Search Results (228)

In quantum time (QT) schemes, time is promoted to a degree of freedom, allowing Lorentz covariance to be made explicit for single particles. We ask whether this can be lifted to QFT so that Lorentz covariance becomes manifest at the Hilbert-space level, rather than being hidden as in the standard canonical formulation. We address this question by proposing a second-quantized approach in which the elementary particle is the QT particle itself, leading naturally to the notion of spacetime field algebras and of quantum action. We show, however, that a naive many-body construction runs into inconsistencies. To pinpoint their origin we introduce a classical counterpart of the second-quantized formalism, spacetime classical mechanics (SCM), and prove a no-go theorem: Dirac quantization of SCM collapses back to standard QFT and therefore hides covariance. We circumvent this problem by presenting a quantum-action-based quantization that yields a spacetime version of quantum mechanics (SQM), making covariance manifest for (interacting) QFTs. Finally, we show that this resolution is tied to a genuine spacetime generalization of the notion of a quantum state, required by causality and closely connected to recent “states over time” proposals and, in dS/CFT–motivated settings, to microscopic notions of timelike entanglement and emergent time. Full article

We establish a general no-go theorem demonstrating that all traversable wormhole configurations in Unimodular Gravity necessarily require exotic matter. The proof relies solely on the geometric flaring-out condition, b′(r₀) ≤ 1, which directly implies that ρ(r₀) + p_r(r₀) ≤ 0 at the throat. This condition represents a violation of the Null Energy Condition and, consequently, of the Weak and Strong Energy Conditions, independently of the particular choice of shape function, redshift function, or equation of state. This result holds for both tidal and zero-tidal-force configurations, showing that the requirement of exotic matter is a fundamental geometric consequence of the traversability condition rather than an artifact of specific solution choices. Therefore, Unimodular Gravity shares this fundamental constraint with General Relativity. Full article

Background: Obstructive sleep apnea (OSA) is associated with slower response speed, yet conventional severity classification based on the apnea–hypopnea index (AHI) shows limited ability to predict cognitive outcomes. The AHI aggregates distinct pathophysiological processes, including intermittent hypoxemia and sleep fragmentation. Within emerging precision sleep medicine frameworks, disentangling these mechanisms is critical for improved phenotyping and personalized risk assessment. This study aimed to replicate prior findings using a Go/No-Go Continuous Visual Attention Test (CVAT) and to identify the most informative polysomnographic predictor of attentional performance in OSA. Methods: In this cross-sectional study, participants underwent full-night type I polysomnography and the CVAT. After exclusions, 84 patients with OSA and 22 polysomnographically normal controls were analyzed. The sample sizes for mean differences and correlational analyses were adequate. Attentional performance was indexed by standardized reaction time (RT), referenced to a normative database (n = 1244). Within the OSA group, linear regression with backward elimination evaluated hypoxemia and sleep fragmentation metrics. Results: Patients with OSA demonstrated significantly slower RTs than controls (p = 0.005). Within OSA, the AHI was not associated with attentional performance (p = 0.398). In the final regression model, sleep stage shifts—reflecting sleep–wake instability—emerged as the sole independent predictor of attentional slowing (β = 0.27, p = 0.013), whereas all hypoxemia indices were excluded. Conclusions: Sleep stage instability represents a cognitive vulnerability marker in OSA, independent of respiratory events. Integrating fragmentation metrics into precision sleep medicine models may enhance individualized phenotyping, identify patients at higher neurocognitive risk, and inform targeted interventions focused on stabilizing sleep architecture rather than relying solely on the AHI. Full article

