How are sleep and memory related? 

 

Researchers believe that sleep affects learning and memory.

Lack of sleep lessens a person's ability to focus and learn efficiently about certain matters. That explains why we are easily distracted and quickly agitated.

Sleep is necessary to consolidate a memory (make it stick) so that it can be recalled in the future. Example, when you are reviewing for an exam yet you lack sleep, chances are your brain will have a hard time remembering what you are studying. Most probably, you just stare at your paper and pretend that you are actually doing something but your brain just seems to shut off. It's either you won't recall anything and fail or you better sleep first before actually working on it.