In recent years, dementia, mild cognitive impairment (MCI), and behavioral and psychological symptoms of dementia (BPSD) among the elderly have become increasingly important issues [1]. The benefits of daily physical activity in promoting healthy aging are well recognized, and the supporting epidemiological evidence is compelling [2]. Furthermore, understanding the underlying mechanisms is equally important. Recent advances in neuroscience research suggest that the clinical utility of exercise extends beyond mere improvements in muscle strength or cardiopulmonary function. Rather, physical activity appears to modulate an integrated "brain-heart axis (BHA)”, which links central nervous system (CNS) networks with autonomic cardiovascular regulation. Then, it will exert beneficial effects on cognition, emotion, and behavior [3] (Figure 1).

Figure 1: Interrelationship between brain and heart in BHA.

The autonomic nervous system (ANS) serves as a bidirectional communication pathway between the brain and peripheral organs. Through sympathetic and parasympathetic pathways, the ANS continuously regulates cardiovascular function while simultaneously reflecting emotional and cognitive states [4]. Heart rate variability (HRV), a non-invasive measure of beat-to-beat cardiac rhythm fluctuations, has therefore become an accepted biomarker of autonomic regulation and neurocardiac integration. Among HRV indices, high-frequency (HF) power primarily reflects vagal activity. In contrast, low-frequency (LF) power and the LF/HF ratio provide information regarding sympathovagal modulation, although their interpretation remains complex [5]. More recently, nonlinear HRV indices, including Poincare plot parameters (SD1 and SD2), have been recognized as indicators of autonomic adaptability and physiological complexity [6]. These multidimensional measures collectively describe the flexibility of the ANS, which gradually declines during aging and neurodegenerative disorders [7].

The concept of the BHA proposes that HRV represents more than cardiovascular regulation alone. According to the neurovisceral integration model, cardiac autonomic activity reflects the functional integrity of a distributed neural network [8] (Figure 2).

Figure 2: Simplified depiction of the neurovisceral integration model (Revised from Thayer 9).

It comprises the medial prefrontal cortex, anterior cingulate cortex, insular cortex, amygdala, hypothalamus, and brainstem autonomic nuclei [9] (Figure 3). Both figures are revised from the previous reports [8,9]. These interconnected regions coordinate emotional regulation, attention, executive function, stress responses, and autonomic homeostasis. Consequently, reduced HRV has been associated with impaired cognitive performance, depression, anxiety, chronic stress, and dementia. Decrease of vagal function and HRV were observed for the association with increase of glucose, hemoglobin A1c values, overnight urinary cortisol, acute-phase proteins and proinflammatory cytokines [9].

Figure 3: Brain regions relevant to the neurovisceral integration model (Revised from Nikolin 8).

Physical activity influences this neurocardiac network through multiple biological mechanisms. Aerobic exercise enhances vagal tone, suppresses excessive sympathetic activation, improves endothelial function, increases cerebral perfusion, and reduces systemic inflammation. Simultaneously, exercise promotes the release of brain-derived neurotrophic factor (BDNF) [10], insulin-like growth factor-1 (IGF-1), vascular endothelial growth factor (VEGF), and other neuroprotective molecules that facilitate neurogenesis and synaptic plasticity. These adaptations collectively improve communication between cortical and autonomic regulatory centers.

Functional neuroimaging studies provide additional evidence supporting this concept. Regular physical activity has been associated with increased hippocampal volume, improved prefrontal cortical function, and preservation of large-scale resting-state brain networks. Among these, the default mode network (DMN) has attracted particular attention because of its critical role in episodic memory, self-referential processing, and cognitive integration. Alzheimer's disease is characterized by early disruption of DMN connectivity, particularly involving the posterior cingulate cortex, precuneus, medial prefrontal cortex, and hippocampal regions [11]. Exercise interventions have been shown to attenuate age-related declines in DMN connectivity while improving cognitive performance. It suggests that preservation of intrinsic brain networks may represent one mechanism by which physical activity delays cognitive decline.

Electroencephalography (EEG) provides another complementary perspective. Healthy aging associated with adequate relaxation are generally accompanied by increased alpha oscillations, whereas dementia often demonstrates slowing of background rhythms with increased theta and delta activity [12]. Several intervention studies have reported enhanced alpha activity and improved alpha/theta balance following some exercises. They include regular aerobic exercise, mindfulness practice, dance therapy, and music-based interventions [13]. These electrophysiological changes correlate with improvements in attention, mood, and executive function.

Particularly intriguing would be the growing evidence supporting rhythm-based movement [14]. Human locomotion is inherently rhythmic, and synchronized movement to external auditory cues engages widespread neural circuits involving the auditory cortex, cerebellum, basal ganglia, supplementary motor area, and limbic system. Music can provide an external temporal framework that facilitates motor coordination while simultaneously activating emotional and reward networks.

Taking most advantages of this principle, dance therapy and rhythmic exercise can develop practical applications with higher degree [15]. Unlike conventional exercise programs that primarily target physical fitness, music-assisted movement can simultaneously stimulate motor, cognitive, emotional, and social domains. These facts seem to be the characteristic aspects of music and rhythm. Meta-analyses have demonstrated improvements in gait, balance, executive function, depressive symptoms, and quality of life among older adults participating in dance-based interventions [16]. In patients with dementia, rhythmic movement accompanied by familiar music may additionally reduce agitation, anxiety, wandering, and apathy. Consequently, it will contribute much alleviating several major components of BPSD.   Activities of mind-body interventions show benefit from neuropsychological and behavioral aspects points of view.

These multidimensional effects can be interpreted within the BHA framework [17]. Rhythmic movement enhances parasympathetic activity, increases HRV, improves cortical synchronization, and strengthens functional connectivity within large-scale brain networks, including the DMN [18]. Simultaneously, enjoyable physical activity reduces hypothalamic–pituitary–adrenal (HPA) axis activation and chronic stress. Thereby, such behavior will promote emotional stability and behavioral regulation.

Importantly, this integrated perspective emphasizes that the therapeutic value of physical activity cannot be explained solely by improvements in muscular strength or aerobic capacity. Rather, exercise may present some functions for some systems-level interventions. They simultaneously influences cardiovascular regulation, autonomic flexibility, cerebral network organization, neuroplasticity, and psychosocial engagement [19]. Such multidomain effects are particularly relevant for dementia care. It is because BPSD rarely results from a single pathological process but instead emerges through complex interactions. They include mutual influences among neurological dysfunction, autonomic dysregulation, environmental stressors, and individual psychosocial characteristics.

From mentioned above, future research should move beyond evaluating exercise intensity or duration alone [20]. Simultaneous assessment of HRV, EEG, functional magnetic resonance imaging (fMRI), and behavioral outcomes may provide a more comprehensive understanding of the mechanisms underlying non-pharmacological interventions [21]. Within this framework, the BHA offers a promising theoretical foundation for integrating cardiovascular physiology with modern neuroscience [22]. Then it may facilitate the development of personalized interventions for older adults with dementia.

In summary, meaningful relationship has been found among ANS, CNS, physical activity, dementia, MCI and BPSD from BHA point of view. The related research includes EEG, HRV, fMRI, behavioral outcomes for healthy adults and elderly with dementia and MCI. The authors hope that current report will become useful reference for future precision treatment and related research in targeting brain and cardiovascular disease prevention.

Conflict of Interest:

The authors declare no conflict of interest.

Funding:

There was no funding received for this paper.

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