Physiology & Behavior

Purpose Postprandial sedentary behavior is associated with negative health effects and constitutes a large part of daily life in modern society. This study investigated how the timing of physical activity after eating influences glucose levels, cerebral and muscle oxygenation, cognitive performance, and well-being during subsequent sitting. Methods In a four-armed randomized crossover trial, healthy adults consumed four standardized meals separated by 48-hour washout periods. Each meal was followed by 2 hours of sitting combined, in random order, with one of four interventions: (1) sitting only, (2) 15 minutes of moderate intensity cycling immediately after eating, (3) 15 minutes of cycling 20 minutes after eating, or (4) three workload-matched five-minute cycling bouts during sitting. Interstitial glucose (continuous glucose monitoring), cerebral and muscle oxygenation (Functional near infrared spectroscopy), cognitive performance (Stroop test), heart rate, blood pressure, and subjective ratings were assessed every 30 minutes. Data were analyzed using repeated-measures ANOVA. Results Twenty participants (mean age 27.1{+/-}10.3 years, 12 females) completed the study. Cycling immediately after eating reduced mean glucose levels during postprandial sitting, while both 15-minute cycling bouts increased cerebral oxygenation. All active conditions enhanced muscle oxygenation. Heart rate and arousal increased with delayed cycling and active breaks. No effects were observed for blood pressure, cognitive performance, focus, or well-being. Conclusion A short bout of physical activity immediately after eating reduces postprandial hyperglycemia and improves brain oxygenation during sitting, whereas delayed activity and brief breaks increase physiological activation without cognitive or perceptual benefits.

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.

Voluntary physical activity is a highly motivated behavior with important implications for physical and mental health, yet the neural and endocrine mechanisms underlying motivation to exercise remain poorly understood. In contrast, motivation for sugar/palatable foods, drugs, and sex has been extensively characterized using operant paradigms. Here, we describe a novel progressive ratio operant task to measure motivation to run, independent of running ability. Using female Long Evans rats, which exhibit robust voluntary running behavior, we validated this paradigm by applying a manipulation well known to enhance the motivation to run: calorie restriction. Calorie-restricted animals exhibited increased operant responding to gain access to a running wheel, thus demonstrating heightened motivation for exercise. More specifically, calorie-restricted rats completed more ratios, reached a higher breakpoint in the progressive ratio task, ran more, and spent more time in the operant chamber. We did not observe any effects of calorie restriction on the estrous cycle or steroids (e.g. corticosterone, testosterone) in the blood or brain. Importantly, our task dissociates the motivational drive for physical activity from the ability to perform the physical activity itself, providing a new paradigm for studying the neural and endocrine mechanisms that regulate exercise motivation.

Considerable evidence suggests that the motivational control of instrumental action depends on incentive learning; i.e., on the opportunity to learn how the value of the consequences or outcome of an action, (e.g., a specific food) varies under different motivational conditions (e.g., under different degrees of hunger). The current study investigated whether learning the values of high-protein and high-carbohydrate rewards under different degrees of protein and carbohydrate appetite is also necessary for these nutrient-specific appetites to exert control over instrumental performance. Experiment 1 gave differing consummatory experience to whey protein and polycose carbohydrate outcomes under protein and carbohydrate appetite and found that, without the opportunity for incentive learning, the performance of actions earning these outcomes was insensitive to a shift in appetite. However, once the opportunity for incentive learning was provided, the rats increased their instrumental performance on a lever that earned the whey outcome relative to the polycose lever when protein hungry and on the polycose lever relative to the whey lever when carbohydrate hungry. Experiment 2 assessed how these nutrient-specific states exerted this control; whether, once learned, nutrient values were immediately controlled by nutrient appetite or whether this was based on conditional control acquired during experience with the outcomes under different nutrient appetites. We found that exposure to an outcome under a single nutrient-specific state was not sufficient to establish state-specific control. Instead, establishing the conditional control of outcome value required exposure to both the whey and polycose outcomes under both protein and carbohydrate appetites.