Background and Objective: Adolescent bipolar disorder (BD) has substantial symptom overlaps with other psychiatric disorders. Identifying its distinctive candidate neuroimaging markers may be helpful for exploratory early differentiation and to inform future translational studies after independent validation. Methods: This cross-sectional study enrolled adolescents with BD and age- and sex-matched healthy controls. Assessments included clinical/behavioral scales and an emotional Go/NoGo task-based fMRI (Go trials require a response; NoGo trials require response inhibition) acquired across three mood states (depression, mania, and remission) and matched controls. We applied several conventional machine learning classifiers to task-fMRI data to classify BD versus healthy controls and to identify the most relevant neuroimaging predictors. Results: A total of 43 adolescents with BD (15 in remission, 11 with depression, and 17 with mania) and 43 matched healthy controls were included. Under the Go − NoGo condition, activation-derived features in the remission state showed the strongest discrimination, with RF achieving the best performance (accuracy = 94.29%, AUC = 98.57%). These findings suggest that task-evoked functional alterations may remain detectable during remission. In addition, activation patterns in regions within the limbic system, prefrontal cortex, and default mode network were significantly correlated with clinical scales and behavioral measures implicating these regions in emotion regulation and cognitive functioning in adolescents with BD. Conclusions: This study showed that adolescents with BD during remission without manic and depressive symptoms may still have aberrant neural activity in the limbic system, prefrontal cortex, and default mode network, which may serve as a potential candidate neuroimaging signature of adolescent BD. Full article

This study examined how negative emotions influence three core components of cognitive control, inhibition, updating, and shifting, as assessed through a Go/No-Go, 2-back, and set-switching task, respectively. Participants performed these three tasks under both negative and neutral emotional conditions. Negative emotions led to slower response times on false-positive trials, suggesting increased interference during inhibitory demands rather than a direct impairment of inhibition. In the 2-back task, accuracy decreased on Non-Match trials under negative emotions, indicating difficulties in updating working memory and disengaging from irrelevant information. In the switching task, participants showed higher error rates under negative emotions regardless of trial type, pointing to a broader decline in performance when cognitive flexibility is required. Correlation analyses indicated that emotion-related effects were associated between updating and shifting, but not with inhibition, suggesting that negative emotions preferentially affect partially overlapping control processes depending on their cognitive demands. These findings highlight that the impact of negative emotions is not uniform across executive functions and underscore the importance of investigating emotion–cognition interactions across multiple domains within individuals. Full article

In the microinjection molding process, continuous monitoring is important for optimization of the process and control. In microfluidic or lab-on-chip devices, defective microfeatures can compromise biological assays and diagnostic results, and therefore, the quality of these features is a critical issue. Microfeatures can be inspected using advanced inspection and microscopic techniques, but these are expensive, time-consuming, and difficult to use for full-scale production. We present here a new technique for quality control of microfeatures, which uses the filling of a controlled microcavity inside or outside the molded part as a quality control tool for filling microfeatures. Micro gaps (checkpoints) are used as an indicator of microfeature filling. Two micro gaps can be used for filling (checkpoints) as a Go/No-Go gauge. Full article

Background and Objectives: Interventions targeting the gut–brain axis offer potential for mitigating Subjective Cognitive Decline (SCD), a critical window for Alzheimer’s prevention. This study evaluated the effects of a novel probiotic supplement, ExoBDNF, on cognitive function, sleep, and emotional distress in adults with SCD. Materials and Methods: In this 9-week open-label study, participants received ExoBDNF supplementation. Efficacy was assessed using the SCD-Questionnaire (SCD-Q), DASS-21, PSQI, MoCA, and a computerized cognitive battery measuring inhibition (Go/No-Go), flexibility (Task Switching), and working memory. Results: Post-intervention analyses revealed significant improvements in subjective cognition (SCD-Q, p < 0.001), sleep quality (PSQI, p < 0.001), and emotional distress (DASS-21, p < 0.001). Objective cognitive performance also improved, with significant gains in MoCA scores (p = 0.047) and executive function metrics. Spearman correlation analysis indicated a significant link between cognitive and emotional changes: longitudinal reductions in SCD scores correlated with concurrent reductions in emotional distress (rho = 0.471, p = 0.009). Furthermore, higher baseline SCD scores predicted greater improvement in emotional outcomes (rho = −0.540, p = 0.002). Conclusions: ExoBDNF supplementation significantly enhanced cognitive performance, sleep quality, and emotional well-being. The findings demonstrate that improvements in subjective cognition are closely tied to alleviated emotional distress, supporting the gut–brain axis as a viable therapeutic target for early-stage cognitive decline. Full article

