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Related Concept Videos

Circadian Rhythms and Gene Regulation02:19

Circadian Rhythms and Gene Regulation

The biological clock is involved in many aspects of regulating complex physiology in all animals. It was in 1935 when German zoologists, Hans Kalmus and Erwin Bünning, discovered the existence of circadian rhythm in Drosophila melanogaster. However, the internal molecular mechanisms behind the circadian clock remained a mystery until 1984, when Jeffrey C. Hall, Michael Rosbash, and Michael W. Young discovered the expression of the Per gene oscillating over a 24-hour cycle. In subsequent years,...
Midrange01:07

Midrange

A somewhat easy to compute quantitative estimate of a data set’s central tendency is its midrange, which is defined as the mean of the minimum and maximum values of an ordered data set.
Simply put, the midrange is half of the data set’s range. Similar to the mean, the midrange is sensitive to the extreme values and hence the prospective outliers. However, unlike the mean, the midrange is not sensitive to all the values of the data set that lie in the middle. Thus, it is prone to outliers and...
Circadian Rhythms and Gene Regulation02:19

Circadian Rhythms and Gene Regulation

The biological clock is involved in many aspects of regulating complex physiology in all animals. It was in 1935 when German zoologists, Hans Kalmus and Erwin Bünning, discovered the existence of circadian rhythm in Drosophila melanogaster. However, the internal molecular mechanisms behind the circadian clock remained a mystery until 1984, when Jeffrey C. Hall, Michael Rosbash, and Michael W. Young discovered the expression of the Per gene oscillating over a 24-hour cycle. In subsequent years,...
Sleep-Wake Cycles01:24

Sleep-Wake Cycles

Sleep is an essential physiological process vital to maintaining overall well-being. The reticular activating system (RAS), a network of neurons in the brainstem, regulates wakefulness and sleep. While it may seem passive, sleep consists of distinct cycles, each with its unique characteristics and functions. Two key sleep phases are non-rapid eye movement (NREM) and  rapid eye movement (REM).
NREM Sleep
NREM sleep comprises four progressive stages that seamlessly merge:
Chronopharmacokinetics: Circadian Rhythms and Influence on Drug Response01:15

Chronopharmacokinetics: Circadian Rhythms and Influence on Drug Response

Circadian rhythms are cyclic changes that are crucial in plasma drug concentrations. Various standard circadian parameters, including core body temperature, heart rate, and other cardiovascular factors, directly impact disease states and the therapeutic response to drug therapy.
The time of drug administration is an important factor to consider, as it can influence the toxic dose of a drug. For example, a study conducted by Prins et al. in 1997 examined the effects of the timing of...
Understanding Sleep01:11

Understanding Sleep

Sleep, an essential biological state, involves significant reductions in physical activity, sensory awareness, and interaction with the environment. This complex physiological process is primarily regulated by specific brain regions, notably the hypothalamus and pons, which govern the sleep-wake cycle or circadian rhythm.
The circadian rhythm, a nearly 24-hour cycle, is deeply influenced by environmental light cues. Light exposure directly affects the hypothalamus, which in turn regulates...

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Related Experiment Video

Updated: Jun 24, 2026

Noninvasive, High-throughput Determination of Sleep Duration in Rodents
07:33

Noninvasive, High-throughput Determination of Sleep Duration in Rodents

Published on: April 18, 2018

Average mid-sleep time as a proxy for circadian phase.

Thomas Kantermann1,2, Helen J Burgess3

  • 1SynOpus, Bochum, Germany.

Psych Journal
|October 17, 2017
PubMed
Summary
This summary is machine-generated.

Measuring circadian phase with melatonin is difficult. New sleep-time indices offer an easier way to estimate melatonin phase, improving subjective sleep assessments to reflect objective circadian rhythms.

Keywords:
Morningness-Eveningness Questionnaire (MEQ)Munich ChronoType Questionnaire (MCTQ)chronotypedim-light melatonin onset (DLMO)mid-sleep

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Last Updated: Jun 24, 2026

Noninvasive, High-throughput Determination of Sleep Duration in Rodents
07:33

Noninvasive, High-throughput Determination of Sleep Duration in Rodents

Published on: April 18, 2018

Collecting Sleep, Circadian, Fatigue, and Performance Data in Complex Operational Environments
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Human Circadian Phenotyping and Diurnal Performance Testing in the Real World
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Human Circadian Phenotyping and Diurnal Performance Testing in the Real World

Published on: April 7, 2020

Area of Science:

  • Chronobiology
  • Sleep Science
  • Physiological Measurement

Background:

  • Circadian phase assessment traditionally relies on melatonin measurements, which are invasive and time-consuming.
  • Existing subjective sleep-time indices offer convenience but lack accuracy in representing the objective melatonin phase.
  • A gap exists in developing practical methods to reliably estimate circadian phase from easily obtainable sleep data.

Purpose of the Study:

  • To develop and validate a novel sleep-time index for estimating circadian phase.
  • To improve the correlation between subjective sleep parameters and objective melatonin phase markers.
  • To provide a less laborious alternative for assessing circadian phase in research and clinical settings.

Main Methods:

  • Utilized data from sleep-time assessments and concurrent melatonin assays.
  • Developed a predictive model using a single sleep-time assessment to estimate melatonin phase.
  • Validated the model's performance against established melatonin-based phase markers.

Main Results:

  • A single sleep-time assessment demonstrated over 60% representation of melatonin phase.
  • The novel index significantly improved the accuracy of phase estimation compared to common indices.
  • Demonstrated enhanced ability of subjective sleep data to mirror objective circadian phase.

Conclusions:

  • A practical, single sleep-time assessment can effectively estimate circadian phase.
  • This method offers a less laborious and more accessible approach to circadian rhythm assessment.
  • Improves the utility of subjective sleep reports for understanding objective circadian timing.