Get In Tune With Chronobiology: Part Two

Did you know that you have a 70% higher chance of having a heart attack between the hours of 7 and 9 am?  That’s averaged out over the full year, but if you look from a larger level of scale you’ll find that winter months are also especially high risk.  The more I dig into Chronobiology, the tenor of my investigation has changed from simple wonderment (after all, this stuff is pretty damn cool) to more sinister speculations.  Among them is the suspicion that “Daylight Savings Time” causes epidemic levels of depression, as well as a sharp increase in accidents, both on the job and on the road.

Even thought the “facts” bear my theory out more or less completely, I just mention it in passing.  We still have a lot of ground to cover, laying out the basic mechanisms and principles behind Chronobiology.  The closer I look, the more important this material seems—whether that’s a trick of perspective or a valid point is strictly up to you.

Fractals Again

One of the major reasons I did the “Fractal Toolkit” was to provide a foundation for the next few months of Brainsturbator material.  Fractals, after all, are more than cool posters for math nerds and acid heads: they provide the most accurate mathematical tool for modeling the reality that we live in. I have been assured by people older and wiser than myself that this will take about a century to sink in, but I’m willing to keep evangelizing until that happens.

I bring up fractals here at the outset because of a quote that leaped out at me this morning over breakfast, from the uber-textbook “Chaos and Fractals”:

The view that growth and form are interrelated actually has a long tradition in biology.  In his monumental work On Growth and Form, D’Arcy Thompson traces its origins back to the late seventeenth century and comments:

“The rate of growth deserves to be studies as a nescessary preliminary to the theoretical study of form, and organic form itself is found, mathematically speaking, to be a function of time.  We might call the organism an even in space time, and not merely a configuration in space.”

Any serious contemplation of the rate of growth leads the brain to some curious landscapes.  Is there a fundamental cycle to all life, or is it more of a symphony—perhaps a cacophony of millions of different overlapping and occasionally intersecting cycles?  This puzzle is part of what led Terence McKenna to propose the existence of the “Chronon”—the fundamental unit of time, the smallest possible snapshot of “things, changing.”

Of course, perhaps that’s wishful thinking in a universe without a fundamental unit of matter or even a sense of the boundaries we exist within—assuming such boundaries exist. Either way, we will be exploring the “Chronon” concept in great depth in future articles.

Growth, Life, Time

In this chapter, the idea is given that all limitation and evil is an exceedingly rare accident; there can be no night in the whole of the Solar System, except in rare spots, where the shadow of a planet is cast by itself.

It is a serious misfortune that we happen to live in a tiny corner of the system, where the darkness reaches such a high figure as 50 per cent.

--Aleister Crowley, The Book of Lies, Commentary on Chapter 37

So, what’s the magic trick? It’s a huge system—about 93 million miles from start to finish.  Although all organisms have internal circadian clocks, what keeps them running in sync is the orbit of the Earth around the star we call Sol.  Seasonal changes in the ratio between light and darkness lead to hormonal changes in our bloodstream and in our cells.  The core pulse that all life on Earth is entrained to is the movement of the Earth itself—which on one hand is amazing, and on the other hand is pretty obvious.

As we established in the last installment of this series, newborn humans take 2-3 months to entrain themselves to the planetary cycle.  Through the brave (and perhaps insane) research of scientists like Maurizio Montalbini, we also know that humans—of any age—who remove themselves from the light/dark planetary cycle will find their internal clocks diverging considerably from the rest of the Earth.  In fact, generally within 15 days of isolation a human sleep cycle will be “off” by over 8 hours.

This has led some folks to suggest that humans aren’t native to Earth, and that’s definitely a tantalizing thought.

Meditating on the solar framework behind Chronobiology, and contemplating the Crowley quote above, I’m struck by a thought that I might not be able to fully explain.  The daytime is awash with light and everything around us becomes clear—I tended to assume that the dawn was a Great Revealing.  Likewise, night cloaks the landscape in darkness—unknown sounds become ominous, and the world around us becomes hidden.  However, the night sky allows us to actually see the cosmos surrounding us, which provides a much more clear and authentic view of where we are in the Universe.  Likewise, although we can read books in the backyard and see for miles during the day, the sunlight washing through our atmosphere is also hiding that same view of the cosmos behind a wall of blue sky.  Perhaps this is only a revelation to me, but I can’t help feeling that I understand the Taoist symbol of Yin and Yang a little better now.

How Your Brain Tells Time

Like so many great advances in science, most of what we know about the neurology of time, we learned by mutilating animals.  For some reason, hamsters have borne the brunt of our research in Chronobiology, and I would like to offer a moment of silence for their totally oblivious sacrifice. 

Even after the past decade’s explosion of neuroscience research, neurology remains a territory defined by What We Don’t Know.  However, based on What We Think We Know, the most likely candidate for “circadian pacemaker” is a small lump of tissue called the Suprachiasmatic Nucleus.  (All the literature I’ve read abbreviates that rather mouthy moniker to a mere “SCN”.) In an adult hamster, the SCN is less than 10,000 individual neurons, but some of the strongest evidence linking it to time keeping is this: when you surgically remove it from a hamster, circadian rhythms disappear almost completely.