Background: Academic performance among university students is shaped by multiple factors, especially during examinations. This study aimed to explore the relationship between sleep quality, executive attention, and anxiety to identify potential predictors of academic performance across different academic fields. Method: Fifty-one students, between 19 and 25 years (M = 20.04, SD = 1.11), enrolled in the second year in Medicine (27.5%), Law (39.2%), and Economics (33.3%) programs at a university in Lisbon. The sample has mostly full-time students (98.04%), and female (68.6%). Data collection took place during examination periods and included: Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESE), State-Trait Anxiety Inventory (STAI), Beck Depression Inventory-II (BDI-II), Stroop Test and Go/No-Go task. Results: Our findings revealed significant differences across academic fields: medical students reported poorer sleep quality, law students demonstrated reduced executive attention, and economics students exhibited better sleep but weaker inhibitory control. Sleep quality and state anxiety significantly predicted academic performance, whereas executive attention did not. Conclusions: These results underscore the importance of addressing sleep hygiene and anxiety management among university students, regardless of academic discipline. Institutional initiatives, including structured stress-reduction programs and educational support services, may equip students with the tools to manage academic pressures and enhance cognitive functioning and overall psychological well-being. Full article

Executive function is crucial for the physical and mental health as well as social adaptation of preschool children, and cognitively engaging physical activity may serve as an effective intervention. This study employed a pre-post experimental design with a repeated measures ANOVA to examine the intervention effects and underlying mechanisms of a 20 min cognitively engaging physical activity on preschool children’s executive function. A total of 56 preschool children were recruited and randomly assigned to either the cognitively engaging physical activity group or the conventional physical activity group. Executive function was assessed before and after the intervention using Go/No-Go, 1-back, and dimension-changing card classification tasks. Functional near-infrared spectroscopy was employed to monitor changes in oxygenated hemoglobin concentration in the prefrontal cortex during cognitive tasks. Results indicate that acute cognitively engaging physical activity effectively modulates oxygenated hemoglobin concentration in specific regions of the prefrontal cortex in preschool children, leading to an immediate enhancement in working memory capacity. This approach demonstrates potential advantages in inhibitory control, while no significant differences were observed in cognitive flexibility. Furthermore, post-intervention changes in inhibitory control and working memory showed significant positive correlations with changes in prefrontal oxygenated hemoglobin concentration. These findings provide scientific evidence for applying cognitive engagement elements in cognitive development and theoretical support for designing targeted physical activity interventions. Full article

Background: Opioid use disorder (OUD) and associated overdose deaths have reached epidemic proportions worldwide over the past two decades, with death rates for men consistently reported at twice the rate for women. We have recently reported sex-specific differences in electrocortical activity in persons with OUD in a visual object recognition task. The mesolimbic dopamine (DA) system is implicated in OUD but also plays a critical role in some disorders of visual attention and a modulatory role in the processing of visual stimuli in the blue cone pathway of the retina. We hypothesized that electrocortical responses to color stimuli would be affected differentially in men and women with OUD. Methods: Using a controlled, cross-sectional, age-matched (18–56 years) design, we evaluated color processing in male and female subjects recruited from a community-based, high-intensity residential substance abuse and detoxification treatment program. We evaluated electroencephalogram (EEG) event-related potentials (ERPs) and reaction time (RT), in male and female participants with OUD (n = 38) vs. sex- and age-matched non-OUD control participants (n = 37) in a simple color recognition Go/No-Go task, as well as perceptual and behavioral responses in physiological and neuropsychological tests. Results: N200, P300, and late potential (LP) Relevant stimulus-induced ERPs were evoked by the task and were well-differentiated from Irrelevant distractor stimuli. P300 amplitudes were significantly greater and N200 and LP latencies were significantly shorter in male vs. female non-OUD controls in this task. There were significant sex differences in N200, P300, and LP amplitudes and latencies between male vs. female non-OUD subjects and OUD differences with blue color as the Relevant stimulus. In the Binocular Rivalry Test, there were shorter dwell times for perceiving a blue stimulus in male OUD subjects and there were significant sex and OUD differences in neuropsychological tests including Finger Tapping, Trails A/B, and Symbol Digit Modalities Test. Conclusions: These findings suggest that there are significant sex-related physiological, perceptual, and cognitive differences in color processing that may result from deficits in DA production in the retina that mirror deficits in mesolimbic DA transmission correlating with OUD, suggesting that blue color processing has the potential to be an effective biomarker for brain DA and for diagnosis and monitoring of treatment efficacy in substance use disorders. Full article

