A PET scan of the brain of a patient with Alzheimer's Disease
A PET scan of the brain of a patient with Alzheimer's Disease. National Institute of Aging

Using ultrasound waves targeted at the brain, a team of Australian researchers has restored memory to mice with Alzheimer’s disease.

More than 5 million Americans have Alzheimer’s disease, a degenerative condition that causes memory loss, behavioral changes, confusion, and disorientation. Scientists still don’t know what causes it, but they do know some of the factors that might work together to trigger the disease.

Doctors can sometimes tell if someone has Alzheimer’s because of the buildup of a plaque called amyloid-β. Over time, it seems, the brain of an Alzheimer’s patient becomes less efficient at breaking up these clumped-together proteins that can inhibit the communication between brain cells.

Researchers have been trying to find ways to break up the plaque in order to restore memory and speed up slowing brain functions. But they face a challenge because of the blood-brain barrier, a layer of tightly bound cells that separates the blood, water and other chemicals that are inside the brain from those outside it. Though this barrier wears down as a person ages, it’s still extremely difficult to penetrate, so most drugs designed to break up neural plaques don’t even reach the brain. The researchers needed to find a non-invasive way to work through the barrier without causing damage.

Over the course of several weeks, the Australian team sent ultrasound waves–sound waves that move at a much higher frequency than humans can hear–at the mice’s brains. They found that the ultrasound stimulates a particular kind of cell in the brain, called microglia, which work as the brain’s immune system, attacking things that shouldn’t be there. With more of these cells in action, the researchers found that the amount of plaque was dramatically reduced in 75 percent of mice that received the treatment. Analyses over the subsequent weeks showed that the treated mice performed better on memory and spatial recognition tests.

When the ultrasound was combined with an injection of microbubbles, it created a temporary opening in the blood-brain barrier that didn’t impair brain function. While the researchers aren’t sure if that will affect the plaque buildup, it might make it easier to administer pharmaceuticals designed to fight the plaque.

The researchers hope to test their technique on sheep with Alzheimer’s before turning to humans.

Their work was published today in Science Translational Medicine.