Stopped brain clock saves memory in hamsters
Broken timekeeper may explain some mental problems
Killing the brain’s clock could sharpen memories. The memory problems plaguing night shift workers, jet-lagged travelers and people with Alzheimer’s disease might be fixed by destroying the body’s timekeeper, a new study in hamsters suggests.
In hamsters with malfunctioning clocks, surgically removing these brain structures reversed the animals’ memory troubles, researchers report in the Nov. 14 Science.
“The result is really quite striking,” says behavioral neuroscientist Ralph Mistlberger of Simon Fraser University in Burnaby, Canada. In these animals, “having a broken clock is worse than having no clock at all,” he says.
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Wedged deep within the brain, two little wing-shaped nuggets of neurons called the suprachiasmatic nucleus serve as a master clock, setting the daily schedule for the entire body. The clock is like an orchestra conductor, says neurobiologist Samer Hattar of Johns Hopkins University. “When the conductor tells the orchestra when to play, the music sounds really good,” he says. But without a conductor to direct the timing, an orchestra can lose its rhythm.
Researchers have known for years that people who lose their daily rhythms — through shift work or travel across time zones — can suffer from memory problems. And recently, scientists have linked memory problems in the elderly to out-of-whack clocks. But why wonky schedules trigger these troubles is unclear, Hattar says.
Studies in animals have been confusing: Removing mice’s master clocks, for instance, disturbs daily rhythms but the animals’ memories remain intact. So Norman Ruby, a behavioral neuroscientist at Stanford University, and colleagues decided to study Siberian hamsters instead.
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Hamsters gave the team more options: Researchers could either cut out the clock completely or leave it there and break it. Just a few well-timed pulses of light at night can confuse the animals’ clocks forever.
Hamsters with busted clocks have memory troubles similar to those of out-of-sync humans — but worse. The animals “are as dumb as a bag of nails,” Ruby says. “They can’t remember anything.”
Old toys seemed new again after just minutes, and mazes became harder to navigate. But when Ruby’s team surgically wiped out hamsters’ broken clocks, the animals’ memory powers snapped back to normal.
Ruby thinks that the broken clocks might pump out chemicals that block memory formation. Working clocks typically send out these chemicals, but only at certain times of day. Cutting out a broken clock could protect the brain from a nonstop flood of memory-blocking chemicals, he says.
If researchers could design drugs that shut down broken clocks in humans, their memories might improve, he says. “If we can help elderly people remember their kids’ faces, and the costs aren’t too great, I’m sure anyone would take that deal,” Ruby says. But he cautions, “We’re in new ground here. We just don’t know what the trade-offs are yet.”
Mistlberger says taking out the master clock in humans “is a pretty wild idea.” And creating clock-targeting drugs wouldn’t be easy. “It’s very, very hard to design a magic bullet that only affects one part of the brain and not others,” he says.