Unique bursts of brain activity during sleep, called sleep spindle, has long been often associated with strengthening recently formed memories. But new research successfully links this surge to specific learning behaviors while awake.
These electrical flurry, which can be observed as sharp spikes on an electroencephalogram (EEG), tend to occur during early sleep stages when brain activity is low.A study published exist Current Biology showed that sleep spindles were prominently present in specific brain regions that were active early in study participants while they were awake and learning assigned tasks. Stronger spindles in these regions were associated with better recall after sleep.
“We can [each] Bernhard Staresina, senior author of the study and a cognitive neuroscientist at the University of Oxford, said. Staresina, Marit Petzka of the University of Birmingham, UK, and their colleagues devised a set of tasks they called a “memory arena” that asked each participant to remember a series of images that appeared within a circle. As the subjects did so, the researchers measured their brain activity with an EEG, which uses electrodes placed on the head. The participants then took a two-hour nap, after which they memorized a new set of images, but then had to recreate the original sequence of images learned before bed.
During the naps, the researchers recorded stronger sleep spindles in specific brain regions that were active during the pre-sleep memory task, and these regions were different for each participant. This suggests that spindle patterns are not “hard-wired” in the default part of the human brain; instead, it is associated with an individual’s thinking patterns. The researchers also observed that participants who experienced stronger sleep spindles in brain regions used in the memory process did a better job of reconstructing image locations after a nap.
Previous research has shown that the spindle triggers changes in the brain that begin the process of strengthening and refining memories, in part by controlling the influx of calcium into certain cells. The new study is the first to directly measure brain activity during learning to support this connection, and it is the first to link better memory recall with stronger spindles in regions that are active during learning, the researchers say—though they note that this does not Does not indicate whether the spindle itself actively improves recall. Future work should examine spindle and other activity in the hippocampus, the brain’s memory center, Staresina said.
The study is “a compelling manuscript supporting a role for the spindle in memory,” said Lourdes DelRosso, a sleep researcher and physician at the University of Washington and Seattle Children’s Hospital who was not involved in the work. She hopes scientists can also study the spindles of people with disorders that affect learning and attention, such as ADHD and dyslexia.