Biology and Life Sciences

Abstract: Power-law efficient coding is widely used to explain how perception allocates limited resources. In many studies, the power-law exponent q—the exponent on the prior density, such that J(x)∝p_prior(x)^q—is treated as the central result: a larger q is read as a stronger tilt toward likely stimuli, and a change in q is interpreted as a change in what the system optimizes—for example, from accuracy to reward. We show that this interpretation is not licensed by the model itself. The model has three theoretical parameters—a coding objective α , a resource-constraint form β, and a budget c—but produces only two observable quantities: the exponent q and the scale k. Because q=1/(α+β) , the same fitted code corresponds to a one-dimensional family of theoretical interpretations. We call this family a gauge orbit; a simpler name is a family of equivalent interpretations. Along this family, the code and all behavioral predictions remain fixed, while α and c change. Therefore q alone cannot identify what a system optimizes. This redundancy is not merely a caution. It yields three practical tools. A prior-free closure test, c=k^1/q , checks any infomax claim without estimating the stimulus distribution. An independently measured budget reduces the orbit to at most two candidate interpretations, with the residual ambiguity physiological rather than behavioral. And an observed budget below the orbit minimum or at or above the stimulus support measure falsifies the framework at the fitted (q,k) . We illustrate these tools by re-analyzing a reward-manipulation study and show that a null result on k cannot be read as a null result on the budget, because k is dimensionally incommensurable across a change in q. The broader lesson is not that the framework is flawed, but that its central exponent carries less theoretical information than its reporting practice assumes. A model can over-determine its observable predictions relative to its theoretical parameters, and when it does, the excess has an exact structure—one that can be written down, tested, and in part broken. Recognizing that structure is what makes q interpretable rather than merely reportable.

Abstract: Prevention trials promise to prevent an event, such as a first depressive episode, a first psychotic episode or the first use of a drug, but most count a diagnosis that requires that event, and many enrol people who have already had it. In surveys of ClinicalTrials.gov, 31 of 38 randomized trials framed as preventing the onset or incidence of depression (82%, 95% CI 67–91) admitted people who had already had a depressive episode, and 68 of the 72 trials across all framings that did so registered a single estimate for first and recurrent episodes. Seventeen of 20 trials of transition to psychosis (85%, 64–95) admitted people who had already had brief psychotic episodes, and only one registered psychotic episodes regardless of duration. A meta-analysis of depression onset pooled a trial in which 80% of participants had had a previous episode, recording the share as 55%. The problem is structural: diagnostic risk is the product of the risk of the gate event and the probability of completing the remaining criteria, so fewer diagnoses cannot, at any sample size, show that the event was prevented. In a randomized zoster-vaccine stratum, the nested endpoint fell by 67% while the event it requires fell by 37%. A four-question gate audit, three of whose questions are answered from the protocol before randomization, detects the mismatch and states what each trial can claim. It applies wherever a diagnosis requires a prior event and can be built into trial registration, protocol review, reporting and synthesis.

Abstract: It is now known that when autistic spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD) occur together the comorbid condition is more difficult to manage than either alone. In females masking and diagnostic overshadowing of both conditions, combined with the fact that ADHD in females appears to be largely inattentive, makes the combined condition more challenging for the clinician and the subject alike. It is only known by an acronym, AuDHD, is not yet a formally recognised mental health condition, and the aforementioned recognition problems make its true prevalence unknown. This also leads to an underestimate of how commonly ASD occurs in the female ADHD population and these unknowns lead to significant management problems. The indirect but potentially accurate way to find the unknowns is by Bayes’ theorem, and the independent variables used to find the unknown dependent variables were established from the author’s 2014-2022 clinical cohort of 794 autistic females under the age of 18, combined with published data. Due to the extensive masking and overshadowing of the prevalence of ASD in both the overall population and the ADHD population, the true prevalence of AuDHD appears to be about 25 times the reported prevalence. The effectiveness of ADHD medications in AuDHD was measured as were the relative proportion of internalising and externalising behaviours. The implications of these results for management are discussed. In assessing the degree of overshadowing, a value for overshadowing in males with ASD has been derived for the first time.

