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Underlying biological mechanisms leading to the dramatically increased cardiac mortality in patients with schizophrenia (SCZ) are largely unknown. Cardiac autonomic dysfunction (CADF), which has been extensively described in patients with SCZ, represents an important physiological link to cardiovascular disease (CVD). This study investigated the prevalence of CADF in patients with SCZ using HRV across multiple domains (time and frequency, nonlinear dynamics, complexity measures, symbolic dynamics, and segmented Poincaré plot analysis). HRV-based clustering classified 119 SCZ patients as having or not having CADF based on deviations from 119 age- and sex-matched healthy controls. Our findings showed that approximately half of the patients had normal cardiac autonomic function, while the other half had significant abnormalities. The severity of CADF correlated with age, body mass indes (BMI), disease duration, and symptom severity. About half of SCZ patients have significant CADF, which increases their risk for cardiac events. These findings highlight the potential of HRV-based biomarkers in improving CVD risk prediction and stratification in SCZ. Future research should explore integrating HRV analysis with other biomarkers to enhance early detection and intervention strategies., Competing Interests: Competing interests: The authors declare no competing interests., (© 2025. The Author(s).)

The detection and quantification of coupling strength and direction are important aspects for achieving a deeper understanding of physiological regulatory processes in the field of network physiology. Due to the limitations of established approaches, we developed directionality indices based on simple mathematical symbolization principles and simple computational procedures that allow a quick and comprehensive understanding of the underlying couplings. We introduced a new directionality index ( D HRJSD ) derived from the pattern family density matrix of the High-Resolution Joint Symbolic Dynamics (HRJSD) approach and its multivariate version (mHRJSD) to determine coupling direction and driver-response relationships. The mHRJSD approach contains the multivariate directionality index D mHRJSD ( D mHRJSD ( x , y | z ), D mHRJSD ( x , z | y ), and D mHRJSD ( y , z | x )), allowing us to determine the primary driver **D mHRJSD , the secondary driver *D mHRJSD, and the dominant responder - D mHRJSD in multivariate systems that are at least weakly coupled. Different linear and non-linear bi- and multivariate coupled systems (Gaussian autoregressive models) with different mutual influences were generated to validate these indices. The simulation results showed that D HRJSD was able to correctly detect the dominant coupling direction in linear bivariate coupled systems but was partly able to detect the dominant coupling direction in non-linear bivariate coupled systems. The proposed directionality index D mHRJSD derived from the mHRJSD approach is able to correctly detect the driver-responder relationships in linear coupled systems. The main advantages of the newly introduced directionality indices include their insensitivity to non-stationary time series, their ability to capture couplings through a simple, fast, and easy-to-implement symbolization procedure, and their scale invariance. Additionally, they are independent of time series length, model order selection, and the procedure for determining their significance level., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2025 Schulz, Schumann, Bär, Haueisen, Seifert and Voss.)