Of the three dietary macronutrients, protein plays an especially pivotal role in physiological functions. Nevertheless, the behavioural control of protein intake is poorly understood. In this study, we used Feeding Experimentation Devices (FED3s) to examine the structure of ingestive behaviour in mice given access to diets varying in protein content. Adult C57BL/6NRj mice were contact-housed in pairs in custom-made cages with perforated dividers, each having access to an individual FED3 unit. Mice were given ad libitum access to either 20 mg control, non-restricted (NR) pellets (20% casein) or 20 mg protein-restricted (PR) pellets (5% casein) from FED3s on free-feeding mode. Each pellet retrieval event was timestamped ~24 h/day. All mice experienced both diets for 7 days with order of diet presentation counterbalanced (i.e., NR[->]PR and PR[->]NR). Analysis of dynamics of pellet intake per day revealed that mice that were initially protein-restricted first showed a decrease in pellet intake before increasing on later days and exhibiting a persistent high level of intake once non-restricted diet was available. The group that was initially non-restricted exhibited a blunted response to the same diet manipulation. In addition, we clustered pellet retrieval data into discrete clusters of feeding events and used a mathematical approach to determine the boundary of meals (2-5 pellets), separated from "snacks" (1 pellet) and "feasts" (>5 pellets). We identified alterations in meal patterning in response to diet manipulation with protein restriction increasing "snacking" and leading to increased meal number, and reduced meal size. Moreover, restored access to NR diet, elicited "feasting". These effects depended on the sequence of diets the mice experienced, such that the effects were stronger in initially protein restricted mice compared to those initially non-restricted. In summary, our findings show that manipulation of dietary protein levels affects meal patterning in adult mice.

Unpredictable and insufficient access to food, known as food insecurity, is associated with the development of obesity. However, causal mechanisms underlying this paradoxical relationship remain poorly understood. Using a rat model of food insecurity, this study investigated whether food insecurity causes dysregulated feeding behaviours, specifically impaired gut signal sensitivity and enhanced cue-driven appetitive responses. Adolescent female rats were assigned to receive either ad libitum chow access (Food secure), 90% caloric restriction (Food restricted) or unpredictable quantity and timing of food access (Food insecure), for 4 weeks. After which, rats were returned to an ad libitum chow diet for the remainder of the study. To examine gut signal sensitivity, we measured the effects of cholecystokinin (CCK) on 10% sucrose intake. To examine cue-driven feeding behaviours, we used Pavlovian appetitive conditioning and measured appetitive responses towards a food-predictive cue. Results showed that prior food insecure rats were less sensitive to the intake inhibitory effects of CCK and exhibited enhanced cue-induced appetitive behaviours, when compared to food secure and food restricted groups. Anxiety-like behaviours or learning and memory was not different between groups. At the end of the study, adolescent caloric restriction resulted in reduced fat mass, plasma leptin levels and body weight when compared to food secure, but not food insecure rats, suggesting that adolescent food insecurity somewhat overcame these metabolic effects. Taken together, our findings suggest that adolescent food insecurity impaired gut signal sensitivity and heightened food cue sensitivity, which may cause enduring metabolic and behavioural adaptations that promote overeating and weight gain.

Study Objectives To develop and initially validate the Circadian Disruption Index (CDI), a self-report measure of circadian disruption, and obtain preliminary evidence of its responsiveness to circadian health education. Methods In Study 1, 244 participants completed a 22-item CDI version and external measures. The sample was randomly divided for exploratory and confirmatory factor analyses. Internal consistency, external associations, and discrimination of poor sleep quality were examined. In Study 2, 72 postgraduate students completed the CDI before and 1 week after a 16-hour circadian health education program in an uncontrolled pre-post design. Results Analyses yielded a 15-item, three-factor structure comprising rhythm stability and light exposure, behavioral habits and diet, and sleep quality and subjective complaints. Total-score internal consistency was acceptable (Cronbach's = 0.871). Confirmatory factor analysis showed a comparative fit index of 0.902 and a root mean square error of approximation of 0.072, although the Tucker-Lewis index was 0.882. CDI scores correlated with sleep quality, chronotype, corrected midsleep on free days, depression, and anxiety, but not social jetlag. The area under the curve for poor sleep quality was 0.807 (95% confidence interval, 0.753-0.862), with an exploratory cutoff of [≤] 23. In Study 2, CDI scores decreased from 22.26 to 19.88 (p = 0.002; Cohen's dz = 0.36). Conclusions The CDI demonstrated satisfactory internal consistency, a meaningful multidimensional structure, and responsiveness to short-term changes following circadian health education, supporting its potential utility for assessing circadian disruption and monitoring circadian-related behavioral changes.

