Sleep: Spring Cleaning For The Brain?
ScienceDaily (Apr. 11, 2009) — If you've ever been sleep-deprived, you know the feeling that your brain is full of wool.
Now, a study published in the April 3 edition of the journal Science has molecular and structural evidence of that woolly feeling — proteins that build up in the brains of sleep-deprived fruit flies and drop to lower levels in the brains of the well-rested. The proteins are located in the synapses, those specialized parts of neurons that allow brain cells to communicate with other neurons.
Higher levels of these synaptic proteins during waking may be evidence of random experiences that fill the brain every day and need to be dissipated to make room for the learning and memories that are truly significant.
"Much of what we learn in a day, we don't really need to remember," Cirelli says. "If you've used up all the space, you can't learn more before you clean out the junk that is filling up your brain."
Researching are reporting that one purpose of sleep is to clear out synapses. Experiments on flys show that after they've been awake for a while, synapses are larger, and have a higher quantities of proteins associated with those synapses.
In subjects that were well rested, scientists discovered lower levels of proteins and weaker synapses.
In essence, the purpose of sleep is to clean out and reset the nervous system.
My understanding from the article (and parts of it did go over my head (I'm in a large synapse phase right now)) is that throughout the day, the nerves in the brain transmit more and more data. As they do that, the synapses (space between nerve endings) grow and more proteins accumulate. To effectively transmit data then requires more proteins and stronger neuron firing. As this cycle increases, that puts greater stress on the nerves and requires greater physical resources to continue transmitting data.
Though I may be misunderstanding something.
Sleep is therefore biologically necessary in order to promote a properly functioning nervous system. By sleeping and resetting the nerves, the body cleans out a days accumulation of junk.
It's an interesting thought. I would be interested though, in understanding how this process relates to dreaming. It seems that in dreams and deeper levels of sleep, the brain is anything but inactive. With significant internal brain activity, does the nervous system really have time to reboot? Extended sleep without REM or dreaming isn't healthy. It doesn't refresh the body in the long term. Yet, this theory would seem to indicate that lower activity to allow for clearing out the cobwebs is what is called for.
It continues to amaze me that a process that occupies 1/4 to 1/3 of our entire lives is still largely a mystery to us. Between the normal sleep process, sleep disorders, and the entire process of dreaming, there are few concrete answers. Other than, of course, that we generally need it.
More of my musings on Sleep are available here.