Staggered lessons may work better

Training at irregular intervals improves learning in sea snails

Sea snails learn more effectively on an oddly timed series of training sessions rather than regularly spaced lessons, a new study finds. If the results extend to humans, they might suggest ways of improving students’ study habits.

The work, published online December 25 in Nature Neuroscience, shows how a deep knowledge of biology and powerful computer models can lead to insights about the brain, says neuroscientist Eric Kandel of Columbia University, who won a Nobel prize in 2000 for his work on sea snail memory.

When the rat-sized Aplysia californica receives an unpleasant shock, it retracts its gill and an appendage called a siphon. After numerous shocks, it will become sensitized, learning to retract the siphon and keep it in for a while.

Scientists normally expose sea snails to the signal at regular intervals over several hours to sensitize the animals. But Jack Byrne of the University of Texas Medical School at Houston and colleagues wondered whether there was a better way. “There’s no real logic for why people use one protocol over another, other than it works,” he says.

Kandel and others have worked out a lot of the biochemical details of how sea snails learn and form memories. When the creatures start to learn something, two major molecular cascades kick off in nerve cells. Genes jump into action, churning out proteins that then spur other genes into action. One of these cascades happens quickly, and the other one is sluggish, but both need to deliver their products at the same time for a memory to stick.

Byrne and his team used this knowledge to make a mathematical model of how best to deliver this biochemical double-hit. The team asked the computer how to spread out five shocks over a period of several hours. Instead of evenly spacing the five at 20-minute intervals, the model suggested a completely different pattern: Give three doses 10 minutes apart, followed by a fourth dose five minutes later, wait a half hour, and then give a final dose.

“You have these irregular intervals between the treatments,” Byrne says. “That’s the very nonintuitive part of it that you couldn’t have predicted.”

When Byrne and his team tried this training protocol, it worked better than the standard 20-minutes-apart training doses. With the standard protocol, the sea snails forgot what they’d learned after five days. But on the enhanced protocol, the sea snails remembered five days later.

“The model spat out exactly what turned out to be right,” says neuroscientist Lila Davachi of New York University. “It’s just beautiful.”

The team hasn’t tested the snails past five days, nor tried doing the enhanced protocol on multiple days to see how far memory can be extended.

Laura Sanders

Laura Sanders is the neuroscience writer. She holds a Ph.D. in molecular biology from the University of Southern California.

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