Standard rat housing may impede species-typical behaviors and impact rat welfare and research outcomes. This research investigated the effects of housing on behavioral and physiological outcomes of rats through the use of modified large animal cages for housing, and was conducted in two studies. Study A: 70 Sprague Dawley (SD) rats (34 males, 36 females; 5 wk old) were randomly assigned to standard polycarbonate shoebox cages (C: 733.9cm2) or modified stainless steel primate cages (T: 10,416cm2) for 18 days. In Study B: 48 SD rats (24 males, 24 females; 7.5 wk old) were held in T housing for 90 days to assess long term impacts. All rats received gentle handling for 15s 3x/week. Rats were assessed for body weight, anxiety-like behavior in an elevated plus maze, response during a voluntary human approach test, and overall home cage behavior, posture, and space usage. Data were analyzed using generalized linear mixed models, with sex and treatment as fixed effects, and cage as the random effect. The results of study A suggest that the modified large animal cages (T) had positive impacts on rat behavior and welfare. T rats were less anxious (P=0.038) and more active (P<0.0001) and explorative (P=0.0003) compared to C rats. In both groups, activity levels declined towards the end of the 18-day study period (P<0.0001). For study B, similar patterns were observed, with rats becoming more inactive (P<0.0001) over 90 days. However, rats spent significant time on elevated shelves in T housing, which increased throughout the study (P<0.0001), suggesting continued use of the resources the housing provided. In both studies, there were no differences in latency to approach humans (P>0.05), but T rats spent less time in contact with human handlers, suggesting differences in motivation to interact with humans that should be explored further.

The lactational period requires substantial metabolic and behavioral adaptations, and more than 70% of mothers report weight concerns and attempt weight loss by four months postpartum. Nevertheless, how distinct restrictive paradigms during lactation alter maternal behavior, and the extent to which associated neurochemical changes modulate these behaviors, remains poorly understood. In the current study, we modeled restrictive diets in lactating rats to evaluate caregiving behavior and its relationship to amygdalar redox status. Intermittent fasting (IF) and caloric restriction (CR) administered to lactating Wistar dams from postpartum day 0 to day 28 impaired maternal care, evidenced by delayed pup retrieval, reduced nest building, and decreased nursing frequency relative to ad libitum-fed controls. Both diets reduced body and adipose tissue weight, and energy efficiency. IF and CR increased impulsivity-like phenotype: CR doubled open-arm exploration in the elevated plus maze; IF and CR increased center-zone exploration in the open field by three- and two-fold, respectively; IF doubled time in the light-dark box light compartment. A composite maternal behavioral score showed impairment in dams in both IF and CR groups. At the neurochemical level, both diets reduced amygdalar superoxide dismutase activity, which correlated negatively with the maternal behavioral score. Both restrictive diets produced an underweight phenotype with weakened dam-pup interactions and increased impulsivity. These behavioral changes co-occurred with amygdalar redox imbalance, which correlated with the severity of maternal impairment. Overall, the study refines understanding of the nutritional and behavioral consequences of dietary restriction in lactation and implicates disrupted redox homeostasis as a plausible mechanism.