Abstract: Background. Animals meet the same sensory classes under different physiological and social conditions and select different actions. How experience changes the mapping from stimulus to behavioral program, without adding any act to the motor repertoire, is a central question for mechanistic neuroendocrinology. Proposal. We separate three operations. Open denotes the physiological state in which a neural substrate is writable; write denotes durable, activity-dependent modification of that substrate; and read denotes recovery of the modified architecture into a competition among behavioral programs for common effectors. We propose that local inhibitory configuration, comprising GABAa receptor subunit composition and neurosteroid tone, contributes to that competition by determining how a broadly distributed permissive signal is transformed at each node. Evidence and predictions. Prairie voles (Microtus ochrogaster) supply a tractable mammalian case, since reproductive maturation, pair bonding, selective aggression, parental care and partner loss repeatedly remap social stimuli onto different outputs, each with an accessible neuroendocrine handle. The critical mechanistic requirement is non-proportional receiver function: when all channels respond proportionally to a common field, that field alters overall gain while leaving unchanged which program wins. Conclusions. The framework yields discriminating physiological tests linking life-history transitions, local receiver properties and behavioral selection, and it remains agnostic about whether any single molecular signal is universal across taxa.

Abstract: Background/Objectives. Fatigue is defined as an overwhelming sense of tiredness, weakness, or ex-haustion, which can be physical, psychological, or a combination of both. Evidence suggests that fa-tigue is more prevalent among patients with inflammatory bowel disease (IBD) than in the general population. The aim of this study was to assess the prevalence of fatigue among Swedish IBD pa-tients. Another aim was to increase knowledge about factors that may contribute to fatigue, and strat-egies for managing fatigue. Methods. Swedish IBD patients were asked to complete the IBD Fatigue Scale. Analyses involved both a quantitative and a qualitative approach. Results. A total of 675 pa-tients participated in the study. Patients with active disease, continuous symptoms, extraintestinal manifestations, and impaired wellbeing had higher scores of fatigue. Four categories relating to fa-tigue were identified: (1) fatigue difficult to define and attribute, (2) fatigue arising from interacting bodily and psychosocial burdens, (3) managing a limited and fluctuating supply of energy, and (4) restoring energy through activity, support and recovery. Participants frequently described fatigue as arising from an interaction between disease activity, comorbid conditions, psychological distress, sleep problems, pain, and everyday life demands. Conclusions. Although fatigue was more severe among participants with active disease, continuous symptoms and impaired wellbeing, the free-text responses demonstrated that patients frequently perceived comorbidities, disturbed sleep, pain, psy-chological distress and demanding life circumstances as additional contributors. Management in-volved balancing rest and activity, planning limited energy, and drawing on supportive relationships and restorative environments. These findings support a holistic and person-centred approach in which fatigue is assessed beyond intestinal disease activity.

Abstract: Prey companion species — rabbits, guinea pigs, chinchillas, and small rodents — are clinically recognized for concealing overt signs of pain, a behavior long attributed loosely to "prey instinct." This review proposes an integrated neuroanatomical-evolutionary framework explaining why and how this masking occurs. We synthesize evidence on the periaqueductal gray (PAG) and rostral ventromedial medulla (RVM), the core descending pain-modulation circuit, and link its function to stress-induced analgesia (SIA), a conserved antipredator adaptation that suppresses nociceptive output during acute threat exposure. We argue that pain masking is not a passive absence of expression but an active, centrally mediated suppression mechanism with clear survival value: an animal displaying pain is a visible target for predators. We map documented behavioral pain indicators (grimace scales, postural changes, activity suppression) onto this circuit-level mechanism and discuss the direct clinical consequence — systematic underestimation of pain severity — with implications for analgesic protocol design in exotic companion medicine. We conclude with testable predictions, such as context-dependent grimace-scale variability under simulated predator cues, that could validate the framework experimentally. This synthesis aims to shift the clinical narrative from "hard to read" prey species toward a mechanistically grounded model that can inform pain-assessment tools and analgesic dosing philosophy in rabbits, rodents, and other small exotic mammals.