Body image is a core identity facet in anorexia nervosa (AN). Current literature outlines body image as a multidimensional construct, characterized by perceptual, cognitive, and emotional components, which explain how individuals perceive, think, and behave in relation to their body. The purpose of this scoping review is to uncover neuropsychological disturbances in AN related to body image by focusing on its different behavioral and neuronal assessments, aiming to provide a broad overview of common findings and limitations. Additionally, we explore the role of somato-sensory/somato-motor components and physiological markers underlying body image disturbances, which have not been extensively examined in previous studies. Literature screening was performed across three databases (PubMed, PsycINFO, Scopus). We classified behavioral, physiological, and neuroimaging studies according to their degree of involvement with body image dimensions and discussed the primary findings for each component. A total of 4015 studies were identified, of which 107 were eligible (84 behavioral and 23 neuroimaging studies) based on eligibility criteria, covering research from 1973 to 2024. Notably, of those which specified the following factors: 16 studies focused on the restrictive subtype (AN-r), two on the binge-eating/purging subtype (AN-b/p), and 19 examined both AN-r and AN-b/p; finally four on the atypical subtype; 11 on the weight-recovered state (WR) and three included also male participants. The mean age across all studies was 20.1 years (SD = 3.79). Our findings reveal that body image disturbances in AN are not limited to the overestimation of body size but also encompass cognitive, emotional, and somato-sensory aspects. A strong drive for thinness emerged as a prominent cognitive factor in maintaining the disturbance, along with altered autobiographical recall, executive function, and attentional biases toward body-related stimuli. Emotional regulation difficulties, altered interoceptive awareness, and distorted somato-sensory aspects-reflected in tactile and motor processes-were highlighted. In addition, increased autonomic reactivity to body image stimuli, indicating a sympathetic/parasympathetic imbalance, is supported by specific cortical-subcortical functional alterations. Our review emphasizes that body image distortion in AN should not be viewed merely as a perceptual deficit but rather as a complex cognitive-emotional and somato-sensory process., Competing Interests: Declarations. Ethics approval and consent to participate: Not applicable. Competing interests: No support was received for the work. The authors declared that they do not have conflicts of interest., (© 2025. The Author(s).)

Objective . Heart rate variability (HRV) is an important indicator of cardiac autonomic function. Given its clinical significance, reliable HRV assessment is crucial. Here, we assessed test-retest stability, as a key aspect of reliability, quantifying the consistency of a measure when repeated under the same conditions. Approach . This observational study includes healthy individuals. A 20 min electrocardiogram was recorded at rest in a supine position and during deep breathing in two lab sessions within one week, at the same time of day. HRV indices from time domain, frequency domain, nonlinear dynamics, and information-theoretic complexity were assessed using a validated toolbox. Additionally, heart rate variations per respiratory cycle were evaluated during deep breathing. Lifestyle factors such as perceived stress, mood, physical activity, sleep quality were assessed prior to both sessions. Intra-class correlation (ICC) and coefficients of variation (CVs) were used to assess the concordance between the two measurements and the relative deviation, respectively. Main results . From 62 screened individuals, 51 participants were recruited from the local community. One participant opted out for personal reasons, and another with frequent premature beats was excluded, leaving a final sample of 49 individuals. Most self-rated psychological and lifestyle indicators showed substantial agreement, though participants reported less stress and better mood in the second session. At rest, ICC of HRV ranged from 0.50 to 0.83, with CV from 5% to 41%. Spectral HRV measures were less reliable than time domain parameters. Nonlinear and time domain features had substantial to nearly perfect agreement. Complexity measures had low CVs but limited test-retest correlation. The stability indices of HRV during deep breathing were not significantly different from those during rest. Test-retest differences in root mean square of the successive beat-to-beat interval difference were not sufficiently explained by lifestyle factors. Significance. Test-retest stability of HRV depends considerably on chosen measures. Our data suggest that HRV can be assessed reliably using time-domain indices at rest., (Creative Commons Attribution license.)

Heart rate variability (HRV) is a key indicator of cardiac autonomic function, making reliable assessment crucial. To examine the test-retest stability of resting HRV in healthy individuals, fifty participants attended two lab sessions within a week, at the same time of day. After a 5-minute acclimatization period, electrocardiogram and respiration were recorded at rest. For validation, average heart rate and RMSSD were assessed over 15 minutes using a validated open-source toolbox. Test-retest agreement was evaluated using intra-class correlation (ICC), and coefficients of variation (CV). Mean heart rate showed high stability (ICC = 0.81, CV = 6%), while RMSSD had lower concordance (ICC = 0.75) and greater variation (CV = 30%). These findings indicate good test-retest agreement for standard HRV features. However, a wide range of methodologies exists for assessing various properties of heart rate dynamics. This database is intended to support other researchers in testing additional HRV metrics to evaluate their reliability in healthy individuals., Competing Interests: Competing interests: All contributors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2025. The Author(s).)