Background: Prolonged unsupplemented spiritual fasting (USF), complete caloric abstinence motivated by spiritual practice, is undertaken by many communities worldwide, yet its physiological consequences remain poorly characterized. No prior study has documented continuous real-time monitoring during free-living fasting beyond 10 days. Methods: We conducted a self-controlled observational study of 23 experienced Jain practitioners undergoing USF. Seventeen completed at least 8 days of fasting (11 completed eight days, six continued to 30 days); six discontinued early. Continuous glucose monitoring (CGM) and blood biomarkers at baseline (Day-0), post-fasting (Day-9), and 60-day follow-up (Day-69) were obtained. Mood was assessed daily using PANAS. Within-participant comparisons used both parametric and non-parametric t-tests. Results: CGM revealed near-complete suppression of glycaemic variability within 24-48 hours of fasting onset, sustained throughout with no clinical hypoglycaemia in either cohort. Blood biomarkers showed transient perturbation during fasting -- including rises in hepatic enzymes, bilirubin, uric acid, creatinine, and lipid fractions -- broadly reversible by follow-up (Day-69). hsCRP rose during fasting then fell below baseline at follow-up (5.52{+/-}13.67 to 3.68{+/-}13.18 mg/L, p=0.034). HDL significantly rose above baseline (45.71{+/-}112.32 to 48.97{+/-}111.19, p=0.045) and LDL similarly declined below baseline (122.33{+/-}132.10 to 106.96{+/-}131.62 mg/dL, p=0.035); and then both significantly improved by follow-up. Thyroid axis suppression fully normalized by follow-up. Psychological wellbeing was maintained throughout. Conclusions: Extended USF produces a safely reversible pattern of acute physiological adaptation with net cardiometabolic benefit. Absence of clinical hypoglycaemia during 30-day water-only USF, documented here for the first time with CGM, provides empirical grounding for future controlled trials.

Curiosity, a key driver of exploration and learning, is reinforced by reward-related neurochemical systems, yet the role of the opioidergic system in modulating this behavior remains unclear. Music, as a highly rewarding stimulus, offers a unique context to investigate the neurochemical basis of curiosity, particularly the unexplored role of opioids in music-driven exploration. To fill this gap, we performed a double-blind within-subject pharmacological design, in which 26 participants received, in two different sessions, either a placebo or the opioid antagonist naltrexone. During each session, participants engaged in a music exploration/exploitation trade-off paradigm designed to assess their willingness to pay for exploring unfamiliar electronic music. Using logistic regression mixed-effects models, we found that while naltrexone did not affect overall curiosity ratings, it significantly reduced exploratory behavior in states of heightened curiosity. These findings suggest that the opioidergic system plays a critical role in regulating the relationship between curiosity and exploration, particularly in the context of novel and rewarding stimuli like music. Overall, the present research provides new and compelling evidence on the important relationship between curiosity and exploration and its regulation with the opioidergic neurotransmitter subsystem. Significance StatementThe present research aimed to advance our understanding of the neurochemical mechanisms underlying curiosity and information seeking. In our study, we employed a pharmacological design to examine the role of the opioidergic system in music-related exploration. Using a novel music exploration/exploitation paradigm, we found that while naltrexone, an opioid antagonist, did not affect baseline curiosity ratings, it markedly reduced exploratory behavior during high-curiosity states in the presence of potential monetary losses. These results provide new evidence that opioidergic modulation plays a critical role in regulating curiosity-driven exploration. This new evidence might be relevant in the future for better understanding how neurochemical systems shape learning, motivation, and affective responses in complex cognitive domains such as music.

