{
  "abstract": "Human pupil responses vary with time of day, but whether this reflects circadian modulation of specific photoreceptor pathways is unclear. Twelve healthy adults completed repeated pupillometry during a 40-hour ultra-short sleep-wake protocol that limited sustained wakefulness; data from eight met the quality-control criteria and were analysed. This design was intended to limit progressive accumulation of homeostatic sleep pressure across sampled circadian phase. During wake episodes, 0.4-Hz silent-substitution stimuli targeted broadband flux, melanopsin, luminance, L-M cone-opponent, or S-cone pathways. Salivary melatonin provided participant-specific period estimates. We separated slow tonic constriction from phasic pupil tracking and compared hierarchical circadian cosinor models with constant-level models. Constant-level models were favoured for phasic amplitude in all five conditions (log10 BF10 = -3.36 to -1.10). They were also favoured for tonic minimum in four conditions; L-M favoured the circadian model (log10 BF10 = 0.67), but the evidence was imprecise. Under the tested contrast, adaptation, and frequency, these data do not support circadian modulation of phasic photoreceptor-directed pupil tracking. Other metrics and smaller or non-sinusoidal effects remain possible.",
  "abstract_shown": true,
  "affiliations": [
    "Max Planck Institute for Biological Cybernetics"
  ],
  "article_type": "New results",
  "arxiv": null,
  "author_total": 3,
  "authors": [
    {
      "name": "H. Heinrichs"
    },
    {
      "name": "D. Glebowicz"
    },
    {
      "affs": [
        0
      ],
      "name": "M. Spitschan"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/1r25k5gjfag7h.bib",
  "cited_by": 0,
  "doi": "10.64898/2026.10.13.758787",
  "fulltext_url": "https://www.biorxiv.org/content/10.64898/2026.10.13.758787v1.full",
  "id": "1r25k5gjfag7h",
  "issns": [],
  "landing_url": "https://www.biorxiv.org/content/10.64898/2026.10.13.758787v1",
  "language": null,
  "licence": "CC-BY",
  "licence_label": "CC BY",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "biorxiv",
      "neuroscience"
    ],
    [
      "openalex",
      "2807|Circadian rhythm and melatonin"
    ]
  ],
  "openalex": "W7222938847",
  "pdf_url": "https://www.biorxiv.org/content/10.64898/2026.10.13.758787v1.full.pdf",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-13",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/1r25k5gjfag7h.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:28:36Z",
      "native_id": "10.64898/2026.10.13.758787",
      "source": "biorxiv",
      "url": "https://www.biorxiv.org/content/10.64898/2026.10.13.758787v1"
    }
  ],
  "subjects": [
    {
      "field": "biology",
      "origin": "biorxiv:neuroscience",
      "subfield": "neuroscience"
    }
  ],
  "title": "Phasic pupil responses to melanopsin- and cone-directed stimulation remain stable across circadian time",
  "title_text": "Phasic pupil responses to melanopsin- and cone-directed stimulation remain stable across circadian time",
  "type": "preprint",
  "updated_at": "2026-10-30T12:28:36Z",
  "url": "https://research.draconitic.com/paper/1r25k5gjfag7h",
  "venue": "bioRxiv",
  "versions": []
}