Sentence Completion

Complete the sentence with ONE word from the passage for each blank.

Sleep does more than rest the body; it also helps the brain clean itself. During deep sleep, the spaces between brain cells widen, allowing fluid to flow through more freely. This fluid washes away waste proteins that build up while we are awake. Researchers think that interrupting this nightly process over many years may be linked to the gradual decline seen in some memory disorders.

During deep sleep, fluid flows through widened spaces in the brain and washes away waste , a process that may help protect .