From Science News article Staggered lessons may work better :
"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."