{
  "abstract": "Cardiac autonomic activity is observed only through beat-to-beat (RR) intervals, and separating it into parasympathetic-like and sympathetic-like components is an inverse problem that RR alone is not expected to solve uniquely. We introduce SPARK (Stochastic Phase-domain Autonomic Reconstruction Kinetics), a state-space model in which two independent, mean-reverting latent drives modulate heart rate through an integrate-and-fire pacemaker. The model is combined with exact continuous-time Kalman filtering and with an explicit physiological identification structure: time-scale priors, a kinetic ordering and a spectral partition of heart rate variability. SPARK offers a model-conditional description of autonomic trajectories that complements conventional heart rate variability; its latent states are reconstructions, not measurements of neural activity. Across recordings, fitting each recording from many different starting points gave a median of 23.5 distinct solutions without physiological information versus 1.0 with it, and one process absorbed essentially all the variability in 75% versus 4% of the fits; the fit diagnostics showed residual structure in most recordings. Reconstructions were then examined: in 10 tilt-table recordings, the vagal-like state decreased and the sympathetic-like state increased in 10 of 10; exploratory comparisons between 20 young and 20 older adults showed differences in reconstructed variability and faster-component kinetics, although several latent summaries were mathematically redundant; and in 263 exercise recordings, median recovery times, which are closely tied to the fitted time constants, were 42 s (vagal-like) and 341 s (sympathetic-like). How a stressor-induced change is split between the two drives remained sensitive to the spectral anchor.",
  "abstract_shown": true,
  "affiliations": [
    "Universidad de Magallanes"
  ],
  "article_type": "New results",
  "arxiv": null,
  "author_total": 3,
  "authors": [
    {
      "name": "M. Castillo-Aguilar"
    },
    {
      "name": "N. Beelders"
    },
    {
      "affs": [
        0
      ],
      "name": "C. Nunez-Espinosa"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/at0190f7wgmje.bib",
  "cited_by": 0,
  "doi": "10.64898/2026.11.06.764976",
  "fulltext_url": "https://www.biorxiv.org/content/10.64898/2026.11.06.764976v1.full",
  "id": "at0190f7wgmje",
  "issns": [],
  "landing_url": "https://www.biorxiv.org/content/10.64898/2026.11.06.764976v1",
  "language": null,
  "licence": "CC-BY-NC-ND",
  "licence_label": "CC BY-NC-ND",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by-nc-nd/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "biorxiv",
      "physiology"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://www.biorxiv.org/content/10.64898/2026.11.06.764976v1.full.pdf",
  "pmcid": null,
  "pmid": null,
  "published": "2026-11-06",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/at0190f7wgmje.ris",
  "sources": [
    {
      "first_seen": "2026-11-10T00:28:02Z",
      "native_id": "10.64898/2026.11.06.764976",
      "source": "biorxiv",
      "url": "https://www.biorxiv.org/content/10.64898/2026.11.06.764976v1"
    }
  ],
  "subjects": [
    {
      "field": "medicine",
      "origin": "biorxiv:physiology",
      "subfield": "physiology"
    }
  ],
  "title": "SPARK: Physiology-informed inference of latent cardiac autonomic dynamics from RR intervals",
  "title_text": "SPARK: Physiology-informed inference of latent cardiac autonomic dynamics from RR intervals",
  "type": "preprint",
  "updated_at": "2026-11-10T00:28:02Z",
  "url": "https://research.draconitic.com/paper/at0190f7wgmje",
  "venue": "bioRxiv",
  "versions": []
}