Frontiers in Behavioral Neuroscience

Alterations in rodent self-grooming have been used to model various facets of neuropsychiatric illness. In the context of affective behavior, increases in grooming have been proposed as a sign of stress. This is because grooming has been observed to increase in close temporal proximity to stressful events. However, in other situations, stress appears to suppress grooming, complicating the utility of measuring grooming in the study of stress and mental health. Here, we show that this discrepancy can be resolved by considering time and experimental context. We found that in initial response to stress, grooming declined in proportion to stressor intensity. Moreover, stress-related cues and anxiogenic stimuli similarly suppressed grooming. Conversely, optogenetic inhibition of the amygdala in a stress-associated context decreased threat-elicited freezing, consistent with a reduction in stress, and increased grooming. These results indicate that the immediate response to stress is a suppression of grooming. However, when stressed mice were returned to their homecage environment, grooming increased. Similarly, mice increased grooming when they returned to the safe zone in an anxiety assay. Accordingly, rather than being a defensive response to signs of danger, increased grooming seems to reflect a post-stress response that occurs once animals detect the absence of danger. These findings suggest that post-stress grooming could provide a window into the neurobiology of post-stress recuperative processes.

RationaleAdolescence is a period of heightened vulnerability to nicotine reinforcement. While zebrafish are a valuable model for investigating drug reward, standard conditioned place preference (CPP) assays typically test subjects in isolation. In this highly social species, solitary testing may act as an environmental stressor that confounds behavioral readouts. ObjectivesThis study examined how social context during testing (isolated vs. grouped) affects experimental attrition, behavioral stability, and nicotine CPP expression in late juvenile zebrafish. MethodsZebrafish housed in groups of four were tested either individually (isolated) or in their housing groups (grouped) during daily 20-minute sessions. Following baseline preference assessments, subjects underwent six days of conditioning pairing their initially non-preferred compartment with fish water or nicotine (0.5, 1.6, or 5.0 {micro}mol/L). Place preference, locomotion, and thigmotaxis were assessed on a drug-free test day. ResultsIsolated testing reduced distance traveled, decreased swimming speed, and increased time spent near tank walls, indicating heightened anxiety-like behavior. Experimental attrition was significantly higher in isolated (38.9%) than grouped (2.5%) subjects. Grouped subjects developed significant place preference at 1.6 and 5.0 {micro} mol/L nicotine, whereas preference was not detectable in isolated subjects. ConclusionsSolitary testing acts as a stressor that increases experimental attrition and masks place preference. Conversely, testing in the presence of conspecifics stabilizes behavior and facilitates the detection of nicotine reward in late juvenile zebrafish.

The platform-mediated active avoidance (PMA) task has been used as a rodent model of decision-based active avoidance in which rat learn to avoid a tone-signaled shock. Prior studies utilizing the PMA task have primarily investigated avoidance, freezing, and food-seeking behaviors, but few studies have thoroughly assessed darting behavior, a more recently identified measure of fear that has been largely explored in conditional fear paradigms. Here, we investigated the properties of darting that occur during the PMA task, in which rats either acquired the PMA task alone or with a social partner. We found that rats undergoing solitary PMA produced significantly more darting bouts, whereas rats undergoing social partner PMA produced darts that were faster and shorter in duration. We also found that darting in solitary PMA was predominantly concentrated at the platform, whereas darting in social partner PMA occurred more often outside of the platform and lever zones. Analysis of darting trajectories, which included movements surrounding each darting bout, revealed that darting was embedded in a broader movement strategy between the platform and lever zones, especially during solitary PMA, and this pattern increased across training days. These findings suggest that darting during the PMA task serves as a learned strategy to navigate between reward and safety and is modulated by social context, which is distinct from escape-like darting observed in auditory fear conditioning.