Background/Objectives: Computational studies using drift diffusion models on go/no-go escape tasks consistently show that individuals with suicidal ideation (SI) preferentially engage in active escape from negative emotional states. This study extends these findings by examining how individuals with SI update beliefs about action–outcome contingencies and uncertainty when trying to escape an aversive state. Methods: Undergraduate students with (n = 58) and without (n = 62) a lifetime history of SI made active (go) or passive (no-go) choices in response to stimuli to escape or avoid an unpleasant state in a laboratory-based negative reinforcement task. A Hierarchical Gaussian Filter (HGF) was used to estimate trial-by-trial trajectories of contingency and volatility beliefs, along with their uncertainties, prediction errors (precision-weighted), and dynamic learning rates, as well as fixed parameters at the person level. Bayesian mixed-effects models were used to examine the relationship between trial number, SI history, trial type, and all two-way interactions on HGF parameters. Results: We did not find an effect of SI history, trial type, or their interactions on perceived volatility of reward contingencies. At the trial level, however, participants with a history of SI developed progressively stronger contingency beliefs while simultaneously perceiving the environment as increasingly stable compared to those without SI experiences. Despite this rigidity, they maintained higher uncertainty during escape trials. Participants with an SI history had higher dynamic learning rates during escape trials compared to those without SI experiences. Conclusions: Individuals with an SI history showed a combination of cognitive inflexibility and hyper-reactivity to prediction errors in escape-related contexts. This combination may help explain difficulties in adapting to changing environments and in regulating responses to stress, both of which are relevant for suicide risk. Full article

This study proposes a component-based model for assessing risks in the design of high-tech products. The model took into account the novelty of components, which affected the risk level in the development process. The risk assessment was based on fuzzy set theory, which allowed determination of the degree of importance of risk-generating factors, such as technical, economic, and organizational risks. The components were divided into “old” ones with the possibility of adaptation and “new” ones being implemented for the first time. The structure of the project included adaptation, acquisition, and development of new components. The component-oriented approach allowed for a reduction in the negative impact of risks in the early stages of development while optimizing decision-making on further product development. A case study involving the development of unmanned aerial vehicles (UAVs) was conducted to demonstrate the model’s applicability. The assessed aggregated project risk varied from 0.0992 for projects based primarily on reusable components to 0.1902 for those involving a high proportion of newly developed components. The model’s sensitivity to component novelty made it possible to differentiate between low- and moderate-risk design scenarios. This is especially valuable for early-stage project selection and risk-informed “go/no-go” decisions in the design of complex systems. Full article

