Sleep and Learning
Common sense holds a well-rested person can learn more easily and more thoroughly than a sleepy person. Let’s look at the science.
Rested brains learn more readily. Well-rested (not sleep- deprived) brains do a bunch of tasks better than sleepy brains. In tests of response time to stimuli, agility, ability to remember new material and to perform things like mental arithmetic, the superiority of the rested brain has been shown again and again. It’s so cliché that these types of tests are performed by psychology students early in their training in order to get their feet wet with research.
A more interesting finding is how sleep after learning something helps cement the learning. During sleep the brain turns recently acquired memories into long term memories. Sleep helps lock in the learning. This appears to be one of the main biological functions of sleep.
EEG readings of stage 2 sleep show short bursts that sleep scientists have named Spindles (because of how they look on the EEG record.) Each Spindle lasts about a second, and there may be as many as a thousand in each person’s brain every night. Spindle events are not understood by neuroscientists. It is suspected they have something to do with the transfer of memory from the hippocampus to the frontal cortex and the formation of long-term memories. Sleep spindle activity is associated with the integration of new memories with existing knowledge. The number of spindle events, and deep sleep, declines in old age, which is thought to correspond to overall decline in mental acuity in older people.
The light sleep of stages 1 and 2 have been shown to be important in helping the brain being plastic to learning new material. This also points to an explanation for why a 90-minute nap in the day can help people remember material they just learned. And why "sleeping on it" often helps people mentally digest their situation.
In a normal night's sleep, the majority of the stage 1 and 2 sleep happens in the second half of the night. If you cut your sleep short, you may not learn as much as you could from the previous day's events. Although it has long been known that a period of sleep assists in solving problems, new research found that the effect is greater for difficult problems than for easy problems.
Skeptics point out that people with high intelligence quotients or good at school do not necessarily sleep more than others.
Harvard University article: Sleep clears the mind: How sleep prepares the brain for new learning
Memory formation and abstract concepts
Sleep is particularly important in learning higher-order abstract concepts. Research has found a significant correlation between the level of improvement in tests of learning and the amount of slow-wave sleep obtained. People consolidate the new learning much better after a period of sleep than during a waking day. Even an afternoon nap helps. More on sleep and memory.
Slow wave (deep) sleep promotes episodic declarative memory consolidation. This is the more important type of memory for schoolwork, in contrast with procedural memory which is important for physical actions. Daytime naps are paticularly useful for consolidating new procedural memories. Indeed, electroencephalogram tests of nappers find the more spindle events produced, the better the napper is equipped to learn.
The decline in the amount of time spent in slow wave sleep among old people may explain why older people have a harder time learning new things that younger people. It is indeed hard to teach an old dog new tricks, partly because the dog’s sleep patterns have changed.
Sleep disorders in people with learning disabilities
People with intellectual disabilities get sleep disorders at the same rate as the general population and doctors treat disorders in the same way. Here's an abstract of academic Sleep studies of adults with severe or profound mental retardation and epilepsy
The main difference is that treatment with cognitive behavioral therapy (CBT) may be more difficult, or not feasible. A low percentage of insomniacs are actually treated with CBT anyway.
Here is a good article:
Sleep Disorders in Persons with Mental Retardation - A Significant Factor in Many Behavioral/ Psychiatric Problems? http://www.thenadd.org/cgi-bin/checkmember.pl?page=pages/membership/bulletins/v1n5a2
Sleep and Traumatic Memories
Psychologists have changed their tune in recent years, and explicitly don't debrief people after traumatic events, for fear of reinforcing the memories. Another bit of psychological first aid is to not let people go to sleep after a traumatic event. If they sleep, the relive the event in their dreams and consolidate into long-term memory. PTSD can be thought of in some way as an over-consolidation of memory. Dreaming causes the person to live the incident over again and again.
Post-traumatic stress disorder. Psychologists have found they can reduce the severity of post-traumatic stress disorder by restricting sleep in people right after they experience the trauma. The idea is that sleep would enable the person who has suffered the trauma to dream about it, relive it, and to transfer the images of the trauma from the short-term memory to the long-term memory. Sleep restriction may not eliminate PTSD, but it can lessen its effects.
"O Sleep, rest of all things, mildest of the gods, balm of the soul..."
(Iris to Hypnos. Ovid, Metamorphoses)