Abstract: Predation risk is often communicated socially, allowing animals to use a combination of behavioral and chemical cues to assess environmental threats. Zebrafish, a highly social aquatic species, have been shown to exhibit anti-predation behaviors under exposure to the chemical cue hypoxanthine-3N-oxide (H3NO). While concentration-dependent anti-predation responses have been studied, it remains unclear how subjects behave when only visually exposed to shoals alarmed by different concentrations of H3NO. The present study examines whether zebrafish modify their social preference and anxiety-like responding while observing conspecifics exposed to varying H3NO concentrations. Adult male and female zebrafish performed a 3-chamber open-tank free-swim task with visual access to an unlarmed shoal on one side and a shoal exposed to 1.5 nM, 3 nM, or 5 nM H3NO on the other side. Male and female zebrafish exhibit similar behaviors and preference for the unalarmed shoals when exposed to 1.5 nM and 3 nM alarmed shoals. Interestingly, sex differences emerge when subjects are visually exposed to a shoal receiving 5 nM H3NO. At this concentration, males exhibit closer proximity to the alarmed shoal and greater locomotor activity compared to females, whereas females maintain their preference for the unalarmed shoal. These findings indicate that zebrafish can visually extract graded information about predation threat from conspecifics' alarm behavior and modify responding in a sexually dimorphic manner.

Abstract: Traditional accounts of cognitive evolution often treat learning and instinct as zero-sum substitutes, in which increased behavioural plasticity necessarily displaces hard-wired routines. We challenge this view using a formal model of behavioural hypercycles: functionally integrated assemblies of behavioural components whose joint performance contributes to adaptive outcomes and promotes the persistence of the behavioural system itself. The model predicts that genetic assimilation proceeds selectively rather than uniformly. Rather than assimilating entire behaviours at once, evolution acts more like a greedy algorithm, preferentially canalizing behavioural bottlenecks that are difficult, costly, or reliability-limiting. Extending the model to multiple tasks reveals that behavioural reuse amplifies this process, causing recurrent behavioural primitives to experience disproportionately strong selection for canalization. Assimilation pressure therefore accumulates across the behavioural repertoires in which a component participates, favouring the stabilization of widely reused behavioural building blocks. Finally, allowing learning investment to evolve shows that learning and instinct remain local substitutes within fixed behavioural repertoires, but can become globally complementary when learning expands opportunities for behavioural reuse across tasks. Learning thereby acts as an engine of discovery, exposing reusable behavioural components to selection, while genetic assimilation progressively stabilizes them. The framework generates a range of testable predictions and provides a novel account of how sophisticated learning capacities may promote, rather than displace, the evolution of instinct.

Abstract: Background: Anorexia nervosa (AN) is a severe psycho-metabolic disorder characterized by persistent energy restriction and substantial loss of adipose tissue. Despite profound undernutrition and measurable immune alterations, individuals with acute AN (AN-acute) have been reported to experience fewer clinically evident infections than expected from conventional models of malnutrition. This creates an apparent immune paradox. Scope of Review: Immune findings in AN are heterogeneous, reflecting differences in illness duration, eating-disorder subtype, nutritional severity, and methodology. Furthermore, persistent physical activity, a prominent feature of AN-acute, has received relatively little attention despite its important immunomodulatory effects in healthy individuals. This review presents a hypothesis integrating concepts from exercise physiology and immunometabolism with findings on immune function in AN-acute. Hypothesis: The immune phenotype of AN-acute may reflect selective allocation of limited energy, consistent with immunometabolic principles. It is proposed that severe energy restriction may permit sufficient neutrophil- and macrophage-mediated innate defense to contain pathogens early while constraining the more metabolically demanding activation and expansion of adaptive immunity. Simultaneously, systemic inflammation may remain restrained through multiple metabolic and endocrine mechanisms, potentially reinforced by repeated contraction-derived myokine IL-6 signaling associated with persistent hyperactivity. Conclusion: This model proposes that preserved innate containment, constrained adaptive escalation, and restrained systemic inflammation interact in AN-acute to reduce the clinical expression of infection. It offers a testable framework linking starvation, hyperactivity, immunometabolism, and immune function.

