ultradianadj.
/ʌlˈtreɪdɪən/, U.S. /ˌəltrəˈdiən/ Designating cycles of physiological activity which recur with a period shorter than one day but longer than one hour. Cf. circadian adj.
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ultradian1961
1961 F. Halberg in 39th Rep. Ross Conf. Pediatric Res. 15 Observations have been made on frequencies higher than circadian, yet lower than the respiratory or cardiac cycles (ultradian), and frequencies lower than circadian, but higher than the menstrual cycle (infradian).
1978 Nature 3 Aug. 490/1 In humans, REM sleep..occurs every 90–110 min and is presumed to be under the control of an underlying ultradian oscillatory mechanism.
This entry has not yet been fully updated (first published 1986; most recently modified version published online March 2022).
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adj.1961