I recently picked up Hallucinations,
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Nov 122012
Mar 052011
Later this weekend I’ll continue the science/spirituality/religion thread, but for now I just wanted to note an interesting finding about sleep. This article from Science News Daily uses the lovely phrase “sleep fragility” to describe the unlovely phenomenon of sleep that is vulnerable to disruption.
Researchers examined subtle changes in the brain’s alpha rhythm and found that these changes are a good indicator of times when sleep is more likely to be interrupted by noises or other stimuli from the outside world. Alpha waves appear in electroencephalograms (EEGs) or magnetoencephalograms (MEGs) and are typically associated with wakeful relaxation. However, they also occur during sleep, although they aren’t visible to the eye in an EEG but must be revealed by mathematical analysis. In the study described in Science News Daily, sleeping volunteers were exposed to typical background sounds that can interrupt sleep; the sounds were repeated at increasing volume until their sleep was disrupted, as indicated by their EEGs. When alpha wave activity was stronger, their sleep was disturbed by quieter sounds. In other words, the alpha wave activity was correlated with more fragile sleep.
Sometimes I’m apt to drift up to the surface of sleep; it feels just like that, like something in my mind is too light and restless to stay submerged, and I keep floating to the surface. It’s not a whole lot of fun, but I like knowing a little more about what electrical activity is likely to be going on in my brain when it happens. (I wish I knew why, though!) And the researchers who have done this work say that it could be the first step toward finding ways to apply sleeping medications or other treatments that would kick in only when sleep is most fragile, rather than knocking the brain out entirely for the whole night. (I like the word “sledgehammer” that one of the scientists uses to describe sleeping pills; that’s one reason I’m generally reluctant to use them, because I don’t like to sedate my brain to that degree.)
Sleep deprivation and emotions
Brain and mind
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Oct 222007
When I was younger, I could bounce back more easily from sleep deprivation; now that I’m in my mid-40s, it’s harder to deal with a short night or worse yet, a series of short nights. My mind becomes muddy and my body feels sluggish. Studies have investigated the physical and cognitive effects of sleep deprivation, but not as much has been done to examine the emotional effects of sleep loss. A recent study looked at 26 healthy volunteers, some of whom kept a normal sleep/wake schedule and some of whom had to stay awake for 35 hours. Then, while their brains were scanned with fMRI, both groups were exposed to images that started out bland and became increasingly emotionally disturbing. The sleep-deprived group showed much more activity in areas of the brain involved in processing emotions (the press release doesn’t say specifically which areas) compared to the group who slept normally. The press release also doesn’t say if the people were monitored in any other way for the strength of the emotion they were feeling (self-reporting, respiration or heart rate, etc.). (I’d be particularly interested in correlations with what people reported they were feeling.) At this point there’s no telling why this should be the case or how sleep might buffer the effects of emotional stimuli, but this is an interesting start. This press release from EurekAlert has more information.
Sleep does more than consolidate memories
Psychology
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Feb 252007
It’s been known for awhile that when we sleep, we process our memories in a way that makes them stronger and better established. Some new research indicates that in addition, we’re better able to see the connections between things we have learned if we have a chance to sleep on it, and to generalize rules and overall themes. This short article from New Scientist gives some more info.
Take a nap
Human origins and evolution
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Oct 312006
One of the worst things about having a day job is that it’s impossible to take a nap when mid-afternoon drowsiness hits. I have to admit that even on the weekend when I’m at home, I tend to drive myself to keep going even when I long to lie down and close my eyes for a few minutes, but maybe it’s time to reconsider. This article from the Toronto Star by Kurt Kleiner discusses the pleasures of the nap and gives some justification for the practice. He cites a couple of studies that show that napping improves cognitive performance, and also points out that our circadian rhythms seem geared toward an afternoon nap. I’ll have to remember one of this guy’s closing lines next time I want to take a nap: “When I nap, I accept my own nature, and the nature of the universe that made me.” That works for me.
How the brain wakes up
Brain and mind, Psychology
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Aug 192006
I’m always interested in the ways people use computer metaphors to describe their brains. Maybe it’s just because my job centers on IT, but it seems like I hear a lot of people wishing their brains could have a faster processor or a RAM upgrade. My favorite was when someone pointed out that being able to shut our processors off when it’s time to sleep would be a blessing. This press release talks about the other end of the day: what happens when the brain picks up the threads of consciousness in the morning when we wake up, or as the headline says, how it boots up. Some recent research shows that nitric oxide plays a role in the process by enhancing the communication that goes on between the thalamus and the cortex. The thalamus is something of a filter that receives sensory input and passes it along for further processing (or not, depending on the input). The cortex receives a bit of the incoming information (the proverbial sip from a firehose) and builds up a picture of what’s going on, which it then passes back to the thalamus. The thalamus then passes along whatever information is needed to fill in or make sense of the picture. In an animal study, nitric oxide (which is released in the brain when we are awake and aware) strengthened the signal coming back from the cortex to the thalamus. So maybe nitric oxide that’s released into the brain as we wake up helps the brain come to grips with the sensory data coming in from the outside world before it starts in on the more complex task of navigating through the day. Thanks to Mark for pointing out this story.
Jan 162006
When you have to learn a new spatial task, your hippocampus generates new neurons that help anchor your memory of what you’ve learned. In sleep-restricted rats, this process appears to be derailed. In a recent study, rats who had less sleep were worse at remembering a path through a maze than their well-rested counterparts; also, the rested rats showed increased neurogenesis in their hippocampi, but in the sleep-restricted rats, the rate of survival for these newly created cells was lower. These rats weren’t deprived of sleep altogether, just given less sleep than is normal for them, so the experiments more or less mimic what a lot of humans live with. On the other hand, the sleep-restricted rats did better than the rested rats when the task involved relying on sensory cues rather than memory for navigating the maze, indicating that since they couldn’t use memory, they were forced to find another strategy that was not as affected by the lack of sleep. So it looks like interfering with sleep might rearrange the normal hierarchy of processes the brain uses. Interesting stuff for those curious about what is going on in the brain during sleep and why the brain needs sleep (a fact that busier hominids sometimes regret). At least we’re not lab rats swimming through a maze. Thanks to Greg H. for telling me about this story.
http://www.brightsurf.com/news/headlines/view.article.php?ArticleID=22476
Chief nourisher in life’s feast
Thought and consciousness
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Jan 082006
Here’s an article about sleep. Specifically, it discusses two competing ideas about sleep: a) that sleeping is so universal and so costly to an organism that it must have arisen early in the history of life and serve some absolutely vital purpose, and b) that it varies so much between different types of creatures that it might be the result of convergent evolution, the same basic solution being applied in response to different problems. Either way, there are some interesting facts here; I didn’t know that rats can live longer without food than they can without sleep, for example. What I wish I understood is how you can feel like you’re barely staying awake (as I feel right now) and then be suddenly, discouragingly alert when your head hits the pillow. As with the debate about whether sleep solves a single universal problem or serves different functions in different creatures, I suspect this question awaits further research.