Wednesday, April 29, 2009

Forced Desynchronization

First time somebody complained to me about their jetlag it was my grand-aunt. I assumed she had a problem with her leg. After more than five years in a transatlantic relationship, "jetlag" has become one of my more frequent answers to the question how I am doing. I would describe it as a desorientation of my inner clock that typically results in sleeping problems despite tiredness, accompanied by headaches, low blood pressure and a generally bad mood.

Now I recently came across this interesting paper

presenting the results of experiments on rat that were subject to an increased daylight period, similar in duration to that on a flight from Central Europe to the East Coast. The rats had previously been on an artificial day-night cycle with 12 hours light and 12 hours darkness. Then their daylight period was increased by 6 hours, followed by a 12 hour night, another 12 hour day and then complete darkness. Among other things, the rats were implanted with EEG electrodes recording their brain activity.

The authors study two different sleep phases in this experiment: the so-called Slow-Wave-Sleep and the REM (rapid eye movement sleep). They can be distinguished by brain activity. The sleeping pattern is regulated by a brain region called the suprachiasmatic nucleus  responsible for the roughly 24 hour rhythm of living organisms. It consists of two areas, the ventrolateral and dorsomedial part. The ventrolateral part obtains light information from the eye, the dorsomedial part doesn't. Exposing the rats to a longer period of daylight leads to an "enforced desynchronization" of these two regions. 

The measurements of brain activity show that while the the slow-wave-sleep immediately adjusts after the delay of the next night phase, the REM sleep needed several days to come back in synch with the slow-wave-sleep, indicating that the former is regulated by the ventrolateral, the latter by the dorsomedical suprachiasmic nucleus. In the meantime, the sleep architecture of the rats was messed up.

Reading the paper I had been wondering why, after increasing the light-period, the day-night cycle was not continued but instead the rats were put into total darkness while measurements were continued. Horacio de la Iglesia, one of the authors of the paper, was so kind to answer my question and explained that previous research had shown that in such a way the dysynchronization continues to 6-7 days, whereas with a continued day-night cycle the readjustment might happen faster. 

I find this study really interesting. Of course there are many reasons why this experiment on rats doesn't too accurately describe what happens in the human brain when jetlagged, but I think chances are good the basic insights about the messed-up sleep patterns are transferable. There are many further questions that spring into mind, for example one would like to know if the desynchronization lasts longer if instead of increasing the daylight period, the nighttime period is decreased. That's because I find it typically much harder to adjust after an eastward than after a westward flight. After reading the paper I believe it might be because in this case I tend to sleep into the day too long, missing many hours of sunlight which delays adjustment further. One would also like to know how the time needed for adjustment relates to the phase shift in the day-night cycle.

Something else I learned from this paper is that "sacrificing" (in this case the rat) is an euphemism for "chopping off their head and removing their brains". 

14 comments:

Plato said...

While I do not ever have the need to encounter Jet Lag I know the problem well.

Circadian rhythmSome studies have shown that a short period of sleep during the day, a power-nap, does not affect normal circadian rhythm, but can decrease stress and improve productivityCircadian rhythmThis is a consequence I think people should not put lightly as it can most certainly help with above dispositions. Affecting later sleep times can be an issue if more then a nap turns into a couple of hours.

Caffeine in coffee and other things before sleep times have to be watched for too.

Some might of seen the odd posting times of my entries are because of working shift work for the past 35 years.

The physiological effects as you experience them, I experience them too. Even after many years, every time I tried to change my biological clock, trying to come back "into some kind of sequence" I found was very hard.

Best,

Plato said...

Just as aside note for consideration, the idea of an "embedded oscillation" might be one to consider as it spreads through the psychologies and philosophies.

Maybe not seen by many as, such a dance, it is spread all through nature as "shadows and light," and this would seem to me to be part of our makeup as well.

Abstract, as it might seem "a line," of shadow or light, is a powerful recognition of any line defined? Balance.

Quantum Harmonic Oscillators.

Best,

stefan said...

Dear Bee,

thanks for the update! Poor rats, so their jetlag is extended artificially by keeping them in the dark... but it's great that one of the authors has answered your question and explained some details of the experiment.

Cheer, Stefan

Arun said...

Presumably the rats were in a constant temperature environment? I wonder what role that plays.

As an aside, apparently some plants, birds, etc., in the spring respond to the temperature, while others respond to the light. So a mismatch appears along with global warming, kind of like the dorsomedial and ventrolateral suprachiasmic nucleus :)

Bee said...

It doesn't explicitly say in the paper what the temperature was, or at least I can't find it, but I suppose it was constant.