Almost completely: there are repeated instances in multiple studies where “meal anticipation” and “body temperature” rhythms still persist even after the SCN has been chopped out.  Is that because other areas of the brain govern those rhythms?  Or perhaps because, being a robust adaptive network, the brain simply puts some other lump of neurons in charge?  Although I didn’t see it mentioned in the reports, I also wonder if sloppy surgery technique would account for these results—maybe there was enough SCN left behind to continue running the show.

The other major factor in favor of the SCN is its location: right in the hypothalamus, generally considered the “Command Center” of the mammalian brain.  The SCN also recieves nerve signals directly from the retinas, providing a clear explanation of how mammals entrain their internal cycles to the Earth as a whole.

In case anyone reading this is disturbed by the prospect of hamsters living out the rest of their lives without any circadian rhythms, you’d be relieved to know that many of these experiments had a Second Act.  As it turns out, you can implant fetal hamster brain tissue with SCN cells back into another hamster, and they will successfully graft to their brain and restore circadian rhythms completely.  Of course, that’s only a happy ending if you don’t know that lab animals are disposed of with industrial-grade blenders as a matter of policy when experiments are finished.  SORRY TO GIVE THE ENDING AWAY.

How Your Cells Tell Time

LET’S ZOOM IN A LITTLE FURTHER, SHALL WE? Are you really satisfied with the SCN explanation?  Sure, the SCN is the part of the brain that generates our circadian rhythms....but how?

This question brings us to another, much less cute, perpetual victim of lab science: the fruit fly.  Drosophila has been central to the history of genetics, because they’re easy to obtain, easy to control, and they’ve got a relatively simple genome to play with.  Another bonus is their exceptionally short lifespan—you can go through generations of Drosophila in a single month.  I have no idea why I’m compelled to share this with you, but fruit flies also hold the world record for having the longest sperm of any creature on Earth, hundreds of times larger than us humans. 

Scientists have isolated two individual genes that are responsible for the fruit fly’s biological clock—genes that also exist in most other complex organisms, so they’re currently thought to be the foundation of circadian rhythms on the cellular level.  Of course, life on the cellular level is a whole different ecosystem, one I have very little understanding of.  The most basic explanation would be the metaphor of epoxy—a mixture of two ingredients that catalyzes a chemical reaction which produces a very durable compound.  In the case of expoxy, you wind up with the Best Glue in the Universe.  In the case of circadian genetics, you wind up with compounds that take almost exactly 24 hours to metabolize and break down.

The key combination here is “per” and “tim” genes—“per” for “period”, “tim” for “timeless.” As the BMJ article “The Brain, Circadian Rhythms and Clock Genes” says:

...the human and mouse equivalents of the drosophila per gene have now been identified, and the studies showing the presence of mammalian time are likely to be published in the next few months.  The parallels between the fly and mammalian forms of the genes show that evolution has conserved not only the property of circadian timing but also its molecular basis, indicating how deeply the clock is entrenched in our genetic makeup.

If you want to really get into that report—it’s only 5 pages and I already linked to it last article—you’ll see that there’s actually even more detail: recent research has uncovered evidence that the 24 hour cycle is actually composed of 2 even smaller 12 hour cycles at a molecular level of scale.  I will, for once, recognize that I am completely out of my depth and any futher attempts at explaining the interactions of genes, proteins, and molecules would be pure hubris.

Up Next

The next installment—which hopefully won’t take as long as this one did—will focus on the role of sleep.  Sleep itself is a lot like time—we all know what it is, but nobody seems to know shit all about it.  This may or may not raise the question of “how can we possibly know what something is if we don’t know anything about it?” Of course, that’s a meta-question, and not everybody is into that stuff. 

Then again, if you’ve read this far, you’re clearly One Of Us, so I promise you, soon: The Science of Sleep.

While neither the function of sleep nor how it is regulated are completely understood, it is clear that sleep is a basic requirement that cannot be denied for very long.

Further Reading for Curious Primates

As always, I’ve found some new resources and websites that would be excessively interesting to anyone seriously exploring this material. 

The usually-excellent Science Blogs has “A Blog Around the Clock”—entirely devoted to news about Chronobiology, although the dude running it would appear to have a harder time staying on topic than I do over at Hump Jones.

Princeton Report on Circadian Rhythms—the most comprehensive and current document I’ve found.  This article would have been impossible without the overview this document provided, and if you’re looking for something to really sink your teeth into, this is the goods.

I also recently purchased Rhythms of Life, by Russell Foster and Leon Kreitzman.  I haven’t started it yet, but she came highly recommended by several people I contacted for this series.  I nearly had a lapse of sanity and ordered the 2003 textbook on the subject, Chronobiology: Biological Timekeeping, but at $80, but that’s a tad more than I’m able to invest these days.