It is widely believed that starvation favours the processing of food-related cues, a notion here called the adaptive specificity hypothesis. Indeed, in Drosophila melanogaster starvation is required for appetitive odour-sugar but not for aversive odour-shock memory. Results from Gruber et al. (2013) and Meschi et al. (2024), however, suggest that starvation improves aversive short-term memory, too, challenging this hypothesis. We survey how starvation affects Drosophila associative olfactory short-term memory across 26 learning tasks. These tasks differ in the reinforcers and the amount of training, the life stage of the animals, in the predictive structure and associative timing of the task, in whether memory is expressed as an increase or decrease in odour preference, and in whether the learned behaviour is motivated by obtaining reward or avoiding/ escaping punishment. In adult flies, an improvement was observed for appetitive odour-sugar memories, whereas all tasks yielding aversive memory were unaffected. Strikingly, appetitive tasks that are not sugar-related, namely odour-shock extinction learning and punishment-relief associations, were either unaffected or even impaired, supporting the adaptive specificity hypothesis. In contrast, in 5-day-old larvae sugar-related appetitive associations were compromised, and the same was observed, to varying degrees, in larvae starved one day earlier and for aversive quinine associations, challenging the adaptive specificity hypothesis. Furthermore, we observed starvation-induced changes in locomotion and preference for a subset of the cues used in our study. Our results defy a simplistic interpretation in terms of the adaptive specificity hypothesis and call for case-by-case analyses of how starvation affects learning and behaviour.

Post-traumatic stress disorder (PTSD) and alcohol use disorder (AUD) are chronic psychiatric disorders that have overlapping symptomology and risk factors, including altered motivation and impulsive behavior. Inescapable exposure to a predator odor stressor (2,3,5-Trimethyl-3-Thiazoline (TMT)) produces PTSD-like symptomology in rats. Individual differences in stress-coping behaviors such as freezing and defensive digging during TMT exposure can predict long-term differences in alcohol-related behaviors and altered neurobiology. Here, we sought to evaluate the relationship between stress coping behavior during TMT exposure and different aspects of decision making. In Experiment 1, male and female rats were trained on an adjusting-amounts delay discounting task, and delay discounting curves were established before and >2 weeks after TMT exposure. In Experiment 2, female rats were trained to self-administer alcohol and sucrose in a concurrent choice procedure. Lever responses and preference for alcohol over sucrose were evaluated before and >2 weeks after TMT exposure, and then motivation for competing reinforcers was evaluated using progressive ratios. Active coping (digging) during TMT exposure was correlated with increased post-TMT impulsive choice (Experiment 1), reduced sucrose lever responses both before and after TMT exposure (Experiment 2), and reduced sucrose lever breakpoint (Experiment 2). Additionally, TMT-exposed rats had increased motivation for both alcohol and sucrose self-administration when available concurrently (Experiment 2). Overall, these findings suggest that behavior prior to and during a stressful experience can predict susceptibility to negative effects on decision making, which may help future studies identify the neurobiology underlying risk for aberrant reward-related behaviors after a traumatic event.

Stress can cause or exacerbate psychiatric illness, and effects on the transcription factor CREB within the nucleus accumbens (NAc) are critically involved. In rodents, stress-induced activation of NAc CREB produces elevations in dynorphin (DYN), an endogenous opioid expressed in dopamine D1-receptor (D1R)-expressing medium spiny neurons (MSNs). In turn, elevated DYN signaling produces features of mood and anxiety disorders via actions at kappa-opioid receptors (KORs). Although individual differences in stress sensitivity have been described--with some appearing susceptible and others resilient--the contribution of NAc DYN to these phenotypes is unclear. Here we examined relationships between social behavior and DYN in D1R-expressing MSNs in mice exposed to chronic social defeat stress (CSDS). We used quantitative (q)RNAscope to assess co-expression of genes encoding CREB (Creb1), D1Rs (Drd1), and DYN (Pdyn) within the NAc. To leverage individual variability, we performed regression analyses across all mice, revealing negative correlations between social interaction behavior and expression of Drd1 and Pdyn, linking higher social avoidance with higher expression of these genes. There was no correlation with Creb1, suggesting stress-induced elevations in Pdyn depend on CREB activation (phosphorylation). These findings suggest that stress-induced elevations in D1R-associated DYN signaling within the NAc is a biomarker of susceptibility.

