/or stress were associated with any change in drinking behaviour. We used a UK-based cross-sectional online survey administered to four nationally representative birth cohorts (N = 13,453). A significant minority of 30- (29.08%) and 50-year-olds (26.67%) reported drinking more, and between 32.23 and 45.02% of respondents reported feeling more stressed depending on the cohort. Stress was associated with hazardous drinking among 30-year-olds (OR = 3.77, 95% CI 1.15 to 12.28). Impatience was associated with both increased alcohol use (1.14, 95% CI 1.06, 1.24) and hazardous drinking (1.20, 95% CI 1.05, 1.38) among 19-year-olds. Risk-taking was associated with hazardous drinking for 30-year-olds (OR = 1.18, 95% CI 1.05, 1.32). These data highlight concerns for those at risk of alcohol misuse and alcohol-related harm during COVID-19 lockdowns. Supplementary Information The online version contains supplementary material available at 10.1007/s11469-021-00599-8.

Background: Exposure to stress and trait impulsivity are independent predictors of relapse in recovering alcoholics, but potential mechanisms that link these two risk-factors in terms of their putative additive or interactive contributions to relapse are not known. The aim of this study was to use a model of stress-induced relapse to test the hypothesis that acute psychosocial stress increases craving for alcohol in social drinkers. We also tested the hypothesis that change in craving could be explained by variability in impulsivity and risk-taking.Methods: Participants completed questionnaires to assess drinking behaviour (Alcohol Dependence Questionnaire [ADQ]; and an Alcohol Use Disorders Identification Test [AUDIT]), craving (Desires for Alcohol Questionnaire [DAQ] and impulsivity (Barrett Impulsiveness Scale [BIS]). Participants also completed two computer tasks to assess risk-taking and impulsivity, the Balloon Analogue Risk Test (BART) and a continuous performance task (CPT). Participants then underwent the Trier Social Stress Test (TSST), and completed a final DAQ to assess post-stress craving.Results: Participants showed an increase in craving following exposure to the TSST. In addition, risk-taking was positively correlated with change in craving.Conclusions: Our data suggested that acute psychosocial stress increases subjective craving in social drinkers, but that the effects may be trait-dependent, with stress-induced increases in craving correlated with risk-taking.

Zebrafish are used in anxiety research as the species' naturalistic diving response to a new environment is a reliable and validated marker for anxiety-like behavior. One of the benefits of using zebrafish is the potential for high throughput drug screens in fish at the larval stage. However, at present, tests of anxiety in larvae and adults often measure different endpoints.Here, for the first time, we have adapted the novel tank diving response test for examining diving behavior in zebrafish larvae to assess anxiety-like behaviors at very early-stages (7 days-post-fertilization [dpf]).Current methods to examine anxiety in larvae can show low reliability, and measure different endpoints as in adults, thus calling into question their translational relevance.We found that 7dpf zebrafish spent more time at the bottom of a small novel tank. We validated this as anxiety-like behaviors with diazepam reducing, and caffeine increasing the time spent in the bottom of the novel environment.This new automated and high-throughput screening tool has the potential use for screening of anxiogenic and anxiolytic compounds, and for studies aiming to better understand anxiety-like behaviors.

The use of multiple species to model complex human psychiatric disorders, such as ADHD, can give important insights into conserved evolutionary patterns underlying multidomain behaviors (e.g., locomotion, attention, and impulsivity). Here we discuss the advantages and challenges in modelling ADHD-like phenotypes in zebrafish (Danio rerio), a vertebrate species that has been widely used in neuroscience and behavior research. Moreover, multiple behavioral tasks can be used to model the core symptoms of ADHD and its comorbidities. We present a critical review of current ADHD studies in zebrafish, and how this species might be used to accelerate the discovery of new drug treatments for this disorder.

Neurodevelopmental disorders (NDDs) caused by aberrant brain growth and development are life-long, debilitating illnesses that markedly impair the quality of life. Animal models are a valuable tool for studying NDD pathobiology and therapies. Mounting evidence suggests the zebrafish (Danio rerio) as a useful model organism to study NDDs, possessing both high physiological homology to humans and sensitivity to pharmacological and genetic manipulations. Here, we summarize experimental models of NDDs in zebrafish and highlight the growing translational significance of zebrafish NDD-related phenotypes. We also emphasize the need in further development of zebrafish models of NDDs to improve our understanding of their pathogenesis and therapeutic treatments.

