https://apnews.com/fdf368a847204e75bafa4bf700546d36

WASHINGTON (AP) — A handful of Alzheimer's patients signed up for a bold experiment: They let scientists beam sound waves into the brain to temporarily jiggle an opening in its protective shield.

The so-called blood-brain barrier prevents germs and other damaging substances from leaching in through the bloodstream — but it can block drugs for Alzheimer's, brain tumors and other neurologic diseases, too.