Rationale: Early life stress (ELS) is acknowledged to underlie cognitive and emotional abnormalities linked to stress-related mood disorders. ELS can lead to persistent biases in how uncertain feedback is processed to affect the flexibility of decision-making. Objectives: (1) To investigate the effects of ELS on the flexibility of rats trained on a serial probabilistic reversal learning (PRL) task involving spurious positive and negative feedback. (2) To elucidate the involvement of the stress hormone corticosterone and the noradrenergic and serotonergic systems in modulating how ELS affects PRL. Methods: Male and female rats were intermittently separated from maternal care on postnatal days five to nineteen, inclusively. As adults, the same rats were trained on a deterministic reversal learning task involving certain rewarded or non-rewarded outcomes followed by a PRL task where correct and incorrect responses were rewarded on 80% and 20% of trials, respectively. Dose-dependent effects of the beta-blocker, propranolol, selective serotonin reuptake inhibitor, citalopram and corticosterone were subsequently determined. Results: ELS resulted in an increased responsivity to feedback, specifically in males making more win-stay responses following a reward, that was associated with an increased punishment learning rate. In both control and MS rats, propranolol increased feedback sensitivity, but delayed updating following a rule switch. In contrast, neither citalopram nor corticosterone significantly affected reversal learning. Conclusions: ELS is sufficient to cause persistent changes in how feedback is processed by male rats on a reversal learning task. Activation of beta-adrenergic receptors may be necessary for updating learned associations during decision-making involving uncertain feedback.

Relapse-prevention strategies aimed at reducing relapse following abstinence, primarily focus on reducing cravings that lead to drug-seeking triggered by stress, drug-related cues, or re-exposure to the drug. Because addictive drugs form persistent associative contextual memories, we investigated how reactivation of cocaine-related hippocampal memories influences subsequent drug-seeking. Here, we tagged dorsal dentate gyrus (dDG) memory ensembles involved in encoding either a first or fourth cocaine exposure (15mg/kg, i.p) in male and female c57BL/6 mice using a TetTag approach. Mice underwent cocaine conditioned place preference (CPP), extinction, and reinstatement. We assessed whether optical reactivation of tagged cocaine-related ensembles could substitute for a cocaine priming injection to reinstate CPP, whether reactivation altered cocaine-induced reinstatement, and if these effects differed depending on stage of drug exposure. We also compared these effects to reactivation of saline-associated ensembles. Cocaine produced robust locomotor activation during conditioning, and sensitization developed across repeated drug exposures. Reactivation of a cocaine-related engram alone did not reinstate CPP. However, reactivation of the first cocaine exposure engram attenuated cocaine-induced reinstatement. In contrast, reactivation of the fourth exposure engram did not confer this protective effect. Interestingly, reactivation of saline-associated ensembles also reduced cocaine-induced reinstatement specifically in females, suggesting dDG ensemble reactivation may modulate relapse-related behavior through interference or neuromodulatory disruption of cocaine-associated representations, consistent with our prior work. These findings raise the possibility that early contextual experiences form competing or destabilizing representations that interfere with later cocaine-seeking when reactivated. Females also displayed greater sensitivity to locomotor-inducing effects of cocaine memory reactivation, although this was dissociated from CPP. Together, these findings show that cocaine memories are distinct across drug experience and selective reactivation of dDG engrams can differentially influence drug-seeking.

Studies of visual discrimination in rodents can confound the effects of cue salience with reward value, making it difficult to determine which factor guides choice behavior. We examined this issue by testing how changes in relative salience affect decision dynamics in rats performing a two-alternative forced-choice task in which rats chose between visual cues associated with high or low sucrose rewards. After initial training with high and low luminance cues, we introduced a novel cue of intermediate luminance as a "luminance shift" test. The intermediate luminance cue substituted for either the brighter or dimmer cue and had the same reward value as the cue that it replaced. We found that while rats maintained a preference for the higher-value option, the introduction of a perceptually more similar cue consistently reduced choice preference and eliminated latency differences compared to baseline. Using drift diffusion modeling, we determined that the luminance shifts primarily caused a reduction in the drift rate (the speed of evidence accumulation), reflecting increased difficulty in cue discrimination. This finding suggests that the relative salience of the options determines the efficiency of evidence accumulation in value-based decisions. Furthermore, this effect on drift rate shows a dissociation from our previous work (Palmer et al., 2024), where prefrontal cortex inactivation specifically affected only the decision threshold. Our results demonstrate that relative salience influences deliberation, with low-level perceptual features shaping the computational dynamics of value-based choice. Our findings clarify the distinct contributions of sensory input and prefrontal function in the decision process. Significance StatementThis study reveals that changes in the relative salience of visual stimuli shape the computational dynamics of value-based decisions. We trained rats to make visually guided choices and found that relative differences in the brightness of the stimuli affect how quickly the rats made decisions and how often they chose a higher-value option. Our findings, together with a recent study on the role of the prefrontal cortex in value-guided decisions (Palmer et al., 2024), suggest that separate factors influence choice dynamics in rodents: visual salience affects the speed of deliberation, while prefrontal activity regulates caution. This study helps clarify how sensory and higher cognitive variables relate to the distinct computational components of the decision process.

