What's more, the researchers identified an associated brain wave pattern that appears to be the factor that determines whether an image was subsequently forgotten or retained. This second pattern occurs in the brain's hippocampus, a region that is important for memory retention.
This is important, the researchers say, because it suggests that the brain retains certain memories even when we cannot consciously recall them. “The forgotten images do not simply disappear from the brain,” said researcher Hui Zhang in a statement.
The discovery could help develop new therapies for those with memory problems.
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Meanwhile, a second sleep study from U.S. researchers has uncovered what may be the brain’s primary “sleep switch.” The study identifies a batch of nerve cells called the ventrolateral preoptic nucleus (VLPO) that appear to function as the on-off button for falling asleep.
Working with genetically engineered mice, researchers at Beth Israel Deaconess Medical Center in Boston used both chemical and optical techniques to stimulate the VLPO brain cells. In both cases, triggering the cells caused the mice to fall asleep. The results confirmed earlier findings that the VLPO cells are active during sleep and that damage to them causes insomnia.
“Our paper is the first test of what happens when you activate the VLPO neurons,” said Clifford Saper, chairman of the Department of Neurology at Beth Israel Deaconess Medical Center. “The findings support our original observation that the VLPO cells are essential to normal sleep.”
The research could help in the future development of drugs and therapies to help those with insomnia and other sleep disorders.
One last interesting note: While the researchers were monkeying around with the “sleep switch” cells, they discovered that continued activation of these neurons caused the body temperatures of the mice to drop as much as six degrees Celsius. This phenomenon may be associated with the deep sleep and lowered body temperatures of animals that hibernate during the winter.