The importance of sleep

An excerpt of ‘The brain that changes itself’ struck me as particularly explanatory of why proper sleep is so important to recover from visual brain damage. It also explains why not getting the amount of sleep needed or interruptions of my sleep don’t just feel like a bad day but as a step closer to the abyss. So sleep certainly isn’t death’s cousin, not sleeping properly is…

Scores of studies show that sleep helps us consolidate learning and memory and effects plastic change. When we learn a skill during the day, we will be better at it the next day if we have a good night’s sleep. “Sleeping on a problem” often does make sense.

A team led by Marcos Frank has also shown that sleep enhances neuroplasticity during the critical period when most plastic change takes place. Recall that Hubel and Wiesel blocked one eye of a kitten in the critical period and showed that the brain map for the blocked eye was taken over by the good eye — a case of use it or lose it. Frank’s team did the same experiment with two groups of kittens, one group that it deprived of sleep, and another group that got a full amount of it. They found that the more sleep the kittens got, the greater the plastic change in their brain map.

The dream state also facilitates plastic change. Sleep is divided into two stages, and most of our dreaming occurs during one of them, called rapid-eye-movement sleep, or REM sleep. Infants spend many more hours in REM sleep than adults, and it is during infancy that neuroplastic change occurs most rapidly. In fact, REM sleep is required for the plastic development of the brain in infancy.

A team led by Gerald Marks did a study similar to Frank’s that looked at the effects of REM sleep on kittens and on their brain structure. Marks found that in kittens deprived of REM sleep, the neurons in their visual cortex were actually smaller, so REM sleep seems necessary for neurons to grow normally. REM sleep has also been shown to be particularly important for enhancing our ability to retain emotional memories and for allowing the hippocampus to turn short-term memories of the day before into long-term ones (i.e., it helps make memories more permanent, leading to structural change in the brain).