Post-Traumatic Stress Disorder (PTSD) commonly occurs alongside Traumatic Brain Injury (TBI), yet the chronic behavioral consequences of combined neurotrauma (i.e., PTSD and TBI) across the sexes remain unclear. Using a mouse model combining Single Prolonged Stress (SPS) as a model for PTSD and Controlled Cortical Impact (CCI) as a model for TBI, we assessed gait, anxiety-like behavior, and contextual fear learning and extinction at 2, 4, and 12-weeks post-injury. Combined neurotrauma produced early and persistent gait impairments in both sexes, delayed changes to anxiety-like behavior characterized by reduced avoidance of an anxiogenic environment, and long-lasting contextual fear recall deficits. Impaired learning was observed in males, where they demonstrated reduced fear acquisition and diminished extinction rates at later time points while females showed no deficits. Across testing and sex, peak deficits emerged at 4 weeks post-neurotrauma. Together, these findings define a sex- and time-dependent behavioral phenotype following combined neurotrauma and underscore the importance of modeling comorbidity to capture the temporal and neurobehavioral consequences of trauma exposure that more closely reflect clinical populations.

Although female rats are typically less aggressive than male rats, lactating females will vigorously defend their nests and pups against an intruder. Much attention has been directed at the consequences of this aggression on the intruder and less on the consequences for the mother and her subsequent interactions with her pups. Here, we exposed resident Sprague-Dawley dams to the resident-intruder paradigm twice daily for five consecutive days, beginning when the dam's (RES) pups were 7 days old, to assess social stress effects on maternal behavior and neurobiology. Controls were dams that had time-matched (TMC) separation from their pups but were not exposed to intruders, and naive moms which were never separated nor exposed to an intruder (CTL). We assessed the dam's subsequent behavior and interactions with her pups on Day 1 and Day 5, and Fos expression after Day 5 in select regions of the prefrontal cortex, amygdala, hypothalamus and periaqueductal gray of the midbrain. In separate cohorts, after pups were weaned, the dams underwent restraint stress and plasma corticosterone assayed. PCA analysis of the dam's behaviors identified three components: normal self-focused behaviors; nurturing behaviors and rough non-nurturing behaviors. Relative to CTL, RES dams exhibited more disrupted behaviors towards their pups, including, rough transport, stepping on pups, and flinging/tossing pups around the cage. In contrast, TMC Dams showed some, but fewer changes relative to CTL, suggesting that separation from pups alone does not account for all disrupted behavior in RES dams. The bulk of these behavioral effects occurred in the first 5-10 min after reunion with the pups and were seen on both the first and fifth day of testing. Of the brain regions examined, the prefrontal cortex was activated by both the defeat/intruder stress (RES) and separation stress (TMC), whereas the dorsal PAG was activated specifically by the defeat/intruder stress. The medial and basolateral amygdala exhibited differential neuronal activity between the RES defeat/intruder-exposed dams and the other two groups. The RES moms exhibited an insufficient adrenocortical response to acute restraint stress. The results suggest that amygdala-dPAG activity is important for dissociating disrupted maternal care in RES (due to defense of the nest against an intruder) from simple pup separation, both of which activate the mPFC. The experience of repeatedly defending the nest may induce subsequent disruptions in HPA responses. The amygdala-dPAG pathway may regulate aspects of stress and emotional regulation exhibited by mothers who defend their offspring against intruders.