Abstract: Background/Objectives. Neurofibromatosis type 1 (NF1) is associated with neurocognitive difficulties and a high prevalence of sleep problems. However, the relationship between sleep and cognitive functioning in youth with NF1 remains poorly understood. This study examined associations between sleep characteristics and cognitive functioning in children with NF1. Methods. Thirty-five children with NF1 (6-16 years) completed a comprehensive neuropsychological evaluation assessing attention, executive functioning, memory, and academic achievement. Parents completed measures of sleep, attention, and executive functioning. Primary sleep variables included PROMIS Sleep Disturbance, PROMIS Sleep-Related Impairment, and sleep duration. Correlational analyses, group comparisons, and exploratory hierarchical regressions were conducted. Results. Forty percent of participants met criteria for clinically elevated sleep disturbance and sleep-related impairment. Greater sleep disturbance and sleep-related impairment were associated with higher levels of parent-reported attention and executive functioning difficulties. Sleep disturbance was also associated with poorer verbal memory. Children with clinically elevated sleep-related impairment demonstrated significantly greater attention and executive functioning difficulties than those without impairment. In exploratory regression analyses, sleep variables accounted for significant incremental variance in attention problems (ΔR² = .29), overall executive functioning (ΔR² = .31), working memory (ΔR² = .37), and performance-based memory outcomes (ΔR² = .32) beyond demographic and ADHD-related factors. Conclusions. Sleep difficulties are common in children with NF1 and are associated with variability in attention, executive functioning, and memory. Sleep may represent a clinically meaningful and potentially modifiable contributor to neurocognitive outcomes in NF1, warranting routine assessment and further investigation as a therapeutic target.

Abstract: Anthropogenic prehistory may be divided into two subsequent phases, the first one from the Last Common Ancestor (LCA) between humans and great apes till the emergence of the genus Homo, and the second phase onwards from then. Until hominins appeared, LCA had lived predominantly on trees, while Homo finally lived only on the ground. After LCA and before Homo, the intermediate bimodal transition period from 7 to 2 Myr BP was coined by the emergence of systematic bipedal gait, breaking the previously uniform quadrupedal locomotion symmetry. By contrast to versions of the common savannah hypothesis, this paper suggests an alternative fictitious scenario of periodic migration between alternatingly inhabitable arboreal refuges. Possibly caused by regional climate change, yet tree-climbing hominins were additionally forced to genetically develop speedy and efficient bipedal locomotion for survival during their temporary but extended regular excursions across open territory. Increasingly upright locomotion resulted in offspring’s early weaning, and in turn in the emergence of childhood with enhanced lethal risks for toddlers. Related selective pressure caused transformations of reproductive traits from gradual sexual selection in apes to undulating sexual conflicts in hominins. Between LCA and Homo, consistent with fossil evidence, the evolutionary bimodal transition phase, with forelimbs for climbing and hind limbs for running, did not necessarily require enlarged brains for advanced mental capabilities, nor specific communication or new forms of social cooperation such as those successively found in Homo. After emigration from arboreal habitats, allotted food access caused previous promiscuous mating being replaced by sexual pair bonding with exclusive paternity of Homo. Assumingly, broken spatial and temporal environmental symmetry had induced related symmetry breaking of hominin behaviour, their anatomic structures and reproduction habits, with consequences lasting to the present day.