The circadian system evolved under natural light-dark cycles, while modern humans spend much of their time indoors under electric lighting that differs substantially from daylight in intensity, spectral composition, and temporal structure. How such lighting environments influence circadian system has not been systematically examined in a diurnal animal model under ecologically relevant conditions. In this study, we used the diurnal Nile grass rat (Arvicanthis niloticus) to assess daily locomotor rhythms across four lighting conditions designed to approximate common human exposure scenarios: rectangular daylight (D65-R; [~]5,600 lux), semi-sigmoidal daylight mimicking natural intensity dynamics (D65-S; matched peak intensity with [~]50% lower cumulative energy), fluorescent indoor light (F12; [~]150 lux), and fluorescent light supplemented with a one-hour midday daylight pulse (F12+D65-P). Using a within-subject design (n = 8), male grass rats were housed under each condition for two weeks. D65-R produced the highest daytime activity levels and the strongest day/night activity ratio, consistent with robust circadian entrainment. Despite matching peak intensity, D65-S did not yield comparable circadian outcomes, indicating that cumulative photon exposure, rather than peak intensity alone, contributes to entrainment strength. Notably, the addition of a one-hour midday daylight pulse (D65-P) partially increased circadian amplitude under otherwise fluorescent conditions, with higher periodogram amplitude relative to F12 alone. A separate cohort of males was exposed to D65-R or F12 for six weeks (n = 10/condition) to assess physiological outcomes, including metabolic and reproductive measures. Compared with the D65-R group, F12 group showed higher diabetic rate (10% vs. 40%) and reduced sperm mobility (45{+/-}6 vs. 19{+/-}1 %), consistent with potential downstream correlates of circadian rhythm disruption. Together, these findings demonstrate that lighting conditions characteristic of indoor environments produce weaker circadian organization than daylight-equivalent lighting in a diurnal rodent, which underscore the importance of light quality in shaping circadian rhythms and downstream physiological processes.

The cortisol awakening response (CAR) marks the transition from rest to wake phase by a sharp increase in cortisol levels upon awakening in the morning. This increase may assist in cognitive and behavioral awakening, but its function is not fully understood yet. In this pilot study we aimed to provide first data on the influence of immune system activity on the CAR. Thereby, a within-subject analysis approach was applied to avoid confounding by between-subject bias and improve inference of the results. Three healthy subjects collected their overnight urine for analysis of neopterin (Th1 immune activation marker) and sampled saliva at 0, 30, and 45 minutes after awakening in the morning for cortisol determination and CAR estimation. Additionally, subjects wore an EEG-headband overnight for objective determination of the awakening timepoint. Random-effects models were computed to estimate the effect of overnight neopterin on the CAR. There was a significant positive effect of overnight neopterin levels on the CAR, indicating that overnight Th1 immune activation may predict the dynamic increase of cortisol in the morning, with higher immune levels leading to a stronger CAR. These results provide first evidence for the immunological awakening hypothesis and a potential role of the CAR in the maintenance of circadian immune rhythms, but given the small number of participants, findings should be interpreted as exploratory.

Circadian rhythms are crucial to biological functions, and cognitive functions such as attention, choice, and preference-related behaviors are modulated by circadian rhythms and disrupted in mood disorders such as Seasonal Affective Disorder (SAD) and Major Depressive Disorder (MDD). These neuropsychiatric diseases can be induced or worsened by alterations to daily light patterns and can also be treated with circadian-timed bright-light therapy, suggesting modulatory effects of light brightness on mood and behavior. While most laboratory rodents are nocturnal, the Nile grass rat (Arvicanthis niloticus) is diurnal, offering a unique model to study light modulation effects relevant to humans. In this work, we track daily activity in male and female grass rats under varied lighting for several weeks, revealing sex-specific circadian patterns and responses. These findings establish a foundation for mechanistic studies of light effects on mood-related brain circuits in diurnal animals.

IntroductionAnorexia nervosa (AN) is more prevalent in women than men, although rates in men are rising. Animal models can provide insight into whether this differential prevalence is rooted in biological mechanisms, but prior studies have yielded conflicting findings. Using the activity-based anorexia (ABA) model, we previously demonstrated that female mice exhibit distinct vulnerable and resilient phenotypes. Here, we use this phenotypic framework to investigate sex differences in ABA susceptibility. MethodsWe tested young adult male C57BL/6N mice using the same ABA protocol used to test age-matched C57BL/6N females. Individual differences in daily bodyweight, food intake, water intake, and wheel running were analyzed and compared across sexes. ResultsMales exhibit the same vulnerable and resilient phenotypes as females, with no sex difference in the proportion of mice exhibiting each phenotype or the repertoire of behaviors characterizing them. In both sexes, vulnerable mice exhibit catastrophic weight loss driven by excessive light cycle running, while resilient mice exhibit weight stabilization driven by adaptive changes in consumption. Running during the feeding window revealed that vulnerability is not driven by a decision to run instead of eat in either sex. ConclusionsABA models adaptive and maladaptive responses to food restriction in both sexes. Behavioral responses to starvation are similar across sexes, suggesting that sex differences in AN prevalence may be driven by stronger sociocultural pressures faced by women to lose weight.