Risk for opioid use disorder (OUD) is substantially heritable, yet its genetic architecture remains only partly understood. This study examined oxycodone intake in two nearly isogenic rat strains, Wistar Kyoto More Immobile (WMI) and Less Immobile (WLI), and their reciprocal female F1 offspring. The parental strains differ in depression-like behavior and substance use vulnerability, with WMI rats consuming more oxycodone than WLI controls. Voluntary consumption was measured with an operant licking self-administration protocol that delivered 60 l drug per reward. Across four experimental stages, oxycodone concentrations increased from 0.025 to 0.1 mg/ml, and session durations increased from 1 to 4 hours. Female offspring showed a parent-of-origin effect. F1 females sired by WMI fathers (WLIxWMI) displayed accelerated escalation during the transition from 1-hour to 4-hour sessions in Stage 2 and consumed more oxycodone than reciprocal WMIxWLI females across expanded-access stages. This vulnerability was associated with increased licking during the drug-unavailable timeout period. In WMI and reciprocal WMIxWLI female, consumption was regulated by the drugs subjective value, as measured by lick microstructure, during Stages 1 and 2. This relationship was absent in WLIxWMI females during Stage 2. Together, these findings suggest that paternal WMI lineage is associated with a rapid transition to high oxycodone intake and cue-directed drug seeking, and identify a parent-of-origin effect that may contribute to female vulnerability to addiction.

Relapse after treatment for various mental health disorders has been linked to tendency for reductions in responding to increase over time or following re-exposure to motivating stimuli. Here we show that, in rats, responding reduced through non-contingent outcome delivery does not recover in these ways, and that this learning depends on an intact lateral orbitofrontal cortex. These findings suggest that contingency degradation overwrites original learning which may support the development of relapse-resistant behavioural interventions.

Opioid Use Disorder (OUD) remains a prominent threat to global health. Genetic background influences the susceptibility of developing OUD, although specific genetic factors remain elusive. Rodent models that differ in susceptibility to escalation and dysregulation of opioid use are valuable tools to facilitate discovery of genetic pathways. Phenotypes associated with the development of OUD were compared in seven classic inbred rat strains (M520/N, WKY/NCrl, F344/NCrl, F344/Stm, LEW/Crl, LEW/SSNHsd, LE/Stm) from the Hybrid Rat Diversity Panel (HRDP). A two-phase self-administration paradigm was utilized to assess characteristics of the acquisition of oxycodone self-administration during daily 2-h sessions, and the escalation of oxycodone use during daily 12-h sessions. Genetic background influenced the acquisition of oxycodone self-administration as indicated by differences in the initiation of responding for oxycodone during each session and different amounts of oxycodone intake. We observed that escalation of oxycodone intake between-sessions was strain dependent, and the within-session distribution of oxycodone intake was strongly influenced by strain. The M520/N strain engaged in a unique pattern of intake, characterized by rapid initiation of oxycodone responding during the acquisition phase and a significant burst-like responding during escalation. Strain-dependent sex differences were also observed in several acquisition and escalation metrics. Of interest, burst responding was more prevalent in females of the M520/N strain compared to males. Together, these data indicate that genetic background influences not only overall oxycodone intake, but specific within- and between-session metrics that capture patterns of consumption across the substance use trajectory.

RationaleThe progression of psychostimulant abuse is associated with a shift from recreational to habitual use (R2H-shift). Because this R2H-shift can be modeled using behavioral economics, we developed a novel Behavioral Economic model for the Analysis of Self-administration Time-curve (BEAST) to obtain R2H-shift variable(s). The relationship(s) between R2H-shift variables and drug intake (under normal and/or punishment conditions) is/are unknown. Our goal was to determine if the R2H-shift variable and intake variables obtained during the initial self-administration training phase were related to 1) drug intake at that time, and subsequent drug intake under 2) normal, 3) punishment, 4) post-punishment, and 5) price-constrained conditions. MethodLong Evans rats self-administered methamphetamine (METH, males n = 16, females n = 14), sucrose (males n = 22, females n = 22) and/or saline (males n = 3, females n = 10) under FR1 for 6 h per day for 20 days to obtain 1) followed by the assessment of subsequent drug intake under different conditions (2-5 above). We obtained all variables referenced above. We determined the relationships between all variables (multivariate analysis). ResultsThere were no sex differences detected in the METH and sucrose studies. For METH and sucrose, prior drug intake levels could predict drug intake under normal/punishment but not under price-constrained conditions. The R2H-shift variable could predict drug intake under a consumption-price curve but could not predict intake under normal/punishment conditions. ConclusionsWhile related to economic demand, the recreational-to-habitual shift rate was unrelated to drug intake levels (under normal and punishment conditions).