Early life stress (ELS) is defined as a short or chronic period of trauma, environmental or social deprivation, which can affect different neurochemical and behavioral patterns during adulthood. Zebrafish (Danio rerio ) have been widely used as a model system to understand human neurodevelopmental disorders and display translationally relevant behavioral and stress‐regulating systems. In this study, we aimed to investigate the effects of moderate ELS by exposing young animals (6‐weeks postfertilization), for 3 consecutive days, to three stressors, and analyzing the impact of this on adult zebrafish behavior (16‐week postfertilization). The ELS impact in adults was assessed through analysis of performance on tests of unconditioned memory (free movement pattern Y‐maze test), exploratory and anxiety‐related task (novel tank diving test), and social cohesion (shoaling test). Here, we show for the first time that moderate ELS increases the number of alternations in turn‐direction compared to repetitions in the unconditioned Y‐maze task, suggesting increased working memory, but has no effect on shoal cohesion, locomotor profile, or anxiety‐like behavior. Overall, our data suggest that moderate ELS may be linked to adaptive flexibility which contributes to build “resilience” in adult zebrafish by improving working memory performance.

Multiple species display robust behavioral variance among individuals due to different genetic, genomic, epigenetic, neuroplasticity and environmental factors. Behavioral individuality has been extensively studied in various animal models, including rodents and other mammals. Fish, such as zebrafish (Danio rerio), have recently emerged as powerful aquatic model organisms with overt individual differences in behavioral, nociceptive and other CNS traits. Here, we evaluate individual behavioral differences in mammals and fish, emphasizing the importance of cross-species analyses of intraspecies variance in experimental models of normal and pathological CNS functions.

GRIA1 encodes the GluA1 subunit of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptors, which are ligand-gated ion channels that act as excitatory receptors for the neurotransmitter L-glutamate (Glu). AMPA receptors (AMPARs) are homo- or heteromeric protein complexes with four subunits, each encoded by different genes, GRIA1 to GRIA4. Although GluA1-containing AMPARs have a crucial role in brain function, the human phenotype associated with deleterious GRIA1 sequence variants has not been established. Subjects with de novo missense and nonsense GRIA1 variants were identified through international collaboration. Detailed phenotypic and genetic assessments of the subjects were carried out and the pathogenicity of the variants was evaluated in vitro to characterize changes in AMPAR function and expression. In addition, two Xenopus gria1 CRISPR-Cas9 F-0 models were established to characterize the in vivo consequences. Seven unrelated individuals with rare GRIA1 variants were identified. One individual carried a homozygous nonsense variant (p.Arg377Ter), and six had heterozygous missense variations (p.Arg345Gln, p.Ala636Thr, p.Ile627Thr, and p.Gly745Asp), of which the p.Ala636Thr variant was recurrent in three individuals. The cohort revealed subjects to have a recurrent neurodevelopmental disorder mostly affecting cognition and speech. Functional evaluation of major GluA1-containing AMPAR subtypes carrying the GRIA1 variant mutations showed that three of the four missense variants profoundly perturb receptor function. The homozygous stop-gain variant completely destroys the expression of GluA1-containing AMPARs. The Xenopus gria1 models show transient motor deficits, an intermittent seizure phenotype, and a significant impairment to working memory in mutants. These data support a developmental disorder caused by both heterozygous and homozygous variants in GRIA1 affecting AMPAR function.

Zebrafish (Danio rerio) are widely used as a translational model for human neuropsychiatric conditions. Many studies have not considered sex differences in their analyses. Here, we studied sex differences of adult zebrafish in two behavioral domains: Anxiety and Memory. To assess whether sex influences anxiety‐like responses, we used two different behavioral protocols, the novel tank diving task and the light‐dark test. To assess sex differences in learning and memory tasks, we explored two memory domains, short‐term spatial memory (free movement pattern Y‐maze task) and short‐term fear memory (Pavlovian fear conditioning task). Although we did not find any significant difference in learning and memory tasks, female zebrafish showed robust increases in anxiety‐like behavioral endpoints in both anxiety tests. Overall, our data suggest that zebrafish is a sensitive model to work with sex differences when modeling anxiety‐related disorders and this should be an important factor to consider in different experimental designs.

Sex is an important biological variable that is widely recognized in studies of alcohol-related effects. Complementing clinical and preclinical rodent research, the zebrafish (Danio rerio) is the second most used laboratory species, and a powerful model organism in biomedicine. Like clinical and rodent models, zebrafish demonstrate overt sex differences in alcohol-related responses. Collectively, this evidence shows that the zebrafish becomes a sensitive model species to further probe in-depth sex differences commonly reported in alcohol research.