Background/Objectives: The integration of psychological techniques, such as psyching-up, into sports training has been increasingly explored for its potential to enhance athletic performance and cognitive function, especially in young athletes. This study aimed to examine the effects of combining psyching-up techniques with cognitive challenges on psychophysiological responses and visuo-auditory attention in adolescent competitive swimmers. Methods: A total of 48 male competitive swimmers were randomly assigned to three groups: the Psyching-Up and Cognitive Group (PCG), the Cognitive Training Group (CGT), and a Control Group (CG). The intervention involved ten training sessions, where the PCG received psyching-up techniques, while both the PCG and CGT participated in cognitive training tasks. Key assessments included cognitive performance tests (Bells Test, Trail Making Test Parts A and B, Go/No-Go Auditory Task), heart rate (%HR max), blood lactate levels, perceived exertion (RPE), and mood state (Total Mood Disturbance). Results: The PCG showed significant improvements in cognitive performance, with fewer omissions in the Bells Test (p = 0.041) and faster reaction times in the Trail Making Test (Part A, p = 0.002; Part B, p = 0.001). In the Go/No-Go Auditory Task, the PCG exhibited faster reaction times and a higher hit rate (p = 0.001). There were no significant differences in physiological responses, with %HR max and blood lactate levels showing stable trends across groups. However, the PCG reported significantly higher enjoyment (p < 0.001) and a reduction in Total Mood Disturbance (p < 0.001). Conclusions: Integrating psyching-up techniques with cognitive challenges positively impacts cognitive performance and psychological well-being in adolescent swimmers, without altering physiological responses. These findings highlight the potential of psychological interventions to enhance performance and overall athlete experience in youth sports training. Full article

Background/Objectives: An increasing number of children and adolescents with mental health issues across many countries highlights the need for effective, accessible prevention strategies. Within the Research Domain Criteria framework, irritability—an emotional response to expected but blocked rewards—has been identified as an early indicator of declining mental well-being before the onset of mental disorders. Developing reliable yet resource-efficient methods to assess irritability is an important first step toward targeted prevention. Methods: We tested the German Version of a frustration Go/No-Go task enabling to deliberately induce frustration through expected but blocked rewards in N = 68 children aged eight to ten (mean age = 8.9 years, SD = 0.7; 36 females) and parallelly assessed irritability with the 7-item low cost Affective Reactivity Index (ARI) with ratings of parents, teachers and children. Results: The German Version of the frustration Go/No-Go task proved reliable and valid. Teacher ratings demonstrated the highest predictive validity for irritability among all informants. Conclusions: Both the 7-item ARI, rated by teachers, and the frustration Go/No-Go task are recommended for assessing irritability. In the future, irritability assessments should be implemented for all primary school-aged children. Based on the components that contribute to irritability, targeted prevention measures should be offered. Full article

Background/Objectives: Response inhibition, a core aspect of executive function, is commonly evaluated using the Go/NoGo task. While previous research has demonstrated that short-term practice can influence both behavioral and neural markers of response inhibition, the role of task difficulty—particularly when manipulated through short interstimulus intervals (ISIs)—remains underexplored. This study investigated the effects of short-term repeated practice on behavioral performance and neural activity during a high-difficulty Go/NoGo task with a short ISI. Methods: Fifteen healthy young adults completed a visual Go/NoGo task in four repeated sessions within a single day. The task involved a 600 ms ISI, 100 ms stimulus duration, and a 20% NoGo stimulus frequency. Behavioral outcomes included response time (RT) and error rate (ER). Neural activity was recorded via electroencephalography (EEG), focusing on event-related potentials (ERPs) associated with response inhibition, specifically the NoGo-N2 and NoGo-P3 components. Results: No significant changes were observed in RT or ER across sessions, indicating no improvement in behavioral performance. Similarly, NoGo-N2 amplitudes remained stable. However, a significant reduction in NoGo-P3 amplitude at the Fz electrode was found in later sessions, suggesting decreased frontal cortical engagement in response inhibition. Conclusions: Although short-term repeated practice of a high-difficulty Go/NoGo task did not enhance behavioral performance, it was associated with reduced neural activity related to response inhibition. These findings suggest that neurophysiological adaptations may occur even in the absence of observable behavioral changes, particularly under high task demands. Full article