Rhythmic Human
If you really read this blog "for the articles", especially the chronobiology articles, you are aware that the light-dark cycle is the most powerful environmental cue entraining circadian clocks. But it is not the only one. Clocks can also be entrained by a host of other ("non-photic") cues, e.g., scheduled meals, scheduled exercise, daily dose of melatonin, etc.
Clocks in heterothermic ("cold-blooded") animals can also entrain to temperature cycles. Lizards can entrain to temperature cycles (pdf) in which the difference between nightime low and daytime high temperatures is as small as…
If you discover a brain chemical which, when missing or malfunctioning (due to a mutation in its receptor) abruptly puts people and animals to sleep when they don't want to - a condition called narcolepsy - then you can work on creating a drug that acts in the opposite way and induces sleep when you want to.
Apparently, that is what a Swiss team just did (Nature news report here and Nature blog commentary here). The drug, still without a sexy name, is known by its "code-name" ACT-078573.
The target of the drug is the orexin system. Orexins (also known as hypocretins - the discovery was…
Nicole Eugene recently defended her Masters Thesis called Potent Sleep: The Cultural Politics of Sleep (PDF) on a topic that I find fascinating:
Why is sleep, a moment that is physiologically full and mentally boundless, thought to be a moment of absence and powerlessness? Where did this devalued notion of sleep come from and how can we situate sleep studies within a continuation of a historical processes and economic infuences? In other words, how does sleep effect and exist within systems of power? To answer these questions I turn to a range of scholarship and theoretical studies to examine…
I was too busy with the conference so I missed the NPR Morning Edition story on one of my favourite subjects: Adolescent Sleep, which was followed by two more stories on the same subject! I am glad to see this topic becoming this prominent.
Hat-tip: Mind Hacks
Adjust your sleep number for the best performance! Or, what does your sleep number say about your performance?
For science bloggers, a study older than a week is often too old to blog about. For scientists, last five years of literature are the most relevant (and many grad students, unfortunately, never read the older stuff). I thought that for journalists, 24-cycle was everything. Apparently not.
Northwest Explorer's 'Senior Life' columnist is having a Senior Moment, I guess. In this article about Seasonal Affective Disorder, he mentions a study that is several years old and, what's worse, has been shown to be wrong. No, the mammalian circadian clock CANNOT be reset by shining a light at the…
Here is the second guest-post by Heinrich (from March 20, 2005):
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Here is the #2 guest contribution by Heinrich (not Heindrocket) of She Flies With Her Own Wings (http://coeruleus.blogspot.com/):
Most of this post was inspired by a grand rounds / journal club given by David Dinges about two weeks ago based on years of his own research and large surveys. One line of argument in the presentation that I thought was particularly interesting - one that we as sleep researchers might want to remember when we write grants and perform our…
Well, not me, but people who know what I know. Heinrich aka Sir Oolius explains how the US military uses the knowledge of circadian rhythms and sleep in applications to torture. Just place the prisoners in a state of perpetual jet-lag and no temporal cues, then interrogate them at the time where their circadian rhythm of cognitive performance is at its lowest.
Now behind the Wall, but plenty of excerpts available in this March 26, 2005 post...
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Ha! The New York Times has this neat article, that is almost half as good as my early (and so far most frequently linked) post "Everything You Always Wanted To Know About Sleep". Here are some excerpts, go read the rest:
The Crow of the Early Bird
THERE was a time when to project an image of industriousness and responsibility, all a person had to do was wake at the crack of dawn. But in a culture obsessed with status--in which every…
How does that work? (April 03, 2005)
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Alcohol 'binges' in rats during early brain development cause circadian rhythm problems
Rats are nocturnal animals and normally begin their activity slightly after darkness sets in. The rats that had been exposed to alcohol began activities slightly before darkness set in.
When normal rats - or for that matter, humans and other animals - are in situations without environmental cues about day and night, the body's circadian clock generally drives behaviors on a cycle slightly greater than 24 hours.…
This is an appropriate time of year for this post (February 05, 2006)...
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So, why do I say that it is not surprising the exposure to bright light alleviates both seasonal depression and other kinds of depression, and that different mechanisms may be involved?