Exposure to anesthetic drugs is common in biomedical sciences being part of routine procedures in different translational species, however its impacts on memory and cognition are still debated, having different impacts depending on drug and age. The zebrafish (Danio rerio) is a translational species widely used in behavioral neuroscience, where tricaine methanesulfonate (MS222) is the most acceptable and used drug when conducting routine procedures. Based on this, we investigated the effects of MS222 (100 mg/l) in young adults and aging zebrafish 1, 2, 3, and 7 days after exposure. Animals’ were submitted to the anesthetic procedure until loss of body posture, slowing of opercular movements and lack of response to tail touch with a plastic pipette were achieved, then further left in the drug for 3 min. After that, animals (6 mpf vs. 24 mpf) were transferred to a recovery tank until fully recovered and transferred back to their housing system until further testing in the free movement pattern (FMP) Y-maze, which assesses zebrafish working memory and cognitive lexibility. Young animals had significant impairment in their working memory and cognitive flexibility 1 and 2 days after the exposure to MS222, being fully recovered by day 3 and with no effects 7 days post drug exposure. Increased repetitions were also observed for animals exposed to MS222 which could indicate increased stress-related response in animals up to 2 days after drug exposure. No drug effect was observed in aging animals besides their natural decreased alternations and working memory. Overall, behavioral experiments after routine procedures using MS222 should be performed with caution and need to be delayed, at least 3 days after exposure where working memory, cognitive flexibility, and repetitive behavior are back to normal.

Healthy aging is associated with a decline in memory and executive function, which have both been linked with aberrant dopaminergic signalling. We examined the relationship between cognitive performance and dopamine function of young and aging zebrafish (Danio rerio). We revealed age-related decreases in working memory and cognitive flexibility in the Free-Movement Pattern (FMP) Y-maze. An increase in drd5 gene expression in aging adults coincided with a decrease in cognitive performance. Treatment with a D1/D5 receptor agonist (SKF-38393, 35 μM) 30 minutes prior to behavioural assessment resulted in improved working memory in aging zebrafish, but no effect in younger adults. However, an ‘overdosing’ effect caused by agonist treatment resulted in downregulation of dat expression in 6-month old, treated zebrafish. The translational relevance of these findings was tested in humans by analysing exploratory behaviour in young-adult, 18-35-year olds, and aged adults, 70+ year olds, in a virtual FMP Y-maze. Our findings revealed similar age-related decline in working memory. Thus, strongly supporting zebrafish as a translational model of aging and cognitive decline.

Introduction: Depression is a highly debilitating psychiatric disorder that affects the global population and causes severe disabilities and suicide. Depression pathogenesis remains poorly understood, and the disorder is often treatment-resistant and recurrent, necessitating the development of novel therapies, models and concepts in this field.Areas covered: Animal models are indispensable for translational biological psychiatry, and markedly advance the study of depression. Novel approaches continuously emerge that may help untangle the disorder heterogeneity and unclear categories of disease classification systems. Some of these approaches include widening the spectrum of model species used for translational research, using a broader range of test paradigms, exploring new pathogenic pathways and biomarkers, and focusing more closely on processes beyond neural cells (e.g. glial, inflammatory and metabolic deficits).Expert opinion: Dividing the core symptoms into easily translatable, evolutionarily conserved phenotypes is an effective way to reevaluate current depression modeling. Conceptually novel approaches based on the endophenotype paradigm, cross-species trait genetics and ‘domain interplay concept’, as well as using a wider spectrum of model organisms and target systems will enhance experimental modeling of depression and antidepressant drug discovery.

Acute stressors are recurrent in multiple species' lives and can facilitate or impair cognition. The use of zebrafish (Danio rerio) as a translational species to understand the mechanisms by which stress induces different behavioral phenotypes has been widely studied. Two acute stressors are recognized when using this species: (1) conspecific alarm substance (CAS); and (2) net chasing. Here, we tested if CAS or net chasing would affect working memory and cognitive flexibility by testing performance in the FMP Y-maze after exposure to stress. We observed that CAS altered zebrafish behavioral phenotypes by increasing repetitive behavior; meanwhile, animals showed different patterns of repetitive behavior when exposed to net chasing, depending on the chasing direction. Because D1 receptors were previously studied as a potential mechanism underlying stress responses in different species, here, we pretreated fish with a D1/D5 agonist (SKF-38393) to assess whether this system plays a role in repetitive behavior in the FMP Y-maze. The pretreatment with D1/D5 agonist significantly decreased repetitive behavior in CAS exposed animals, and cortisol levels for both stressed groups, suggesting that the dopaminergic system plays an important role in zebrafish stress-related responses.

