Sleep, Tetris, Memory and the Brain
As part of our ongoing Author Speaks Series, we are honored to present today this excellent article by Dr. Shannon Moffett, based on her illuminating and engaging book. Enjoy!
(and please go to sleep soon if you are reading this late Monday night).
Two years ago I finished a book on the mind/brain, called The Three Pound Enigma: The Human Brain and the Quest to Unlock its Mysteries . Each chapter profiles a leader in a different aspect of mind/brain research, from neurosurgery to zen Buddhism, from cognitive neuroscience to philosophy of mind. One of my subjects was Dr. Robert Stickgold, a zany, hyper-intelligent mensch of a Harvard sleep researcher. When I met him, I was in medical school and having a grand old timeÃ¢â‚¬â€IÃ¢â‚¬â„¢d exacted an extension of my tenure beyond the customary four years, so I had enough time to write the book, do my coursework, and have a life. I was busy, but still got enough sleep, had time to exercise daily, and even went for dinner and a movie sometimes. Although I found StickgoldÃ¢â‚¬â„¢s work interesting, there was a part of me that just didnÃ¢â‚¬â„¢t get it.
Fast-forward to the present, when I am a resident in emergency medicine at a busy inner-city trauma center; I have two-year-old twins and a husband with a 60-hour-a-week job of his own. I do not exercise. I do not eat unless I can do something else productive at the same time, and even when I do get to sleep in my own bed, my slumber is fractured by the awakenings of two circadianly disparate toddlers. It seems to take me twice as long to Ã¢â‚¬Å“getÃ¢â‚¬Â new concepts as it used to, and I never feel like IÃ¢â‚¬â„¢m functioning at top speed. In short, I am a mess. And NOW I get what StickgoldÃ¢â‚¬â„¢s work is all about, and understand that he is both quantifying and explaining exactly what IÃ¢â‚¬â„¢m feeling.
Sleep is so obvious a physiologic need (from insects to mammals, all animals sleep) that it doesnÃ¢â‚¬â„¢t even occur to most of us to wonder why we have to do itÃ¢â‚¬â€why in the world would we need to lie down, paralyzed, for a third of our lives, with our brains in some sort of auto-pilot chaos? What do we get out of the process? It is astonishing how sparse is scienceÃ¢â‚¬â„¢s answer to that question, but Stickgold and others are beginning to provide a solution, and their answer ought to make any of us who are interested in mental fitness sit up (or rather, lie down) and take notice.
When I met him, Stickgold was just hitting his stride in what would turn out to be his specialized area of researchÃ¢â‚¬â€the connection between sleep and cognition, and in particular, between sleep and memory. I had become interested in his work partly because he was using non-traditional research tools: while many neuroscience experiments involve setting their subjects tedious made-up tasks, Stickgold had heeded the suggestion of one of his undergraduate research assistants and was using video-games as his mental challenges.
Using the computer-game Tetris heÃ¢â‚¬â„¢d found what many of us knew anecdotally: that just as they fall asleep after long Tetris practice sessions, players hallucinate images of the peculiarly-shaped Tetris tiles drifting down their fields of vision. It turns out, Stickgold found, that even subjects with severe amnesia, who couldnÃ¢â‚¬â„¢t recall having played the game at all, had the same experience. He hypothesized that those images must have something to do with a particular kind of skill memory, known as procedural memoryÃ¢â‚¬â€ the type of physical memory created when you practice the violin, or learn to play tennis, or write calligraphy. This type of memory is often preserved even in people with severe amnesia. It seems likely that sleep is serving to somehow organize this type of memory. And it turns out that without any further practice, the subjects showed improvement in their Tetris scores after theyÃ¢â‚¬â„¢d Ã¢â‚¬Å“slept onÃ¢â‚¬Â their newfound skill.
In a more traditional experiment, Stickgold has shown that after a snooze, people performed much better on a recently-learned finger-tapping task than after the same amount of time without sleep. Even doubling the amount of time spent learning the task had an insignificant performance benefit compared to simply getting a nightÃ¢â‚¬â„¢s sleep between sessions. He later showed that you donÃ¢â‚¬â„¢t even need a whole nightÃ¢â‚¬â„¢s sleep but that an hourÃ¢â‚¬â„¢s nap can give you the same learning benefits (thank Heavens, I say, from my new vantage-point as a sleep-scavenger).
Stickgold also showed that subjects who werenÃ¢â‚¬â„¢t allowed to sleep soon after learning a new skill never regained the lost benefit, andÃ¢â‚¬â€unless given more practice/sleep cyclesÃ¢â‚¬â€never got quite as good at the skill as those whoÃ¢â‚¬â„¢d been allowed to sleep soon after their training sessions.
More recently, StickgoldÃ¢â‚¬â„¢s lab has shown that sleep makes a stunning difference in the ability of a particular kind of memory known as Ã¢â‚¬Å“declarativeÃ¢â‚¬Â memory to withstand interference. Declarative memory has to do with facts: what you ate for breakfast today, where you last put your keys, what you read in this morningÃ¢â‚¬â„¢s paperÃ¢â‚¬â€all of these are declarative memories. In an elegant experiment, Stickgold taught a group of people a list of word-pairs. Then one half the group was sent off to bed, while the other half was asked to remain awake.
At the end of the waiting period, half the sleepers and half the awake subjects were taught another set of Ã¢â‚¬Å“interferenceÃ¢â‚¬Â words, pairs designed to confuse the memory of the original pairings. Immediately afterward, all subjects were tested on the initial word-pairs. The group that had received the interference teaching but slept beforehand averaged about 76% on the test. The group that received the interference training but had remained awake between the two sessions averaged about 32%.
Apparently, just sleeping on the new information had somehow cemented it into subjectsÃ¢â‚¬â„¢ minds so that it was resistant to interference. To those of us who are desperate to retainÃ¢â‚¬â€accuratelyÃ¢â‚¬â€the new information with which we are bombarded each day, such research is eye-opening, and potentially life-changing.
Stickgold is not the only scientist studying human sleep, of courseÃ¢â‚¬â€there are others working on sleep and cognition (most with results similar to StickgoldÃ¢â‚¬â„¢s), and more researchers providing convincing evidence that sleep boosts your immune system, improves your mood, andÃ¢â‚¬â€oh yeahÃ¢â‚¬â€helps you stay awake when you want to be. There is also evidence that getting poor or insufficient sleep raises your risk of obesity, heart disease and diabetes; increases your blood pressure; and makes you accident-prone: all great reasons to get a good nightÃ¢â‚¬â„¢s sleep (which, according to scientists, is 8–9 hours of uninterrupted slumber). Yet, like many Americans, I am more motivated by the studies showing sleepÃ¢â‚¬â„¢s cognitive benefits. I had been going to go hit the books when I finished this pieceÃ¢â‚¬â€now I think IÃ¢â‚¬â„¢ll just hit the hay. Maybe you should, too.
– Shannon Moffet has an MD from Stanford University School of Medicine, and is in her residency in emergency medicine at Highland Hospital in Oakland, CA. Her book on the brain (and eight dynamic brain-mavens, including Robert Stickgold) is The Three Pound Enigma: The Human Brain and the Quest to Unlock its Mysteries. Moffett recently appeared on The Brain Fitness Program, which aired nationwide on PBS.