Abstract: Nonsuicidal self-injury (NSSI) is often described through functional labels such as emotion regulation, self-punishment, interpersonal influence, or escape from aversive internal states. These labels describe important functions but do not explain how self-injury becomes selected under stress. This paper proposes the Inward-Routed Mobilization Model (IRM) of NSSI, a mechanism-level account of selection under high activation, reduced deployable capacity, and constrained outward representation. IRM proposes that NSSI becomes more likely when mobilization rises, negative affect cannot be safely represented toward an over-idealized figure, outward expression is appraised as relationally or psychologically dangerous, and the body becomes the most immediate site for state change. The relevant mobilization may appear as protest, hurt, disappointment, shame, humiliation, or boundary-relevant action pressure without being consciously labeled as anger. The model specifies a common origin pathway: over-idealized figure constraint, truncated negative affective mobilization, inward routing, and bodily state transition. IRM yields testable predictions for ecological momentary assessment, developmental research, clinical formulation, and treatment studies focused on constraint repair, capacity restoration, and safe outward throughput.

Abstract: A central feature of episodic memory is the ability to transform similar and overlapping experiences into distinct representations, a process known as pattern separation. This function is critically linked to the hippocampus, particularly the dentate gyrus (DG) and its projections to CA3. Here, we introduce the Visual Sensory Memory Task (VSMT) as a novel paradigm for assessing mnemonic similarity processes in healthy adults. The VSMT uses asemantic visual stimuli derived from abstract pink-noise images and allows controlled manipulation of stimulus similarity while minimizing learning effects. Behavioral results showed reliable discrimination between targets and foils, whereas low-similarity lures were more difficult to identify than high-similarity lures, providing initial evidence for sensitivity to mnemonic similarity. Using 3T fMRI, we measured BOLD responses during encoding of asemantic stimuli. Robust bilateral hippocampal activation was observed across all stimulus categories. Exploratory atlas-guided localization suggested distributed activation for foils, whereas activation peaks for targets and high-similarity lures were spatially localized to regions encompassing CA1 and CA4/DG, respectively. These localizations should not be interpreted as evidence of subfield-specific activation given the spatial resolution of the functional data. Consistent with previous studies using explicit memory paradigms such as the Mnemonic Similarity Task, the VSMT differences in hippocampal BOLD response magnitude associated with mnemonic similarity processing. These univariate activation differences are compatible with predictions derived from pattern separation accounts but do not directly demonstrate representational pattern separation. Together, these findings provide initial evidence for the feasibility and potential utility of the VSMT for investigating hippocampal mechanisms related to mnemonic similarity and pattern separation.

Abstract: For 10 months, our team tested the communication and cooperation skills, as well as theory of mind, of three adult male western lowland gorillas at the Opole Zoo in Poland. The cognitive tasks presented to the gorillas enriched their daily routine and interactions with their keepers. The aim of this article is to analyze whether the cognitive tasks presented to the gorillas correlated with behavioral changes toward more frequent communication and cooperation with their caretaker, as well as toward positive emotional responses, compared to their state before performing the tasks. We used behavioral observation protocols, focused on observing and interpreting changes in the gorillas’ behavior while they performed the cognitive tasks. The results of the study indicate that two out of three individuals showed an increase in communicative and cooperative interactions with their caretaker, as well as greater affective stability, which may be an indicator of a stronger bond rooted in positive emotional experiences. As a result, appropriately selected cognitive tasks can provide sensory and social enrichment, which corresponds to the fourth and fifth domains of David Mellor’s welfare model, relating to communicative and affiliative behaviors, as well as the quality of animals’ affective and mental experiences in zoos.