SummaryBackgroundThe impact COVID-19 on the UK population’s alcohol intake is unknown. We assessed change in alcohol-use and hazardous drinking during the first lockdown, and tested the hypothesis that variation would be predicted by stress and inhibitory-control.MethodsWe interrogated cross-sectional data from the first sweep of the COVID-19 longitudinal survey, comprising 4 national cohorts (13 453 respondents, 19-62 years). Respondents self-reported their alcohol use, stress, and inhibitory control. We regressed change in drinking and alcohol misuse on stress and inhibitory control, adjusting for covariates to account for demographics.Findings29·08% 30-year-olds increased alcohol use post-COVID-19. Stress was a major contributing factor to increased alcohol use in 30-year olds (adjusted OR 3·92, 95% CI 1·17 - 13·15), as was inhibitory control in 19-year-olds (adjusted OR 1·14, 95% CI 1·05 - 1·23), 30-year-olds (adjusted OR 1·18, 95% CI 1.05 - 1.33) and 50-year-olds (adjusted OR 1·06, 95% CI 1·01 - 1·12). We identified several interactions between stress and inhibitory control in all age groups, suggesting a complex age-specific relationship between the risk factors and alcohol use and misuse during the pandemic.InterpretationIn the UK, alcohol use increased in up to 30% of the population during COVID-19, resulting from a combination of factors including poor inhibitory control and stress. It is critical in future lockdowns that clinicians and public health officials are aware of the challenges faced by different age groups, and prioritise and personalise interventions and prevention measures appropriately.FundingESRC, Foundation for Liver Research.Putting research into contextEvidence before the studyWe searched PubMed, Web of Science, EBSCO Discovery, bioRxiv, medRxiv, and PsyArXiv for articles published between Jan 1, 2020 and Sep 1, 2020, with the following keywords: “covid-19”, “coronavirus”, and “alcohol”. We prioritised the selection of references based on relevance, importance, opportunity for further reading, and whether the work had been peer-reviewed. There have been several published articles that address the issue of alcohol use and misuse during COVID– 19, including a number of editorials and some limited empirical work. There were no nationally representative studies about alcohol use in the UK. In addition, all of the studies identified simply reported figures of those using alcohol during the pandemic, and to the best of our knowledge, none covered risk-factors for alcohol misuse.Added value of this studyUsing data from the COVID-19 national longitudinal survey (first sweep), comprising data from 18 000 people across five national cohorts (aged 19-74), we tested the hypothesis that people who reported higher levels of stress, and who self-reported low impulse-control, would show higher rates of alcohol use/misuse during the pandemic lockdown. First, we show the proportion of adults across the UK that are drinking more during the pandemic, and how this differs by age and gender. Second, we show that while higher levels of stress were associated with higher levels of alcohol intake in some (e.g., 30-year-olds), we found that the relationship was complex and multifaceted. Stress-induced alcohol use and misuse was dependent on age and personality characteristics, with low impulse-control predictive of higher levels of alcohol consumption in 19-, 30- and 50-year-olds, and several stress x personality interactions.Implications of all the available evidenceStress, as well as poor inhibitory control, were risk factors for the susceptibility to increased alcohol intake and hazardous drinking during the early stages of the COVID-19 pandemic and lockdown. The government, healthcare professionals, and the global media should consider the impact of change of lifestyle and stress that might impact on alcohol consumption among at-risk individuals during any future lockdowns. Similarly, additional support for those that may go on to develop an alcohol use disorder or relapse needs to be put in place.

Numerous neurodegenerative and psychiatric disorders are associated with deficits in executive functions such as working memory and cognitive flexibility. Progress in developing effective treatments for disorders may benefit from targeting these cognitive impairments, the success of which is predicated on the development of animal models with validated behavioural assays. Zebrafish offer a promising model for studying complex brain disorders, but tasks assessing executive function are lacking. The Free-movement pattern (FMP) Y-maze combines aspects of the common Y-maze assay, which exploits the inherent motivation of an organism to explore an unknown environment, with analysis based on a series of sequential two-choice discriminations. We validate the task as a measure of working memory and executive function by comparing task performance parameters in adult zebrafish treated with a range of glutamatergic, cholinergic and dopaminergic drugs known to impair working memory and cognitive flexibility. We demonstrate the cross-species validity of the task by assessing performance parameters in adapted versions of the task for mice and Drosophila, and finally a virtual version in humans, and identify remarkable commonalities between vertebrate species’ navigation of the maze. Together, our results demonstrate that the FMP Y-maze is a sensitive assay for assessing working memory and cognitive flexibility across species from invertebrates to humans, providing a simple and widely applicable behavioural assay with exceptional translational relevance. Electronic supplementary material The online version of this article (10.3758/s13428-020-01452-x) contains supplementary material, which is available to authorized users.