While cognitive and behavioral manifestations of obsessive-compulsive disorder (OCD) are well known, the neuronal dynamics underlying these symptoms remain poorly understood. Theoretical work suggests that changes in the attractor dynamics of neuronal networks towards increased stability and decreased flexibility might cause behavioral and cognitive symptoms of OCD. We used chronic treatment with the D2 and D3 dopamine receptor agonist quinpirole as a rat model of the disease. In this model, we examined changes in behavioral dynamics and, in a parallel experiment, changes in organization of neuronal activity in the hippocampus and anterior cingulate cortex (ACC). At the behavioral level, we observed increased locomotion and repetitive stereotypical trajectories in quinpirole-treated rats, with frequency of repetitions increasing over the course of the session. At the level of neuronal activity, a gradual increase in the firing rate of ACC neurons within a session paralleled the dynamics of behavioral stereotypy after quinpirole treatment. In quinpirole-treated rats, we observed increased stability in the temporal organization of hippocampal neuronal firing, but no increase in the stability of the spatial organization of discharge. The increased stability of hippocampal firing was observed at both the level of single neurons and coordinated activity of neuronal pairs, and was connected to modulation of activity by theta rhythm. Studying neuronal activity changes underlying behavioral and cognitive manifestations of brain disorders is crucial for understanding and treating brain pathologies. HIGHLIGHTSO_LIDynamics of behavior and neuronal activity was characterized in rats after chronic quinpirole treatment, which is considered a model of obsessive-compulsive disorder. C_LIO_LIThe quinpirole treatment led to repetitive stereotypical trajectories, with increasing frequency of repetitions over the course of a session. C_LIO_LIThe quinpirole treatment was associated with more stable theta modulation of single-cell hippocampal firing within experimental sessions. C_LIO_LIQuinpirole increased stability in cell-pair correlations of hippocampal units within and between sessions. C_LIO_LIQuinpirole led to more stable coordination of local field potential activity between the hippocampus and anterior cingulate cortex at theta frequencies. C_LI

Alcohol use disorder (AUD) is a significant public health concern. In Canada, about 18% of individuals aged 15 or older will meet the clinical criteria for AUD at some point in their lives (CAMH, 2023). Treatment options for AUD are limited, and the high relapse rates highlight the urgent need for innovative methods to study and address AUD. Zebrafish (Danio rerio) is an emerging model for exploring the neurobiological impacts of alcohol. Previous studies have demonstrated that zebrafish respond to the rewarding effects of alcohol, but most research methods rely on passive administration, such as immersion, which does not reflect the typical routes of alcohol intake in humans. We previously showed that zebrafish can learn to self-administer drugs of abuse in small groups and conditioned animals are displaying key features of substance abuse disorders. However, group-based conditioning limits our understanding of individual drug preference and intake profile. In this study, we improved upon our previous design by establishing an individual self-administration protocol to measure voluntary alcohol intake and model alcohol use disorder. In this novel assay, individual adult fish learn to discriminate between two zones to self-administer a 5% ethanol solution. Moreover, animals conditioned in this assay can perform progressive ratio and display signs of withdrawal upon cessation of ethanol intake. These results suggest zebrafish can develop ethanol abuse-like behaviour, providing a powerful platform to study genetic predisposition and screen for therapeutic compounds.

