{
  "id": 7390525,
  "title": "The Asymmetrical Architecture of Ultradian REM Sleep: Direction, NREM Currency, and a Finite Post-REM Predictive Horizon in Mice",
  "url": "https://urgent.news/2026/09/14/the-asymmetrical-architecture-of-ultradian-rem-sleep-direction-nrem",
  "topic": "finance",
  "section": "Finance & Markets",
  "published": "2026-09-14T00:00:00.000Z",
  "source": {
    "name": "bioRxiv",
    "slug": "biorxiv",
    "url": "https://www.biorxiv.org/content/10.64898/2026.09.08.750050v1?rss=1"
  },
  "original_language": "en",
  "account": "The research delves into the intricate structure of ultradian REM sleep in mice, challenging previous theories on the controlling variable of the sleep cycle. The investigators reanalyzed 24-hour recordings from 25 mice, focusing on the direction of REM sleep, the structure of post-REM suppression, the currency of the interval, and the overall macro-organization of REM output.\n\nTo achieve this, the researchers reconstructed REM episodes and inter-REM intervals from 15-second vigilance scoring, resulting in 1,955 valid intervals. They employed a variety of statistical models, including mixed-effects models, lower-quantile regression with leave-one-mouse-out validation, within-mouse permutation, discrete-time hazard models, and held-out-mouse comparison of accumulated NREM against elapsed time.\n\nThe results unveiled a critical asymmetry in the ultradian REM organization. The findings indicate that preceding REM duration (REMpre) positively predicts subsequent NREM accumulation, with a strong positive correlation (rho=0.506) in all 25 mice. The relationship follows a convex pattern, where for each minute of REMpre, an approximate of 1 minute of NREM accumulates. However, this relationship is not a strict refractory floor, but rather a graded constraint with a lower envelope that relaxes over time, allowing a few minutes of NREM recovery after approximately 10 minutes of accumulated NREM.\n\nThe study also discovered that the effect of preceding REM on NREM accumulation becomes undetectable beyond approximately 10 minutes of accumulated NREM. Furthermore, the hazard of episode termination increases with episode duration, following a Weibull shape of 1.48. Importantly, the variability in the number of REM episodes among individual mice was four times greater than the variability in the mean duration of these episodes.\n\nIn conclusion, the research underscores the strong asymmetry in ultradian REM organization. The preceding REM imposes an early constraint that shapes the subsequent NREM accumulation in a graded fashion, with a clear lower envelope, a brief recovery period, and a finite predictive horizon near 10 minutes.",
  "summary": "Study Objectives: Competing accounts of ultradian REM sleep place the controlling variable either before or after the REM episode. We reanalysed 24-hour recordings from 25 mice to test directionality, the structure of post-REM suppression, the currency of the interval, and the macro-organization of REM output. Methods: REM episodes and inter-REM intervals were reconstructed from 15-s vigilance…",
  "key_points": [],
  "editors_take": null,
  "illustration": null,
  "coverage": {
    "outlets": 1,
    "also_reported_by": []
  },
  "ai_generated": true,
  "disclaimer": "Summaries, key points and the editor’s take are written by software from other outlets’ reporting and may contain errors — always check the linked original."
}