Sleep and Memory | Part 2

The second half of Why We Sleep starts like this “Amazing breakthrough!  Scientists have discovered a revolutionary new treatment that makes you live longer.  It enhances your memory and makes you more creative.  It makes you look more attractive.  It keeps you slim and lowers food cravings. It protects you from cancer and dementia.  It wards off colds and the flu.  It lowers your risk of heart attacks and stroke, not to mention diabetes.  You’ll even feel happier, less depressed and less anxious.  Are you interested?”

Hyperbolic as this may seem, nothing about this fictitious advertisement is inaccurate when it comes to sleep.

All the notes I highlight on sleep below are related to scientific studies performed by Matthew Walker and his team, or others in the scientific community.  For ease of writing and reading flow, I won’t note the sources here but I’ll give you the page in the book which elaborates in each case and the book index contains all of the sources.

 

SLEEP AND LEARNING

  • Which sleep confers the greater memory savings benefit? (deep NREM or REM)?  An early night, right in deep NREM. (p113)
  • Experimental results of Jenkin and Dallenbach have now been replicated time and time again with a memory retention benefit of between 20 and 40 percent being offered by sleep, compared to the same amount of time awake. (p113)
  • The more sleep spindles an individual obtains during a nap, the greater the restoration of their learning when they wake up (p110)
  • In 2006 a team in Germany ran a study to insert small amounts of electrical voltage during deep sleep.  When done pulsing in rhythmic time with the brain’s own waves, both the size of the brain waves and the number of sleep spindles were increased by the stimulation and provided a memory enhancement of 40% over the control group. (don’t try this at home!) (p117)
  • A swiss team suspended a bed frame on ropes and rocked the bed from side to side at controlled speeds.  Slow rocking increased the depth of deep sleep and boosted the quality of slow brain waves and more than doubled the number of sleep spindles.  (p118)
  • Using MRI scans, scientists have since looked deep into the brains of participants to see where those memories are being retrieved from before sleep relative to after sleep.  Information packets are recalled from completely different locations. Before sleep, participants fetch newly learned information from the hippocampus.  After sleep, from the neocortex. (p114)
  • Sleep stimulation efforts to date are indiscriminate – that is, you can’t really choose what to remember or what to forget. Science now has a new method called “targeted memory re-activation”.  Before going to sleep in this test, participants were shown not just images at different locations and this would be accompanied with a sound (e.g. a meow for an image of a cat).  When asleep, participants were played back the sounds on low volume with speakers at either side of their bed.  The memories recalled the next day were biased significantly toward those reactivated during sleep using the sound cues. This is the type of thing you could use for some SERIOUS brainwashing. (p119).
  • In another experiment, when participants were given words to remember as well as an indicator as to whether to remember or forget the word, after sleep (vs the non sleep group), memory was selectively boosted for those that had been tagged to be remembered.
  • Which stage of sleep determines what memories should be priorities vs removed? NREM sleep – and the very quickest of sleep spindles.  Eternal Sunshine Of the Spotless Mind here we come! (p122)

 

SLEEP IMPACT ON OTHER TYPES OF MEMORY

  • The term “muscle memory” is a misnomer.  Muscles themselves have no suc memory: a muscle that is not connected to a brain cannot perform any skilled actions, now does a muscle store skilled routines.  Muscle memory is, in fact, brain memory. Training and strengthening muscle can help you better execute a skilled memory routine, but the memory routine, the memory program – resides exclusively in the brain. (p123)
  • In an experiment teaching right handed people to type a number sequence with their left hand, those who slept showed a 20% jump in performance speed  and a 35% improvement in accuracy vs those who were tested before bed.  Those then tested before bed were re-tested in the morning and got the same bump in performance.  So the brain keeps improving skill memories without practice. (p125)
  • When the brain transfers skill memories, its not look fact / info based memory, the motor memories are shifted to brain circuits that operate below the level of consciousness.  (p127)
  • The type of sleep responsible for overnight motor skills enhancement is directly related to the amount of stage 2 NREM, especially in the last two hours of an eight hour night of sleep. (p127)