BACKGROUND: Although there is clear evidence of genetic contributions to susceptibility to nicotine addiction, it has proved difficult to identify causal alleles and pathways from studies in humans. Mutagenesis in model species generates strong phenotypes not present in wildtype populations and can be used to identify biological mechanisms underlying quantifiable behaviours. We tested the hypothesis that a forward genetic screen for nicotine preference in zebrafish can predict loci and biological mechanisms influencing human smoking behaviour. METHODS: A population-based forward genetic screen of ethylnitrosurea- mutagenized zebrafish was used to identify lines of fish showing altered nicotine preference. Immunohistochemical, behavioral and quantitative PCR analyses were used to characterize mutant larvae. Focussed SNP analysis of the homologous human locus in cohorts from the UK and a Finnish Twin study assessed the predictive validity of the zebrafish data for human smoking behavior. RESULTS: We show nicotine preference is heritable in fish as in humans and identify loss-of-function mutations in the zebrafish Slit3 gene as associated with increased nicotine preference. Slit3 mutant larval fish showed altered sensitivity of habituation to acoustic startle to dopaminergic antagonists and increased Drd2 and Drd3 mRNA expression. Dopaminergic neuronal pathfinding was unaffected. Analysis of the SLIT3 locus in two independent human cohorts identified 2 genetic markers that predict level of cigarette consumption and likelihood of cessation. CONCLUSION: These findings suggest a role for SLIT3 signaling in development of dopaminergic pathways affecting behaviours associated with nicotine dependence and confirm the translational relevance of the zebrafish model in exploring complex human behaviors.

Simple mazes have provided numerous tasks for assessing working memory. The discrete nature of choices in the T-maze has provided a robust protocol with sensitivity to cognitive deficits, whilst the continuous Y-maze reduces manual handling and pre-trial training. We have combined these attributes to develop a new behavioural task for assessing working memory, the Free-movement pattern (FMP) Y-maze. Using sequentially recorded left and right turns we demonstrate that zebrafish and mice use a single dominant strategy predominantly consisting of alternations between left and right choices trial-to-trial. We further tested this protocol with Drosophila and discovered an alternative invertebrate search strategy. Finally, a virtual human FMP Y-maze confirmed a common strategy among all tested vertebrate species, validating the translational power of the task for human research. The FMP Y-maze combines robust investigation of working memory and high translational power, generating a simple task with far-reaching impact.

Although aggression is a common symptom of psychiatric disorders the drugs available to treat it are non-specific and can have unwanted side effects. In this study we have used a behavioural platform in a phenotypic screen to identify drugs that can reduce zebrafish aggression without affecting locomotion. In a three tier screen of ninety-four drugs we discovered that caffeine and sildenafil can selectively reduce aggression. Caffeine also decreased attention and increased impulsivity in the 5-choice serial reaction time task whereas sildenafil showed the opposite effect. Imaging studies revealed that both caffeine and sildenafil are active in the zebrafish brain, with prominent activation of the thalamus and cerebellum evident. They also interact with 5-HT neurotransmitter signalling. In summary, we have demonstrated that juvenile zebrafish are a suitable model to screen for novel drugs to reduce aggression, with the potential to uncover the neural circuits and signalling pathways that mediate such behavioural effects.

Social behavior represents a beneficial interaction between conspecifics that is critical for maintaining health and wellbeing. Dysfunctional or poor social interaction are associated with increased risk of physical (e.g., vascular) and psychiatric disorders (e.g., anxiety, depression, and substance abuse). Although the impact of negative and positive social interactions is well-studied, their underlying mechanisms remain poorly understood. Zebrafish have well-characterized social behavior phenotypes, high genetic homology with humans, relative experimental simplicity and the potential for high-throughput screens. Here, we discuss the use of zebrafish as a candidate model organism for studying the fundamental mechanisms underlying social interactions, as well as potential impacts of social isolation on human health and wellbeing. Overall, the growing utility of zebrafish models may improve our understanding of how the presence and absence of social interactions can differentially modulate various molecular and physiological biomarkers, as well as a wide range of other behaviors.