In mammals, apart from visual photoreception (that is, image formation), there is also non-visual photoreception. The receptors of the former are the rods and cones that you all learned about in middle school. The receptors for the latter are a couple of thousand Retinal Ganglion…
The original title of this post - "Diurnal rhythm of alcohol metabolism" - was more correct, but less catchy (from February 21, 2006).
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Why is breathalyzer a poor method of measuring blood alcohol levels for purposes of DUI tickets? Ed Brayton explains and links to DUI Blog with additional information.
Also, do not forget that every function in the body exhibits a circadian cycle. Likewise, alcohol metabolism:
This is from an old study, from the times when it was OK to recruit some college freshmen to drink alcoholic beverages in the name of…
A short-but-sweet study (March 18, 2006):
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I remember from an old review that John Palmer did a study on the diurnal pattern of copulation in humans some years ago. You can see the abstract here.
Now, Roberto Reffinetti repeated the study and published it in the online open-source Journal of Circadian Rhythms here.
The two studies agree: The peak copulatory activity in people living in a modern society is around midnight (or, really, around bedtime) with a smaller secondary peak in the morning around wake-time.
Dig through the papers yourself for…
Well, it's Thanksgiving tomorrow night so it's time to republish this post from last year, just in time for the ageless debate: does eating turkey meat make you sleepy? Some people say Yes, some people say No, and the debate can escalate into a big fight. The truth is - we do not know.
But for this hypothesis to be true, several things need to happen. In this post I look at the evidence for each of the those several things. Unfortunately, nobody has put all the elements together yet, and certainly not in a human. I am wondering...is there a simple easily-controlled experiment that…
Apparently, the timing of sporting events in Beijing, probably driven by needs of American TV audiences, did not take into consideration the best time of day for athletic performance. But who cares about athletes, or even about breaking Olympic and world records, when delivering Joe Schmoe to the Budweiser commercial is much, much more important for the success of Olumpic games?!
This article provides a nice summary of the issue and the current state of understanding of the way circadian clocks affect athletic performance:
Science Says Athletes Perform Better At Night
This week's Ask a ScienceBlogger question is:
A reader asks: Is severely regulating your diet for a month each year, as Muslims do during Ramadan, good for you?
There is no way I can get out of this one! As far as I know, I am the only one here who actually did research on fasting! Mind you, it's been about 5 years since I last delved deep into the literature on the effects of fasting and feeding on various body functions, mainly body temperature and circadian rhythms, but I can try to pull something out of my heels now.
I'll try to somehow systematize this, by breaking the problem down…
I tend to rant about sleep in adolescents for various reasons, but other people focus on other age groups. Infants are one such group, interesting because it takes a while for their circadian rhythms to consolidate resulting in "sleeping through the night".
For years, the only serious book on the topic was Ferber, much maligned for its advice to "let them cry it out", though the rest of the book is correct and informative. Apparently, there is a good new book on the topic - The No-Cry Sleep Solution: Gentle Ways to Help Your Baby Sleep Through the Night (as well as The No-Cry Sleep…
Nothing too complicated today, but something you should all know (from March 13, 2006).
I have mentioned this in my very first post here: in a natural state, humans do not sleep a long consecutive bout throughout the night. The natural condition is bimodal - two bouts of sleep interrupted by a short episode of waking in the middle of the night.
In today's New York Times, there is an article about this:
Sleep Disorder? Wake Up and Smell the Savanna by RICHARD A. FRIEDMAN, M.D.:
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Many patients tell me they have a sleep problem because they wake up in the middle of…
Bill Bailey reports that an organization called 'Screening for Mental Health' offers free screenings for Seasonal Affective Disorder (SAD). But then, they push drugs on people they "diagnose". The only problem - SAD is not treated with drugs!!! It is a circadian disorder, treated with light therapy and behavioral therapy. Quacks!
Study says no video games on school nights:
According to Dr. Iman Sharif, the results were clear-cut. "On weekdays, the more they watched, the worse they did," said Dr. Sharif. Weekends were another matter, with gaming and TV watching habits showing little or no effect on academic performance, as long as the kids spent no more than four hours per day in front of the console or TV. "They could watch a lot on weekends, and it didn't seem to correlate with doing worse in school," noted Dr. Sharif.
The study was using self-reporting by kids, which has its problems, but is OK in this case, I…