Second, not enough sleep, can affect learning because lack of sleep causes brain damage as a result, the brain slowly. That's the lesson does not know the story.
Second, inadequate sleep can affect learning, because lack of sleep can cause brain damage as a result, the brain is slow and therefore do not learn the subject.
Secondly, didn't get enough sleep can affect learning due to lack of sleep cause brain damage as a result, his brain slowly. So, the study doesn't know.