Clumps of harmful proteins that interfere with brain function were partially eliminated in mice with only light and sound.
MIT-led research has found that strobe lights are used, and a low-pitched tone can be used to restore lost brainwaves in disease, which in turn remove plaque and improve cognitive function in mice that exhibit Alzheimer's-like behavior.
It's a bit like light and sound to trigger their own brainwaves to fight the disease.
This technique has not yet been clinically tested in humans, so it is still too early to get excited. Brainwaves are known to be different in humans and mice.
However, when replicated, these early results suggest a possible cheap and drug-free route to the treatment of the common form of dementia.
How does it work?
A previous study that showed flashes into the eyes of technically-engineered mice 40 times a second treated their version of Alzheimer's disease. The researchers added sound with a similar frequency and found that their results were dramatically improved.
"When we combine visual and auditory stimulation for a week, we see the intervention of the prefrontal cortex and a very drastic reduction in amyloid," says Li-Huei Tsai, one of the researchers at MIT's Picower Institute for Learning and Memory.
It is not the first study to examine the role that sound can play in clearing the brain of the tangles and clumps of tau and amyloid proteins that are at least partially responsible for the disease.
Previous studies have shown that ultrasound thrusts blood vessels so badly that powerful treatments can get into the brain, and encourage microglia, the waste management experts in the nervous system, to increase their tempo.
Several years ago, Tsai discovered that light flickered at a rate of about 40 times per second. This had similar advantages in mice engineered to produce amyloid in the nerve cells of their brain.
"The result was so amazing and so sturdy it took a while for the idea to fall into place, but we knew we needed to find a way to try the same to people," Tsai told Helen Thomson nature back then.
The only problem was that this effect was limited to visual parts of the brain, lacking key areas that contribute to the formation and retrieval of memory.
While the practical applications of the method were somewhat limited, the results suggested how oscillations could help the brain to recover from Alzheimer's disease.
As the neurons of our brain transmit signals, they also generate electromagnetic waves that help keep distant regions in synch – so-called "brainwaves."
Such a set of vibrations is defined as gamma frequencies that travel through the brain at about 30 to 90 waves per second. These brainwaves are most active when we pay close attention and search our memories to understand what is going on.
Tsai's previous study suggested that these gamma waves could be obstructed in people with Alzheimer's and could play a crucial role in the pathology itself.
Light was just one way to make the parts of the brain hum in the gamma tone. Sounds can do that in other areas as well.
Instead of the high-pitched sound of ultrasound, Tsui used a much lower booming noise of only 40 hertz, a sound that was just high enough for humans.
Subjecting mice to just one hour of this monotonous buzzing daily for a week resulted in a significant decrease in amyloid accumulation in the auditory regions, while simultaneously stimulating these microglial cells and blood vessels.
"We have shown here that we can use a completely different sensory modality to induce gamma oscillations in the brain," says Tsai.
As an added bonus, it also helped to cleanse the nearby hippocampus – an important part associated with memory.
The effects were not only evident in the brain chemistry of the subjects. Functionally, mice exposed to treatment have achieved better results in a number of cognitive tasks.
The addition of light therapy from the previous study produced an even more dramatic effect, which erased plaques in a number of areas of the brain, including the prefrontal cortex. These microglia for garbage disposal also went to the city.
"These microglia just pile around the plaques," says Tsai.
Discovering new mechanisms for how nervous systems eliminate waste and synchronize activities is a major advancement in the development of treatments for all types of neurological disorders.
To translate such discoveries into human brains requires more work, especially when there are potential contrasts in how gamma waves occur in mice and human Alzheimer's brains.
Early safety testing has shown that the process obviously has no clear side effects.
This research was published in cell,