Rationale Chronic alcohol misuse can escalate into alcohol use disorder (AUD). The causal mechanisms through which recreational social drinking develops into compulsive uncontrolled alcohol misuse are multifaceted. For example, stress is an important risk factor that influences alcohol craving in both healthy and addicted individuals. In addition, those that are high in impulsivity/risk taking drink more and are at greater risk of developing addiction. At present, however, it is not possible accurately to predict those at risk of escalation in alcohol use, or of developing AUD. Objectives The aim of this study was to investigate how underlying physiological and personality traits affect stress-induced craving for, and consumption of, alcohol, in a sample of social drinkers. The primary hypothesis was that impulsivity/risk-taking would modulate stress-induced alcohol craving and consumption. Methods Thirty-nine participants (22 male and 17 female; mean age = 23.92 years [SD = 4.90]) were randomly allocated to ‘stress’ and ‘no-stress’ groups; in the stress group, participants took part in the Trier Social Stress Test (TSST). Participants completed several questionnaires and computer tasks in order to assess prior alcohol use, impulsivity/risk-taking, stress-reactivity, craving and physiological biomarkers of stress. Finally, participants completed a voluntary drinking task, in which increasing numbers of presses on a computer keyboard were reinforced with 5-ml shots of 37% ABV vodka (plus mixer). Results Participants exposed to the TSST showed an increase in craving following the stressor. Several factors predicted voluntary drinking, including risky decision making, slow HR recovery from stress, poor vagal tone during recovery from stress and greater stress reactivity. Surprisingly, we found no correlation between craving and consumption. Conclusions Our data suggest that variation in physiological stress parameters and poor decision-making abilities increase risk of stress-induced alcohol consumption. This may provide a useful translational framework through which we can further study early predictive markers for the shift between controlled recreational drinking to uncontrolled alcohol misuse, including AUD. Electronic supplementary material The online version of this article (10.1007/s00213-018-5027-0) contains supplementary material, which is available to authorized users.

Behaviour in ecotoxicology is expanding with techniques and endpoints used in pharmacology being translated to other vertebrate and invertebrate species. Despite this, data on the baseline behaviours of model organisms, and inter-species variability in behaviour are currently under-studied. This study assessed a range of behaviours associated with anxiety including swimming speed, phototaxis and thigmotaxis in a marine and freshwater amphipod (Echinogammarus marinus and Gammarus pulex). Differences in sensitivity to these assays were observed between species with E. marinus showing a greater sensitivity to the phototaxis assay than G. pulex, while in thigmotaxis assays G. pulex appeared better suited than E. marinus for measuring differences in the use of central zones. Significant inter-species differences were also observed in swimming patterns when breaking the data into ten second time bins but not when data was broken into two-minute time bins. The results of this study provide evidence of phototactic and thigmotactic behaviours in two model crustacean species with potential for use in behavioural ecotoxicology. Inter-species variability in sensitivity to behavioural assays highlights the importance of systematic assessment of baseline responses for all model species used in behavioural studies. Careful analysis of data is also required when performing behavioural studies so as not to lose sensitivity in your data.

Taurine (TAU) is a β-amino sulfonic acid with pleiotropic roles in the brain, including the neuromodulatory activity via GABAergic and glycinergic agonism. This molecule is found at high concentrations in energy drinks and is often mixed with alcohol in beverages. Although TAU has a neuroprotective role in the brain, the putative risks of mixing TAU and EtOH are not fully understood. Here, we investigated whether TAU modulates locomotor and anxiety-like behavior in adult zebrafish by using the novel tank and light-dark tests following acute EtOH exposure at anxiogenic and anxiolytic concentrations. Zebrafish were individually exposed to water (control), TAU (42, 150, and 400 mg/L), and EtOH (0.25% (v/v) and 1% (v/v)) both independently and cotreated for 1 h. EtOH 0.25% and TAU produced U-shape anxiolytic-like behavior in the light-dark test, TAU 42 and 400 positively modulated EtOH effects, and TAU 150 exerted a protective effect. All TAU concentrations counteracted EtOH 1%-induced locomotion impairment, as well as the anxiogenic-like behavior. Finally, all TAU concentrations when given independently or cotreated with EtOH 0.25% and 1% decreased the risk assessment of the lit compartment. Principal component analyses revealed that exploration and anxiety-like responses were the main behaviors that contribute to the effects of TAU and EtOH. Overall, we demonstrate that TAU differently modulates EtOH-induced anxiolytic- and anxiogenic-like behaviors depending on the concentration, suggesting a complex mechanism underlying TAU and EtOH interactions.