Abstract: This is a stand-alone theoretical article. It is not a protocol, a research proposal, or supplementary material to another manuscript. Conventional psychotherapeutic treatments often face limitations in cases of chronic suffering that persists despite the client's verbal understanding and reflective insight. In this article, I present Implicit Reintegration Therapy (TRI) as a brief, focal approach grounded in affective neuroscience, predictive processing, and nondeclarative memory. The central thesis holds that psychological suffering that does not stem from direct material deprivation is organized as affective shear between adaptive processes oriented toward individual survival and the preservation of social bonds. By conceiving of the body as the primary stage of this tension and of representational systems as matrices of automated response patterns, the model intervenes directly on somatosensory responses active in the present, dispensing with the retrospective reconstruction of childhood. The intervention uses mediated interoceptive confrontation and relational triangulation to promote desensitization of the aversive response and enable reeducation in everyday life. The model is formalized in three clinical hypotheses with explicit criteria for empirical refutation, which establishes the basis for controlled, independent investigation. The article closes with a prospective research agenda, which describes designs that other groups could adopt and does not constitute a study protocol.

Abstract: The objective of this study was to examine the effect of lack of visual input on the ontogeny of fear response. We used a genetically blind chicken model (rc chickens) and used Tonic Immobility (TI) for testing the fear response. There were four blind groups and four sighted groups of rc chickens in this study, and each group had 45 chickens. We perform the TI test at the age of Day 2 and at Days14, 28, and 70, respectively to study the ontogeny of fear response. Blind chickens were more difficult to induce a TI response and stayed in TI for a significantly shorter time compared to sighted controls. The results from the TI tests indicated that the blind males had a slower rate in developing a TI response (from Day 2 to Day 70) than blind females. The blindness of the rc chicken was caused by a deletion in the GC1 locus resulting in the disruption of cGMP metabolism. Besides causing the degeneration of rods and cones in the retina, cGMP deficiency may have direct effect on the brain cells to supress tonic immobility. cGMP also seems to affect male sexual maturity differently than female sexual maturity. Our results indicated that the ontogeny of fear response was dependent on the interaction of age, sex, experience and visual input, and the ontogeny of TI response in rc chickens may not be just reflecting the ontogeny of fear response but also physiological processes affected by the mutation.

Abstract: In natural, continuous sport settings, it remains unclear how athletes use an existing motor schema to parameterize an already learned skill for a new target and how subsequent actions are organized once outcome information becomes available. This study examined initial parameterization after landing-location change and prior-outcome associations with the immediately subsequent serve during continuous table-tennis serving. Twelve male athletes completed the serving task together with task-switching, stop-change, and N-back tasks. Three-dimensional movements were recorded using VICON motion capture, and trial-level generalized estimating equations modeled binary hit outcome and seven kinematic deviations from individualized stable-serving templates. In Stage 1, hit probability was lower under Target change than Target maintenance. Temporal-phasing deviation showed a stronger negative association with hit probability under Target change, suggesting that relative timing was particularly relevant to initial parameterization. Longer training duration was associated with smaller temporal-phasing deviation, while the association between change-trial accuracy and hit probability varied by target context. In Stage 2, a successful t₀ outcome was associated with a higher probability of a t₁ hit. Although t₀ outcome was not consistently associated with t₁ kinematic deviations themselves, the associations of t₁ temporal-phasing and elbow-velocity deviations with hit probability differed according to the preceding outcome. Training duration and change-trial accuracy were also associated with smaller t₁ temporal-phasing and elbow-velocity deviations, respectively. Overall, the findings support initial schema-based parameterization after landing-location change and provide partial observational evidence for prior-outcome associations with next-trial organization.