20% of Americans are at risk for environmental circadian rhythm disruptions (CRD) due to shift work, leading to substantial negative health outcomes. However, females are especially affected with greater vulnerability for substance use (SU) and adverse outcomes associated with pregnancy, including for offspring at birth and later in life. In mice, prenatal CRD (pCRD) recapitulates these risks, but it is unknown whether pCRD affects SU in mature offspring. To investigate this, C57BL/6J dams were disrupted by reversing the light/dark cycle during gestation. Following pCRD, reward- (cocaine conditioned place preference, intravenous self-administration) and mood-related behaviors (open field, elevated plus maze, light/dark box, forced swim) were measured in adult offspring. Adult female offspring of dams exposed to CRD developed an anhedonic-like phenotype with decreased food self-administration, cocaine intake and reinforcing properties of cocaine. Opposingly, pCRD male offspring showed a SU-like phenotype with increased cocaine preference, higher order food self-administration and cocaine reinforcement. Interestingly, these divergent behavioral outcomes were not specific to reward. While female pCRD mice showed increased anxiety-like behavior, pCRD males showed decreased anxiety/increased risk-taking behavior, as well as decreased immobility in the forced swim test. Rhythms in corticosterone were also sex-specifically affected by pCRD. These results suggest that pCRD may predispose individuals to distinct psychiatric disorders based on sex with mood disorders developing in females and SU disorders developing in males. By better understanding how disrupted rhythms during pregnancy affect behavior in adulthood, we can develop novel therapeutic approaches for SU and mood disorders in adults.

IntroductionAdolescence is a sensitive developmental period during which chronic stress can induce lasting adaptations in corticolimbic circuits involved in stress regulation, cognition, and emotional behavior. We examined the long-term behavioral, endocrine, and molecular consequences of adolescent chronic variable stress (CVS) in male and female rats, focusing on the infralimbic cortex (IL) and basolateral amygdala (BLA) MethodsSprague Dawley rats of both sexes were exposed to CVS during late adolescence and evaluated in adulthood after an extensive recovery period. Behavioral testing included cued fear conditioning and extinction recall, delayed spatial win-shift, novel object recognition, Morris water maze, three-chamber social behavior, and passive avoidance. HPA-axis reactivity to acute restraint was assessed. Targeted qPCR was used to measure stress-related gene expression in the IL and BLA immediately after stress or after a 5-week recovery period ResultsAdolescent CVS did not cause generalized cognitive impairment, but instead produced selective, sex-specific effects. Females had reduced HPA responses to acute stress and mild deficits in delayed spatial win-shift performance, together with long-term IL changes in genes related to adrenergic signaling, plasticity, and GABA clearance. Males showed enhanced Morris water maze probe retention, weaker novel object discrimination, altered passive avoidance with marked inter-individual variability, and enhanced social preference. At the molecular level, males exhibited long-term upregulation of Fkbp5 in IL and downregulation of PACAP, 1D adrenergic receptor, and proenkephalin in BLA, whereas females showed delayed PACAP upregulation in BLA DiscussionAdolescent CVS induces persistent, sex- and region-specific recalibration of corticolimbic function, supporting distinct patterns of vulnerability and resilience, rather than uniform stress pathology.

Behavior arises from the complex interplay between an organisms nervous system, its genetic makeup, and the environment. High-resolution, high-throughput behavioral quantification is essential for dissecting biological function and the effects of genetic perturbation, but automated analysis remains challenging. Here, we present Autobehaver, an automated behavioral analysis pipeline based on a low-cost, high-throughput recording platform that captures videos of individual Drosophila. From each video, we extracted keypoints and used a custom Transformer to assign frame-wise behavior and orientation labels. We then converted these predictions into high-dimensional per-animal feature vectors and trained XGBoost ensembles to classify animals and identify the features that separated groups. By applying SHAP analysis to the classifier ensemble, we identified the behavioral features most informative for distinguishing groups of flies. We demonstrated the approach in several ways. First, we recovered known behavioral changes associated with heat-activated dTrpA1 activity in specific neural circuits. Second, we detected age-associated behavioral changes consistent with gradual impairment of locomotor and climbing ability. Finally, we used Autobehavers classifier ensemble to place animals with intermediate phenotypes along a behavioral axis and used feature-importance analysis to reveal the behavioral features underlying those intermediate states. Together, Autobehaver provides an interpretable framework for quantitative behavioral phenotyping and comparative analysis of complex genotypes.