Courtesy Sidarta Ribeiro
Sleep, to the joy of nappers everywhere, appears to be a building time for memories. Researchers at the Duke University Medical Center successfully recorded the electric signature of individual neurons firing during the two types of sleep, slow-wave sleep and rapid eye movement (REM) sleep.
The team, led by postdoc Sidarta Ribeiro, implanted microscale probes into rat forebrain to determine the firing patterns of individual neurons "resonating" with recently captured memories. The resonations are especially strong during slow-wave sleep and then decrease in force dramatically during REM sleep.1 The same team had formerly shown that neural plasticity genes turn on during REM sleep.2 "It looks like a two-stage process," says Ribeiro. "The memory echoes strongly during slow-wave sleep, which stabilizes it. Then the gene expression machinery turns on during REM sleep to further consolidate it."
Robert Stickgold, a sleep researcher at Beth Israel Deaconess Medical Center and Harvard University in Boston, says he's amazed at the study. "We've known from behavioral studies that you remember more when you have a combination of REM and slow-wave sleep," he says. "Now this research actually shows what's happening on a cellular and molecular level."
- Sam Jaffe