Ramadan fasting represents a natural model of prolonged daily intermittent fasting associated with metabolic and circadian alterations. This study investigated longitudinal changes in intracortical excitability across pre-, mid-, and post-Ramadan timepoints in healthy adults observing Ramadan fasting. Thirty fasting participants underwent paired-pulse transcranial magnetic stimulation at three timepoints (pre-, mid-, and post-Ramadan). A non-fasting control group (n = 11) was assessed at pre- and mid-Ramadan. Conditioned motor-evoked potentials were recorded at interstimulus intervals of 2-10 ms and normalized to unconditioned responses. A linear mixed-effects model assessed effects of Timepoint and interstimulus interval (ISI). Secondary outcomes included blood glucose, cognitive performance, sleep duration, and reaction time. A significant main effect of Timepoint (p < 0.001) indicated longitudinal modulation of intracortical excitability, with increased MEP ratios at mid-Ramadan and partial persistence post-Ramadan. The ISI effect confirmed the inhibition-facilitation gradient (p < 0.001). The Timepoint x ISI interaction was not significant (p = 0.566), indicating a global shift in excitability without ISI-specific modulation. Blood glucose and sleep duration decreased significantly at mid-Ramadan. Ramadan fasting is associated with a time-dependent increase in intracortical excitability, most appropriately interpreted as a generalized shift rather than selective modulation of inhibitory or facilitatory circuits. These changes occur in the context of concurrent metabolic and sleep alterations and may reflect combined influences of fasting-related metabolic state and reduced sleep duration; however, these factors cannot be disentangled within the present design.

Major international sporting events frequently impose exogenous demands that challenge adult circadian rhythms, often leading to the misalignment of sleep-wake cycles and social schedules. This cross-sectional study investigated the impact of the FIFA 2022 World Cup on adult sleep patterns to assess the prevalence and determinants of tournament-associated circadian disruption. Through an online survey, we captured data on sleep duration, timing, and subjective quality from a diverse adult population using Pittsburgh Sleep Quality Index (PSQI) score. The results indicate that 81.3% had high problematic sleep according to PSQI scores, while only 9% perceived that their sleep pattern was impacted by watching matches during the tournament. While 83.7% of the participants had low or mild anxiety according to GAD-7 scores, we found that GAD-7 scores correlated significantly with PSQI scores. Married participants had significantly lower PSQI scores (RR 0.856, p = .005), while those who reported that their sleep hours had changed during the tournament had significantly higher PSQI scores (1.180, P-value <0.001). Males reported a significantly high impact of the tournament on their sleep (OR 2.622, P-value <0.001). In conclusion, our data demonstrate a discrepancy between self-perception of sleep quality and self-rated assessment by PSQI scores, as well as the substantial impact of major international sporting events on adult sleep hygiene. The results provide data-driven insights helpful in evaluating potential circadian risks and informing public health strategies for major sporting events such as the FIFA world cup.