Crib-biting is a repetitive and compulsive behavior that is characterized by "grasping a fixed object with incisor teeth and aspirating air with an audible grunt." Little is known about etiology and pathophysiology of crib-biting behavior in horses. Previously, we have shown that oxidative stress is linked to crib-biting, with crib-biters showing lower antioxidant capacity than non–crib-biting horses. The aim of the present study was to extend our understanding of oxidative stress in crib-biting to determine the serum contents of some mineral trace elements (manganese [Mn], magnesium [Mg], selenium [Se], copper [Cu], and zinc [Zn]), and electrolytes (sodium [Na], potassium [K], calcium [Ca], and phosphorus [P]). Also, the activity of enzymes (alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and gamma glutamyl transferase), some hormones (cortisol, ghrelin, β-endorphin, and serotonin) and blood biochemistry values of various parameters was measured to evaluate their possible association with crib-biting behavior in horses. Blood samples were taken from all horses under the following conditions: basal conditions of crib-biting horses, during or immediately after crib-biting periods, and from non–crib-biting, healthy horses (control group). Serum Se concentration was significantly lower ( P ≤ 0.001) in crib-biting horses than in controls, with the lowest levels seen during crib-biting behavior. Other measured parameters did not differ between acute crib-biting horses and healthy controls. These observations suggest that alterations in serum Se, an important component of the antioxidant system, may play a role in the pathophysiology of crib-biting behavior in horses, adding further evidence to the theory that crib-biting may be related to increased oxidative stress and alterations in essential trace elements.

Background Zebrafish have been widely used to study anxiety-related phenotypes using the novel tank test (NTT). Although the NTT is well-characterized and commonly used by researchers, there is still a lack of information regarding how different experimental variables such as water quality can influence NTT performance. Zebrafish use different chemical cues and olfactory stimuli to communicate in water, so we predicted that water change frequency would affect cortisol, locomotion and anxiety-related parameters in the NTT. New methods After extensive literature research, we found that only about 18% of papers using NTT report partial or complete water changes between subjects. Here, we tested multiple zebrafish in the NTT using the same water up to 9 consecutive times (with no water change) and analyzed cortisol levels, as a stressrelated marker. Results We found that when using the same water for more than 4 trials, data variability is increased and a higher number of extreme values is observed for the time spent in the top zone and immobility. Moreover, after 4 trials with no water change, increased cortisol levels are observed, indicating that animals show increased stressrelated responses with the lack of water changes. Conclusions This study shows that lack of water change can significantly influence zebrafish stress-responses in the NTT. Altogether, behavioral experiments should avoid using the same water when testing multiple fish in the task, especially when looking at anxiety in the NTT.

BackgroundLarge animal models of human neurological disorders are advantageous compared to rodent models due to their neuroanatomical complexity, longevity and their ability to be maintained in naturalised environments. Some large animal models spontaneously develop behaviours that closely resemble the symptoms of neural and psychiatric disorders. The horse is an example of this; the domestic form of this species consistently develops spontaneous stereotypic behaviours akin to the compulsive and impulsive behaviours observed in human neurological disorders such as Tourette’s syndrome. The ability to non-invasively probe normal and abnormal equine brain function through cognitive testing may provide an extremely useful methodological tool to assess brain changes associated with certain human neurological and psychiatric conditions.New methodAn automated operant system with the ability to present visual and auditory stimuli as well as dispense salient food reward was developed. To validate the system, ten horses were trained and tested using a standard cognitive task (three choice serial reaction time task (3-CSRTT)).ResultsAll animals achieved total learning criterion and performed six probe sessions. Learning criterion was met within 16.30 ± 0.79 sessions over a three day period. During six probe sessions, level of performance was maintained at 80.67 ± 0.57% (mean ± SEM) accuracy.Comparison with existing method(s)This is the first mobile fully automated system developed to examine cognitive function in the horse.ConclusionsA fully-automated operant system for mobile cognitive function of a large animal model has been designed and validated. Horses pose an interesting complementary model to rodents for the examination of human neurological dysfunction.

