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According to new research, Alzheimer's disease could be treated by combining light therapy and sound therapy.
The study showed that non-invasive treatments stimulated memory by destroying unwanted proteins in the brains of mice.
The molecules, known as beta-amyloid, cluster into plaques that eat up neurons, causing devastating symptoms of confusion.
Scientists hope that this approach, which works by inducing brain waves known as gamma oscillations, will be equally effective in humans.
Mice with Alzheimer's have remained stable, with no progression of symptoms for some time, after light and sound therapy to stimulate their brain. Human trials are underway
Patients with early Alzheimer's are already enrolled for the first clinical trial of its kind.
Experiments have shown that this increases the ability of genetically modified laboratory animals to develop mental problems similar to those seen in people with dementia.
Visual and auditory therapies have led to improvements when they are applied individually – but the results are even better when they are administered together.
The results, published in the journal Cell, could revolutionize the treatment of dementia.
Dr. Li-Huei Tsai, lead author of the Picower Institute for Learning and Memory at the Massachusetts Institute of Technology, said, "When we combine stimulating visual and auditory stimulation for a week, we find the Commitment of the prefrontal cortex and a very dramatic amyloid reduction.
It lies at the front of the brain and controls the executive function – a set of mental skills that help us get things done. In Alzheimer's, it's one of the first things to do.
The plates were cleaned in large strips of gray matter, including in areas vital for learning and memory.
His team conducted preliminary tests on this type of stimulation in healthy human subjects and showed their safety.
The next step is the clinical trial to determine if the technique provides similar benefits to patients.
Dr. Tsai stated that she was now starting to recruit patients with Alzheimer's disease for double visual and auditory treatment.
Alzheimer's disease causes disruption of brain waves, but the exposure of mice to sound and light treatments has encouraged neurons to trigger normally.
The cells generate electrical signals in several different frequency ranges. Previous studies have suggested that patients with Alzheimer's disease have impaired their gamma-frequency oscillations.
These can range from 25 to 80 hertz, or cycles per second, and are supposed to contribute to mental functions such as attention, perception, and memory.
Three years ago, Dr. Tsai's team discovered the beneficial effects of restoring gamma oscillations in the brain of genetically modified mice in order to develop a form of Alzheimer's disease in rodents.
In this study, researchers used a slight flicker at 40 Hz, 40 times per second, delivered one hour a day.
They found that this reduction in beta-amyloid plaque levels and another tau protein that can cause Alzheimer's disease by developing entanglement.
The treatment has also boosted the activity of immune cells known as microglia that remove unwanted debris from the gray matter.
But these improvements have been limited to the visual cortex. The latest study published in Cell showed that a daily exposure for seven days at a tone of 40 hertz significantly reduced the amount of beta-amyloid in the auditory cortex, which treats sound.
And this had the same effect on the hippocampus, a key memory site located near the auditory cortex.
Amyloid plaque is one of the hallmarks of currently incurable Alzheimer's disease. This sticky accumulation is thought to lead to the progressive destruction of neurons – and dementia.
Dr. Tsai, founding member of the MIT Aging Brain Initiative, said, "We have demonstrated here that we can use a totally different sensory modality to induce gamma oscillations in the brain.
"And secondly, this gamma-induced auditory stimulation can reduce amyloid and tau pathology in the sensory cortex, but also in the hippocampus."
The researchers also showed that after a week of treatment, the mice got much better results when they navigated through a labyrinth, forcing them to remember important landmarks. They were also better at recognizing the objects they had already encountered.
Sound therapy also induced changes not only in microglia, but also in blood vessels, thus facilitating clearance of amyloid.
The researchers then decided to try to combine the visual and auditory stimuli and, to their surprise, found that double therapy had an even greater effect than one or the other.
Amyloid plaques have been reduced in a larger part of the brain, including in the prefrontal cortex, where higher cognitive functions occur. The response of microglia was also much stronger.
Dr. Tsai said, "These microglia are superimposed all around the plates. It's very dramatic.
But if they were treating the mice for a week, then waiting an extra week to perform the tests, many of the positive effects were blurred.
This suggests that treatment should be continually administered to maintain benefits.
In an ongoing study, researchers are currently analyzing how gamma oscillations affect certain types of brain cells, in the hope of discovering the molecular mechanisms underlying the phenomena they observed.
Tsai also hopes to explore why the specific frequency used, 40 hertz, has such a profound impact.
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