From: unk...@googlegroups.com   
      
   Sleep's Role in Obesity, Schizophrenia, Diabetes...Everything   
   By Gary Stix | December 20, 2013    
      
   The views expressed are those of the author and are not necessarily those of   
   Scientific American.   
      
      
   Is sleep good for everything? Scientists hate giving unqualified answers. But   
   the more sleep researchers look, the more the answer seems to be tending   
   toward a resounding affirmative.   
      
   The slumbering brain plays an essential role in learning and memory, one of   
   the findings that sleep researchers have reinforced repeatedly in recent   
   years. But that's not all. There's a growing recognition that sleep appears to   
   be involved in regulating    
   basic metabolic processes and even in mental health. Robert Stickgold, a   
   leading sleep researcher based at Harvard Medical School, gives a précis here   
   of the current state of sommeil as it relates to memory, schizophrenia,   
   depression, diabetes--and he    
   even explains what naps are good for.   
      
   How far have we come in understanding sleep?   
   Although we understood the function of every other basic drive 2,000 years   
   ago, we are still struggling to figure out what the biological functions of   
   sleep are.  One of the clearest messages now is that for every two hours   
   humans spend awake during the    
   day, the brain needs an hour offline to process the information it takes in   
   and figure out what to save and what to dump and how to file and what it all   
   means.   
      
   So what is sleep for?   
   Memories are processed during sleep. But sleep doesn't have just one function.   
   It's a little bit like listening to tongue researchers arguing about whether   
   the function of the tongue has to do with taste or speech. And you want to   
   say: 'Guys, c'mon, it's    
   both.' There's very good evidence now that sleep, besides helping memory, has   
   a role in immune and endocrine functions. There's a lot of talk about to what   
   extent the obesity epidemic is actually a consequence of too little sleep.   
      
   How did sleep come to play so many diverse roles?   
   It's a little bit of a tricky game because it looks like sleep has been   
   identified evolutionarily as a good time to get stuff done. If you work in a   
   big office, the cleaning staff comes in at night. It's not because that's when   
   they like to or that's    
   when they're most efficient but that's when the people are out of the office   
   and the office is shut down and it's easiest to get housekeeping chores done.   
   I imagine that some functions over evolutionary time have glommed onto sleep   
   because that's when    
   the system is most shut down. Something like two-thirds of your growth hormone   
   is secreted during deep, slow-wave sleep and the presumption is not so much   
   that that this is a critical function of sleep, but that this is the best time   
   to pause and spend    
   energy on growth.   
      
   What is sleep's relationship to memory?   
   Sleep plays a clear and often critical role in the stabilization of memories   
   and in their strengthening and retention, allowing some memories to be   
   retained and others to be let go. It's also critical in the extraction of gist   
   from large collections of    
   information and the discovery of rules that control that information so if you   
   give various stimuli, sleep can help you determine what the rules are as to   
   what the stimuli produce and can even help with the development of insight in   
   patterns and rules    
   that you didn't even know were there.   
      
   What is the importance of dreams?    
   Much less, much less. A decade back we had a paper in The Journal of Cognitive   
   Neuroscience in which we showed that episodic memories of events in our lives   
   aren't replayed in dreams. So the old concept that you dream about what   
   happens, you don't dream    
   what actually happened, is actually well validated. The dreaming brain seems   
   to have as its goal to construct hallucinatory scenarios that bear resemblance   
   to recent events but are different from them.   
      
   Erin Wamsley and I have shown with a computerized maze learning task that if   
   you take a nap after learning you improve on that task more than if you stay   
   awake. Also, if you collect dream reports during that nap, you find it's the   
   people who report that    
   they've been dreaming about the maze task who show the preponderance of   
   improvement during re-testing. Interestingly, if you look at the dream   
   content, it's very clear that the dream content per se is not helpful. It has   
   a sort of wacky bizarre    
   relationship to the task, but not in a way that would help you perform better,   
   which has led us to describe it as a sort of biomarker of a memory process.   
      
   What we think we're seeing is that at the same time that the hippocampal   
   region of the brain, which we know encodes spatial maps, is replaying and   
   strengthening its memory for the layout of the maze, other regions of the   
   brain involved in dreaming are    
   constructing these 'what if' situations, imaginary future scenarios, sort of   
   getting at the question of what is the usefulness of this information.   
      
   One subject reported dreaming of the maze and then remembering being in a bat   
   cave a few years ago, and you can imagine his brain saying: 'OK, how do these   
   two fit together? Is there something about this bat cave that might help me do   
   this task better?    
   Or is there something about this maze task that I should not just file under   
   experiments that I participated in, but file in a way that if I go exploring   
   in a cave again then maybe something I learned about exploring a maze from   
   this game I just played    
   might be useful?' And I think we're getting a sense that that's what   
   dreaming's about--how might this information be useful to me in the future?   
   It's exploring associative networks and trying to find associations that look   
   promising.   
      
   What are implications of sleep for psychiatric disorders?   
   If you take an adult who has both sleep apnea and depression, you'll find that   
   they are very tightly linked. If you have depression, there's a fourfold   
   increase in your likelihood of apnea and if you have apnea, there's a fivefold   
   increase risk of    
   depression. If you take someone with both depression and apnea, and treat the   
   apnea with CPAP [continuous positive airway pressure], you can get their   
   depression scores to drop below clinical levels.   
      
   If you take kids comorbid for sleep apnea and ADHD--in the case of children   
   the apnea is usually caused by enlarged adenoids and tonsils--if you remove   
   the tonsils and adenoids you'll get a larger reduction in the ADHD symptoms   
   than if put them on    
   Ritalin.   
      
      
   [continued in next message]   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)