SLEEP IMPACT ON SPORTS

  • The less sleep an athlete has, the higher the the likelihood of injury.  At 6 hours average, the change of injury is 72%. What!!  Compared to just 18% at 9 hours average sleep or 35% at 8 hours average sleep. (p129)
  • One example of this is the difference in an NBA player’s stats when measuring performance on games played on nights after 8 hours or more vs those with less than 8 hours (p130):
    • 8 hours or more:
      • +12% increase in minutes played
      • +29% increase in points/minute
      • +2% increase in three-point percentages
      • +9% increase i free-throw percentage
    • Less than 8 hours:
      • +37% increase in turnovrs
      • +45% increase in fouls committed
  • At the most dramatic time of motor learning in any human’s life (when we learn to stand and walk as an infant), there is a consistent spike in stage 2 NREM sleep, incring sleep spindles, right around the time of transition from crawling to walking. (p131)

 

I’m splitting these posts into more parts so you can read it sooner – as at my current rate it might take me a couple of weeks to get through all the notes.  The next post will be on the impacts of sleep deprivation and health outcomes and then we’ll move on to the awesome world of dreams!

Advertisements

The Politics of Hormones

For the last two days every human being and animal I’ve crossed paths with has pissed me off.  And I can’t control it.  It was only when my partner gingerly pointed out one day that I seem to want to kill myself (or everyone else) on the same 3 days every month, that I realised that it was overwhelmingly brought on by my monthly hormone cycle.

Double-flowered carnationsThis morning I attempted to make myself feel better by having a healthy breakfast, buying some carnations and painting each fingernail a different colour of the rainbow.  It turns out chucking a hissy fit and have a rage-fueled cleaning spree did the trick instead.  As I was attempting to stuff these beautiful carnations into a ridiculously narrow vase, one of the flower heads popped off and I quickly realised this vase just wasn’t going to work and tension began to build.  I pulled the stems out and briefly glanced around the room only to be struck by the vision capabilities of a vampire, zeroing in on thousands of grotty specs of dust.  The kitchen was a pigsty.  The tension burst.  I screamed and threw the flowers stems across the room like a two year old.  Thankfully no one else was there to witness it.

And there you have it – human hormones in action.  Have too little of one and you become depressed, too much of another and you’re angry.  These regulatory substances that our own bodies produce, sometimes in cycles, sometimes in response to medications or environment, are created and then transported by our blood to stimulate specific cells or tissues into action.  Basically, they’re little chemical messengers that help to keep everything in balance.  Testosterone, Estrogen, Insulin, Oxytocin and even Dopamine as a peripheral hormone – over 50 of them in total.

But as anyone who has attempted to live a balanced life knows…balance is not exactly simple, it’s a constant juggling act.  So here’s my poor female  body, prepping itself to make babies every month while the rest of me has to catch up and balance all its internal chemicals just right to keep me sane.  I’m lucky it can at least do that.

Many of us would like to think we have absolute final control over our actions and disposition, but our predisposition toward certain behaviours or traits are governed by these chemical compounds which are originally a product of genetics or epigenetics, but then subject to change based on our own epigenome and our environment.  For instance, what we choose to eat or not to eat (given foods are also chemicals), will also effect the chemical composition of our guts and our bodies.  Here’s some examples of the power of hormones:

  • Pre-op Female Transexuals take more Estrogen to stimulate breast formation, heightening of voice and change of fat distribution across the body although this cannot change the effects of the androgens (testosterone and others) on the shape of the skeleton. Visa versa for Pre-op Male Transexuals.
  • Men who take more anabolic steroids like testosterone to make bones stronger and muscles bigger can have the side effect of high blood pressure, sharp aggressive moods, increase in body heat and reduced sperm count.Chemical structure of oxytocin.
  • Oxytocin has different effects in men verses women.  In men it improves the ability to identify competitive relationships whereas in women it facilitates the ability to identify kinship.  It is released by the body in high doses during pregnancy and around childbirth in order to ensure proper boding between the mother and the child and it is also released during sex, which is why women tend to interpret sex as having more meaning than males do, because while it can also be released in men – the presence of testosterone interferes with its release.
Cover of "Emotional Awareness: Overcoming...

