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Your brain will function better after a good siesta, say researchers.
If you are a teacher and catch students napping in your class, fret not. The youngsters may not learn what you teach, but will certainly grasp the next lecture very well. This was the conclusion of some sleep researchers, unveiled at a recent meeting of the American Association for the Advancement of Science in San Diego. Napping during the day not only consolidates memory but also improves the brain. The activity is necessary not just for babies; it’s important for adults and old people too, say researchers.
Matthew Walker of the University of California in Berkeley investigated the effect of long afternoon naps on students’ learning ability. His team found that the more you remain awake during the day, the more the brain loses its ability to learn.
At the University of Arizona, professor of psychology Lynn Nadel and his team investigated the effect of napping on babies, and came to the same conclusion — babies learn to abstract better when they nap.
At the University of Pennsylvania School of Medicine, Marcos Frank found something more fundamental — the brain reorganises itself during sleep, and this reorganisation is essential to learning.
Together, neuroscientists are learning new facets of this seemingly passive activity. The brain does not switch off during sleep. In fact, it remains active, in a different way from when you are awake.
“Sleep is a far more complex activity than we thought,” says Walker. What his research shows now is that the brain has a limited short-term memory capacity, and it needs sleep to free up this space frequently by sending some facts to long-term memory. And it can perform this activity only during sleep. This much is now clear, but things get a bit murky after that.
Walker experimented with 40 volunteers, half of whom took a 90-minute nap in the afternoon. When the two teams learned things at noon and at 6pm, the team that did not nap performed much worse the second time.
“We chose a 90-minute nap to provide for a full sleep cycle,” says Walker. This cycle includes stages of rapid eye movement (REM) and non-REM sleep. REM is a dream state of sleep, and was long thought to be the most important phase of sleep. Non-REM sleep is in three stages — 1, 2 and deep sleep. Memory consolidation occurs during stage 2 non-REM sleep, which during the night constitutes 50 per cent of our sleep cycle.
You enter stage 2 non-REM sleep within 15 minutes of falling asleep, and the brain remains in this state for another 40-50 minutes. So for a nap to really enhance learning, it needs to last an hour.
“We do not know yet whether shorter naps are enough,” says Walker. The scientist also hints at another fascinating aspect of sleep — many older people are known to sleep less, and this could be one reason why they have poorer memories. We would know this in the future, when scientists investigate the mechanisms behind sleep and learning.
At the University of Arizona, Nadel and his team tried to investigate the effect of naps on 15-month-old babies. They created an artificial language, with nonsense sounds but having a close relationship structurally — like subject-verb agreement — with English. Like in the Berkeley experiment, babies in this exercise learned before and after naps. Those who napped were able to translate their previous learning to understand what they learned after the naps. In other words, they were able to generalise their knowledge of sentence structure to understand new phrases better.
What they found was slightly different from the Berkeley team’s finding but was equally important. If babies nap within a specific period after learning a new task, they learned to abstract better.
This kind of learning, the ability to detect patterns in a piece of information, is vital to learning many things in later life. Napping is effective only if it happens within four hours of learning. Babies thus need to nap to understand what they learn during the day.
While these are significant findings, Marcos Frank found something fundamental — the young brain grows more connections during sleep. Frank’s earlier research had indicated that the brain was fundamentally different during sleep from during wakefulness.
This difference is in aspects: electrochemical activity, proteins synthesised and biochemical activity. In early development, during the first five years of one’s life, this reorganisation during sleep becomes critical to its capabilities in later life. “We have some evidence that what happens during early years cannot be acquired in later life,” says Frank.
What this means is clear enough. Babies who are deprived of sleep can develop brains that are deficient. While this may not happen for healthy babies, many who suffer from sleep apnea — a disease where you wake up periodically — can have poorly-developed brains by adulthood.
However, while the research shows how important sleep is for our brains, we still do not know everything about this vital daily exercise. It still remains a puzzle, and hopefully the next few years will throw more light on it.
Source: The Telegraph (Kolkata, India)
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