What factors about light are plants receptive to? Isn't the intensity of light correlated to some extend to the temperature in that during spring/summer both tend to be lower if it's more cloudy and both higher if it's blue skies?

Count Iblis said...

While in Europe you should sleep from 3 am to 11 am.

Arun said...

Bee, pardon the imprecision. Some things respond to temperature others to length of day.

Kris Krogh said...

Hi Bee,

Of course the Sun is the master clock to which our circadian rhythms are entrained. Experiments with artificial environments lacking time-of-day cues show the internal clocks of typical humans free run on a sleep-wake cycle of about 25 hours.

The system relies on morning sunlight to sync the internal clock to the Sun. (Melatonin levels drop in response to sunlight, then rise in the evening and cause sleepiness.) The lagging internal clock makes a lengthened cycle traveling west easier than a shortened one traveling east.

Going east to Europe, I drop a melatonin tablet in the evening for a few days, and force myself outside in the morning sun. It helps.

Cheers, Kris

Phil Warnell said...

Hi Bee,

Thanks for sharing your discovery of this paper. As Plato pointed out shift workers experience jet lag, yet by a different mechanism and it has proven to be very stressful on people in particular when they change shift. It also interesting to learn that it is our REM sleep that is the most effected in such periods, thereby shortening our dreams. There are lots of theories that consider that our dreams are very important to our cognitive process, along with our mental stability. It would be nice then if they studied more the relationship between the amounts of quality REM sleep one gets as it correlates to general creative ability. It would be also interesting if we could develop techniques to allow us to focus our REM periods to have us become more effective cognitively.

As the old saying proclaims it is important one gets their “beauty rest”, which I would equate with slow wave sleep, which in turn aids to repair the body. On the other hand REM helps to freshen our minds to be able to better solve problems. Perhaps this then should be called “truth sleep”, which this study indicates to be as important if not more so then “beauty rest”. This is to remind of course a proper balance must be struck between both truth and beauty. So I find it interesting indeed that after many millennia such things appear to still hold significance today.

Best,

Phil

Plato said...

Just to carry on with Phil's thinking even more, shall we use the excuse to "proclaim a right for our psychological responses" in the daylight of the working world?

So you look to build "stability" no matter the weather outside. No matter how stormy the seas.

A central core of thinking that is unaffected by such biological changes., as an effective realization about encapsulating memory?

Whilst this goes on in the body you become aware of these changes and adapt. Understand emotive consequences that are ignited by biological changes. Heart rate, temperature. A mode of thinking?

If we die with a peaceful mind, this will stimulate a virtuous seed and we shall experience a fortunate rebirth; but if we die with a disturbed mind, in a state of anger, say, this will stimulate a non-virtuous seed and we shall experience an unfortunate rebirth. This is similar to the way in which nightmares are triggered by our being in an agitated state of mind just before falling asleep.It is not every about dying, but about "how one chooses to live." That we can "die continually" in any moment and be reborn. Whether you believe in a rebirth or not, this has consequences taken within that process to endorse "an creative aspect within the perfect realm of problem solving."Would you rather be "less then in control" or more weathered" then to relinquish oneself to the experience the nightmare?

Phil Warnell said...

Hi Plato,

“Just to carry on with Phil's thinking even more”

I’m not certain if this is the direction to where I was leading, more a wish to understand what potential is held within the dreams we have and how they might serve us better if the mechanism, purpose and control of them became more clear and better understood. As for what if anything is to be expected after I must admit still to more relate with Hamlet then the Dalai Lama. One thing for certain though is if anything is to be discovered, as to be known it will be regardless of how much we understand before and only relevant if there be an after. So here only the objective will count as the subjective will depend entirely upon it. So until then I’m more curious to know what we can make good of the dreams from which we more usually awake and for which knowledge of we lag behind:-)

“To die, to sleep; to sleep, perchance to dream. Ay, there's the rub, For in that sleep of death what dreams may come,when we have shuffled off this mortal coil, must give us pause................. But that the dread of something after death, The undiscovered country from whose bourn No traveller returns, puzzles the will, and makes us rather bear those ills we have than fly to others that we know not of? Thus conscience does make cowards of us all."

Hamlet-Act 3, Scene 1-William ShakespeareBest,

Phil

plato said...

Phil:It would be nice then if they studied more the relationship between the amounts of quality REM sleep one gets as it correlates to general creative ability. It would be also interesting if we could develop techniques to allow us to focus our REM periods to have us become more effective cognitively.:)

plato said...

All The World's A Stage by William Shakespeare
From: As you Like It, Act II Scene VII

Jaques:All the world's a stage,
And all the men and women merely players:
They have their exits and their entrances;
And one man in his time plays many parts,

Georg said...
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