Episodic Ultradian Events—Ultradian Rhythms

Abstract

In the fast lane of chronobiology, ultradian events are short-term rhythms that have been observed since the beginning of modern biology and were quantified about a century ago. They are ubiquitous in all biological systems and found in all organisms, from unicellular organisms to mammals, and from single cells to complex biological functions in multicellular animals. Since these events are aperiodic and last for a few minutes to a few hours, they are better classified as episodic ultradian events (EUEs). Their origin is unclear. However, they could have a molecular basis and could be controlled by hormonal inputs—in vertebrates, they originate from the activity of the central nervous system. EUEs are receiving increasing attention but their aperiodic nature requires specific sampling and analytic tools. While longer scale rhythms are adaptations to predictable changes in the environment, in theory, EUEs could contribute to adaptation by preparing organisms and biological functions for unpredictability.

Ultradian Rhythms in Heart Rate Variability and Distal Body Temperature Anticipate the Luteinizing Hormone Surge Onset

“…The premise of the present investigation is that the presence of structured changes to peripheral biological rhythms across the menstrual cycle may allow for anticipation of the LH surge. Such a finding would further support the notion that the state of one system (e.g., reproductive) can be inferred via measurements of another (e.g., autonomic or metabolic) (Shannahoff-Khalsa et al, 1996;Grant et al, 2018;Goh et al, 2019). Perhaps the most consistent biological rhythmic changes across the menstrual cycle occur at the 1-4 h (ultradian) timescale (Brandenberger et al, 1987;Shannahoff-Khalsa et al, 1996, 1997Grant et al, 2018;Zavala et al, 2019).…”

“…The band of the wavelet matrix corresponding to 2-5 h rhythms were averaged in order to create a linear representation of UR WT power over time. This band corresponded with the daily ultradian peak power observed in URs across physiological systems (Brandenberger et al, 1987;Grant et al, 2018;Goh et al, 2019). Potential changes to circadian power of DBT (average power per minute within the 23-25 h band) were additionally assessed prior to extracting days for ultradian-only analyses, but no significant changes across the cycle were detected (see Supplemental Figure 3).…”

“…These peripheral and endocrine measures are proposed to operate as coupled oscillators at the ultradian time scale. Assessment of these measures could therefore, potentially enable endocrine status assessment via timeseries analysis of peripheral measures (Shannahoff-Khalsa et al, 1996;Grant et al, 2018;Goh et al, 2019).…”

Impact of Sleep Deprivation on Emotional Regulation and the Immune System of Healthcare Workers as a Risk Factor for COVID 19: Practical Recommendations From a Task Force of the Latin American Association of Sleep Psychology

“…Episodic Ultradian rhythms have been defined as periodic rhythms that last for 20 min to 6 h, such as the patterns of the electrical activity of the brain and the heart. The functional significance of ultradian events might be in optimizing biological activities mainly by synchronizing compatible processes and preventing the simultaneous activation of incompatible processes, preparing biological systems to respond to stimuli such as cell-cell communication, and interacting with circadian rhythms ( Goh et al, 2019 ).…”

Does damage to hypothalamic paraventricular nucleus underlie symptoms of ultradian rhythm disorder and an increased anxiety in coronavirus disease 2019?

“…The PVN is an important ultradian master oscillator that has been proposed to regulate BRAC and the body’s physiological responses to psychological and physical stress by initiation of a hormone cascade that eventually alters physiological and metabolic states ( 9 , 10 ). Its role in modulation and triggering of the trigeminal autonomic cephalalgias by mediating the regulation of nociceptive and autonomic input, has similarly been proposed.…”