Cover via Amazon

I have been reading Emotional Awareness which is a book that covers a 3 week conversation between the Dalai Lama and scientist Paul Eckman (who is behind vast tomes of research on human emotion and, in particular, how it is expressed in minute facial expressions.  His work formed the basis of the TV show “Lie to Me”). In the book they talk about the difference between moods and emotions – where a mood is generally not tied to a specific event or circumstance but has a continuous emotional effect, whereas an emotional episode is much more able to be linked to a trigger event.  In some ways, moods trigger emotional episodes that reflect the mood itself, while emotional episodes are often in response to some sort of external trigger.

When I look at this in the context of hormones, I can see how hormones would often be the precipitants of moods, which would then trigger a variety of emotional responses.  The stronger the hormone and stronger the mood, the stronger the emotional response, and of course like all learned human behaviour, these patterns would continue to strengthen over time if performed again and again and can be how people slip into ongoing depression or aggression.

All this also got me thinking about how religion deals with hormones and their effect on humans.  Two particular instances I can think of relate specifically to women:

  1. In Sharia (Islamic) law, two women must bear witness to a crime in order to be heard in court.  This is stated to be due to the emotional nature of women, although on further research I found the story was related directly to Mohammad wanting to save one of his wives from being stoned to death by being caught all one with another man by a woman.  It seemed he often made up rules to suit his worldly purposes.
  2. In Jewish law, a man cannot touch a woman who is in the bleeding section of her monthly cycle.

Interestingly, there seems to be no similar law governing the display of aggression in men which is similarly a hormone fueled disposition.  Perhaps from an evolutionary perspective this is because the male aggression hormone was highly useful during times of empire expansion and the need to protect land, while the female hormal response in its monthly cycle had no broader benefit (from the patriarchs perspective).

Because for the majority of history, both East and West have lived in patriarchal societies, the best way to look at hormones being a determinant of military and political outcomes is through a male sex hormone like Testosterone.  As an example, research in 1992 showed there was no difference in Testosterone levels between black and white boys during adolescence, but in adulthood, black male testosterone levels were much higher which then directly links to other statistics we see on the number of incarcerations of black verses white males.  Of course there are so many other factors involved including race related discrimination and levels of education…etc but hormones remain a factor.  For instance in contrast, there was significant racism in Western countries toward those of Chinese descent and yet their incarceration rate remains lower.  So if we widen out that thinking from groups to countries, we see the possibilities for testosterone levels in any particular age generation to change and potentially fuel the ability for one clan (or country) to change military outcomes, or to resort to military resolutions over negotiation.  Environmental factors also come into play with research showing in adult male rats that experience short term starvation can significantly reduce testosterone levels.

So here we have a mix of chemicals in our bodies which have the potential to guide us to achieve great good or great destruction and yet we have only scratched the surface in controlling their effects through various hormone replacement therapies that often have many unwanted side-effects of their own.

Fitbit: Wireless Personal Trainer

Fitbit: Wireless Personal Trainer (Photo credit: mrcd@sbcglobal.net)

Interestingly I recently did an interview with Jonathan Teo as part of a Fireside chat run by our meetup group Lean Startup Melbourne.  He led initial investor rounds into Twitter and Instagram and more recently Snapchat and is one of the key people in the tech industry who has been able to predict new technology trends.  One of the key trends being talked about in the tech industry at the moment is wearable tech (being able to monitor body functions insitu) – which is in part being quickly moved forward and expanded by breakthroughs in nanotechnology and size/power of computer chips.

At our last meetup, one of the speakers was from Lab on a Chip in Melbourne who talked about the real possibility in the near future of capabilities being produced that would enable the immediate mapping of genomes and epigenetic markers and then the smart releasing of medications or hormones through a patch (just like a smoking patch…but way smarter!).
Here’s hoping there’s a nanotech-hormone-patch for PMS before I smash a plate….or five.