Too many connections? Sleep makes room for new memories

http://www.sciencenews.org/view/generic/id/38692/title/Sleep_makes_room_for_memories

"In a study in rats, Cirelli and her colleagues discovered that a molecule that works with the brain chemical glutamate becomes more and more abundant the longer rats are awake. The molecule, the glutamate receptor GluR1, helps forge connections, called synapses, between neurons. When rats are awake, the amount of GluR1 in the brain may climb up to 40 percent higher than levels found when the animal has been asleep for a few hours.

A new study in fruit flies showed that all areas of the brain have much higher levels of molecules found at synapses. Normally, strengthening a synapse is a good thing. It is one of the steps thought to be important in memory formation. But brains can’t continue to build up existing connections forever, Cirelli says.

“We cannot afford to keep growing our synapses one day after another, because very soon they would become unsustainable,” she says. “Stronger synapses come at a very high price.”

It takes a lot of energy, cellular supplies and other resources to maintain the connections. And if a neuron puts all of its energy into continually strengthening old synapses, it will never form new ones, making it impossible to learn new things."

REALLY INTERESTING... so, there is an upper limit to learning and remembering, or so Cirelli's theory postulates/depends on. It kinda makes sense in the way that there is a limited amount of resources. But are resources really that scare that too many synapse would become unsustainable? I'm not so sure... It is kinda a cool idea to think that sleep will clear out old/unused/unsustainable synapses though... transfer to and from the working memory sort of thing as well I would assume.

"Poe and her colleagues found that REM sleep turns off the brain chemicals norepinephrine and serotonin, both used for stabilizing synapses. Injecting serotonin into the brains of rats during sleep disrupted the rats’ ability to form certain kinds of memories, suggesting that the ability to remove old connections during sleep is important for making new memories."