Thursday, October 9, 2008

Circadian Clock May Be Critical For Remembering What You Learn, Researchers Say

Circadian Clock May Be Critical For Remembering What You Learn, Researchers Say: "ScienceDaily (Oct. 9, 2008) — The circadian rhythm that quietly pulses inside us all, guiding our daily cycle from sleep to wakefulness and back to sleep again, may be doing much more than just that simple metronomic task...has shown that having a functioning circadian system is critical to the hamsters' ability to remember what they have learned. Without it, he said, "They can't remember anything."...The change in learning retention appears to hinge on the amount of a neurochemical called GABA, which acts to inhibit brain activity. All mammal brains function according to the balance between neurochemicals that excite the brain and those that calm it. The circadian clock controls the daily cycle of sleep and wakefulness by inhibiting different parts of the brain by releasing GABA...if the hippocampus - the part of the brain where memories are stored - is overly inhibited, then the circuits responsible for memory storage don't function properly..."What I thought was happening was that our animals were having chronically high levels of GABA because they had lost their circadian rhythm," Ruby said. "So instead of rhythmic GABA, it is just constant GABA output."...gave the circadian-deficient hamsters a GABA antagonist called pentylenetetrazole, or PTZ, which blocks GABA from binding to synapses, thereby allowing the synapses to continue firing and keeping the brain in a more excited state. It worked. The learning-impaired hamsters caught up with their intact peers to exhibit the same level of learning retention...Other researchers working with mouse models of Alzheimer's disease have reported similar findings. When those mice were given GABA antagonists, their ability to learn was restored, suggesting a possible link with their circadian system... findings may also have implications for the decline in memory function that older adults in general experience..."

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