Abstract: Urbanization drastically alters bird communities, creating an urgent need for practical in-dicators to monitor species colonization and decline. We investigated whether avian boldness, measured by Alert Distance (AD), Flight Initiation Distance (FID), and escape tactics such as escape mode and site, is better related to urban colonization history and ecological opportunities than morphological variables such as body mass. In the high-altitude Neotropical city of La Paz, Bolivia, we assessed five pigeon species in 15 ur-ban green spaces, quantifying abundance and escape behaviors and relating them to sev-eral environmental metrics. The invasive Rock Pigeon exhibited the greatest abundance and boldness, escaping primarily by walking to the ground and preferring impermeable areas. The Eared Dove showed intermediate abundance and boldness but a wider habitat uses than the Rock Pigeon. The recently urbanized Spot-winged Pigeon showed the lowest abundance and boldness, predominantly escaping by flying to elevated perches, demon-strating a strong dependence on tree cover. The Bare-faced Ground Dove was only present in one green area, indicating a process of disappearance in the city, and the Picui Ground Dove was totally absent from our counts, probably due to physiological limitations. Gen-eralized linear models confirmed that body mass did not explain AD or FID, rather, bold-ness was more related to the timing and ecological opportunities for urban colonization in relation to environmental factors. Combining behavioral metrics (AD, FID and escape mode) with population censuses offers a low-cost, highly sensitive tool for monitoring urban wildlife dynamics and guiding biodiversity-friendly urban planning.

Abstract: Valproic acid (VPA) is a widely used anticonvulsant and mood stabilizer and a known teratogen associated with neural tube defects and neurodevelopmental disorders, including autism spectrum disorder (ASD). Prenatal VPA exposure is widely used to model ASD-like behaviors in rodents; however, most studies employ a single dose, and direct comparisons between commonly used regimens are lacking. We therefore compared two widely used VPA doses (300 and 600 mg/kg) administered to pregnant mice on embryonic day 12.5 (E12.5). Male and female offspring were evaluated longitudinally for early neurological development, ultrasonic vocalizations, locomotor activity, anxiety-like behavior, sociability, and working memory. Prenatal VPA exposure produced non-linear, dose- and sex-dependent effects. Early neurodevelopment was largely preserved, with only mild and transient delays that were most evident after 300 mg/kg. In contrast, later behavioral alterations differed according to dose, sex, age, and behavioral measure. Sociability deficits were stable across doses in males but became more pronounced with age in females, whereas working memory impairment predominated after 600 mg/kg during adolescence and after 300 mg/kg in adulthood. These findings demonstrate that increasing prenatal VPA dose does not simply increase behavioral severity but produces distinct neurodevelopmental trajectories that depend on dose, sex, and developmental stage.

Abstract: Cardiac autonomic recovery after exercise is conventionally summarized as a single nocturnal heart rate variability (HRV) average, treating sleep as a passive backdrop rather than an active determinant of recovery. A fragmented but convergent literature indicates instead that autonomic state tracks sleep stage in real time, with parasympathetic dominance concentrated in slow-wave sleep (SWS) and attenuated during REM sleep, and that this coupling is causally, not merely correlationally, linked to post-exercise recovery: enhancing slow-wave activity increases parasympathetic HRV, sleep restriction disrupts nocturnal autonomic state directly, and post-exercise vagal reactivation is depressed on nights following intense exercise, localized to the SWS stage. This review synthesizes the literature into a systems physiology framework in which SWS functions as a determinant of post-exercise cardiac autonomic recovery, integrating brainstem circuitry and neurotransmitter systems, causal manipulations of SWS (acoustic, pharmacological, deprivation-based), exercise dose-response, and boundary conditions (age, sex, training status, sleep, and cardiovascular disorders) under which the coupling is preserved, attenuated, or absent. The resulting effect is graded and window-specific rather than uniform: robust in the early postexercise reactivation phase and during nocturnal SWS, but not established across the full multi-hour recovery curve. The framework is translated into falsifiable predictions and candidate study designs, including critical appraisal of wearable and nearable sleep-tracking validity. Two evidentiary gaps are addressed transparently: the human circuit-level mechanism remains largely inferred from rodent studies, and independent citation-network verification is not feasible for all sources. These findings reposition slow-wave sleep as an integral, mechanistically tractable component of systemic autonomic and cardiovascular physiology rather than as a variable external to it.