Early-life stress can lead to two different behavioral responses: (1) increased susceptibility to psychiatric disorders or (2) resilience. Here, we created a chronic unpredictable early-life stress (CUELS) protocol to assess the effects of early experiences in adult zebrafish. Animals were exposed to mild stressors twice a day and the duration was varied between groups (0, 1, 3, 7 and 14 days of stress). The stressor consisted of light/dark cycle changes; social isolation; overcrowding; water changes; water cooling; mechanical stirring; water heating; and immersion in shallow water. Behavior was assessed at young stages (21 days post-fertilization – open field analysis) and adulthood (4-months-old - novel tank diving test, light/dark task, shoaling, free movement pattern Y-maze and Pavlovian fear conditioning). Cortisol levels were assessed to evaluate the impact of CUELS in the HPI axis. Zebrafish exposed to 7 days of CUELS showed a decreased anxiety-like phenotype in two behavioral tasks, presenting increased time spent in top and decreased time spent in the dark area. Animals exposed to 14 days of CUELS showed an opposite anxious phenotype compared to 3 and 7 days of CUELS. No significant changes were observed in memory and cognition, social behavior and cortisol levels. In general, 7 days of CUELS protocol decreased anxiety in young and adult zebrafish, and could be used to understand the mechanisms underlying early-life experiences-derived alterations in neural circuits of anxiety.

Crib biting is a common equine stereotypic behavior that has links to health problems and poor welfare. There is evidence that crib biters may be more sensitive to environmental stressors, and the aim of the present study was to test the hypothesis that crib-biting behavior in horses has a relationship with oxidative stress, antioxidant defense, or inflammatory proteins, as is observed in humans with various affective disorders such as depression and anxiety. Ten crib-biting horses and 10 age- and sex-matched healthy horses were used. Vital signs (heart rates, respiratory rates, and temperature) and blood samples were taken in 3 conditions; basal condition for crib biters (no stereotypic behavior observed for at least 30 minutes); crib biters during or directly after crib-biting periods ("acute crib biting" = crib biting for at least 15 minutes with no interruption longer than 2 minutes); non–crib-biting horses (control). Comparisons were made between crib biters and controls, and between crib-biters' basal and crib-biting values. No changes were observed in the vital signs. Total antioxidant capacity activity was significantly decreased in crib biters during the basal measurements relative to controls, and this was significantly decreased again during an episode of crib biting. Similar differences to those observed in total antioxidant capacity were also observed for the antioxidant enzymes superoxide dismutase, glutathione peroxidase, and catalase. Collectively, our data suggest that the antioxidant levels and antioxidant defenses against lipid peroxidation are reduced in crib biters, suggesting that oxidative stress plays a role in the pathophysiology of crib biting. In addition, our data suggest that further study on the role of oxidative stress in crib biting might be of benefit, particularly in the search for veterinary treatments or interventions for crib-biting horses.

Stereotypic behaviors are commonly observed in domestic equids as they are in a range of captive nondomesticated species. Estimates suggest that 19.5%-32.5% of horses perform a stereotypy. The presence of these behaviors is thought to indicate suboptimal welfare status and can result in secondary physical pathologies, such as colic, ligament strain, and incisor wear. Relatively little is understood about the etiologies of oral and locomotor stereotypies. Seemingly disparate causal factors have been proposed, including gastric pathology, neural adaptation, and genetic predisposition. In this review, we propose a model of causality that presents separate pathways to the development and continuation of oral behaviors such as crib-biting, compared with locomotor alternatives (i.e., weaving). The word stereotypy has alarmingly negative connotation among horse keepers. Stereotypic behaviors are often viewed as vices, and therefore, a number of horse owners and establishments attempt to physically prevent the behavior with harsh mechanical devices. Such interventions can result in chronic stress and be further detrimental to equine welfare. Stereotypy has been proposed to be a stress coping mechanism. However, firm evidence of coping function has proven elusive. This review will explore management options directed at both prophylaxis and remediation.

The purpose of the study reported in this Research Communication was to evaluate alterations in concentration of total antioxidant capacity (TAC) of plasma, plasma total thiols as markers of oxidative protein damage and malondialdehyde (as a final product of lipid peroxidation) in samples obtained at different stages of the lactation cycle and dry period of dairy cows. We found that TAC was significantly lower in the primiparous cows compared to multiparous cows. This study clearly demonstrates a need for monitoring primiparous cows during the production cycle, especially when they are faced with severe metabolic conditions. Furthermore, TAC may be a sensitive, reliable and useful indicator for measurement of cumulative effects of antioxidants as an addition to metabolic profile tests, which are currently used to analyse dairy cattle health.