Adolescence is a sensitive period during which unhealthy diets may shape metabolic health and cognition. Diets high in fat and sugar have been linked to obesity, impaired glucose regulation and hippocampus-dependent deficits, but the exposure duration required to affect cognition remains unclear. This study examined whether adolescent-onset exposure to a high-fat high-sucrose (HFHS) diet induces metabolic dysfunction and impairs object-based memory, spatial working memory and spatial pattern separation in male Long Evans rats. Rats were assigned to a control or HFHS diet at four weeks of age and remained on this diet into adulthood. Basal blood glucose was assessed monthly and home-cage behaviour using 48-hour LABORAS recordings. Cognitive testing started after 10 weeks of diet exposure, when basal glucose was elevated in HFHS-fed rats. Object displacement and novel object recognition were used in short open-field test settings, whereas touchscreen-based trial-unique nonmatching-to-location testing (TUNL) assessed spatial working memory and pattern separation across repeated operant sessions. Finally, glucose (in)tolerance and tissue weights were measured. HFHS diet exposure produced a metabolic phenotype, including increased body weight, elevated basal glucose, impaired glucose tolerance and increased liver and gonadal white adipose tissue weights. The diet also altered the general behavioural repertoire, with increased immobility and grooming and reduced rearing. HFHS-fed rats did not differ from controls in object displacement or novel object recognition performance. In the touchscreen task, both groups acquired the task at a comparable rate. Long-delay and spatial separation challenges reduced performance as expected, confirming task sensitivity, but did not reveal diet-related impairments. These findings show that adolescent-onset HFHS diet exposure induces metabolic dysfunction but does not necessarily produce detectable cognitive impairment when behavioural testing starts after 10 weeks of exposure. Longer exposure or advanced diet-induced inflammatory or neurobiological alterations may be required to reveal cognitive consequences.

Social behavior is a fundamental phenotype across vertebrates. Zebrafish (Danio rerio) have emerged as a valuable translational model for investigating the neurobiological mechanisms underlying sociability, particularly due to their robust shoaling behavior and experimental tractability. However, the literature presents issues of reproducibility and inconsistent findings regarding the modulation of social preference and shoal cohesion in adult zebrafish. We conducted a systematic review and meta-analysis to synthesize studies evaluating the effects of pharmacological interventions that modulate the central nervous system and stress-related interventions on social behavior in adult zebrafish and, when available, anxiety-like behavior. The literature search was performed in three databases (Embase, PubMed, and Web of Science), followed by a two-step screening process based on inclusion/exclusion criteria. The included studies underwent extraction of qualitative and quantitative data, as well as risk of bias assessment. Interventions from the included studies (n = 108) were categorized according to their nature, mechanism of action, and/or therapeutic purpose, resulting in seven, four, and five meta-analyses for social preference, shoal cohesion, and anxiety-related tests, respectively. Ethanol, NMDA antagonists, pro-dopaminergic agents, and stress-related interventions decreased social preference, while stress-related interventions increased shoal cohesion. The fact that stress produced opposite effects suggests that these paradigms measure distinct sociability constructs, or perhaps are differentially modulated by confounding factors, like anxiety for example. The studies presented high heterogeneity, with prediction intervals compatible with effects in both directions, as well as methodological limitations and deficiencies in data reporting, as evidenced by the risk of bias assessment. These findings emphasize the need for well-designed new studies to validate the findings and expand the evidence on interventions that currently lack sufficient studies for quantitative synthesis.

Running can improve mood, but the proximal processes linking exercise-induced bodily changes to subjective affective changes remain unclear. Interoception, the sensing and interpretation of internal bodily signals, is central to how bodily states are integrated into emotional experience and may therefore link exercise-induced bodily changes to mood. Here we tested whether interoception links acute running to mood improvement. Twenty-seven healthy young adults completed a crossover experiment consisting of a 15-min moderate-intensity treadmill running condition and a seated rest condition, each performed on separate days. Interoceptive accuracy was assessed using heartbeat counting and tapping tasks. Present-moment interoceptive sensibility was monitored using a state-adapted Body Perception Questionnaire, and mood state was monitored using the Profile of Mood States. Compared with seated rest, running reduced total mood disturbance and tension-anxiety, increased vigor-activity, and enhanced heartbeat-signal discrimination and interoceptive sensibility. Running-related increases in interoceptive sensibility were associated with greater reductions in total mood disturbance and tension-anxiety. Mediation analyses further indicated that changes in interoceptive sensibility partially mediated the effect of running on total mood disturbance, with weaker evidence for tension-anxiety. These findings suggest that enhanced interoceptive sensibility may represent one proximal process through which acute running improves mood states.