Could a sound, emitted at a specific frequency, offer a solution to Alzheimer's disease?
Researchers have demonstrated that 40 Hz auditory stimulation, administered to elderly monkeys, causes a notable increase in markers linked to the clearance of amyloid proteins, and thus of the plaques of the same name, in the cerebrospinal fluid. This observation paves the way for non-invasive therapies, potentially applicable to a disease that affects millions of people.
Conducted by a team from the Kunming Institute of Zoology in China, the study focused on rhesus macaques aged 26 to 31 years. These animals naturally develop cerebral amyloid plaques, similar to those found in human patients. After one hour of daily 40 Hz sound stimulation for seven days, scientists observed a dramatic increase in Aβ protein levels in their cerebrospinal fluid, indicating a brain cleaning dynamic.
Unlike the frequently used mouse models, these primates offer a closer parallel to human pathology. Their brains indeed exhibit extensive amyloid deposits, making the data particularly interesting for future clinical applications.
At the end of the treatment period, concentrations of Aβ42 and Aβ40 surged by more than 200% in the cerebrospinal fluid. Notably, these levels remained high for more than five weeks after the stimulation stopped, a prolonged effect not previously documented in rodents. This persistence suggests the technique could induce lasting clearance of harmful proteins.
Compared to current treatments, such as monoclonal antibodies which can slow disease progression but come with risks of side effects, 40 Hz auditory stimulation presents itself as a simple, low-cost, and non-invasive intervention. It thus represents an attractive option for complementary or alternative approaches.
40 Hz auditory stimulation caused a significant increase in amyloid proteins in the monkeys' cerebrospinal fluid, an effect that persisted for over 5 weeks.
Credit: KIZ
These results, published in
PNAS, provide strong experimental evidence to continue exploring this method. They motivate future research aimed at adapting the technique for humans, with the goal of designing accessible and safe treatments for age-related cognitive disorders.
The Principle of 40 Hz Stimulation
40 Hz stimulation refers to the application of a sound at a frequency of 40 cycles per second, which corresponds to brain gamma waves. These waves are linked to cognitive functions like attention and memory. By exposing the brain to this frequency, it is possible to influence its electrical activity and potentially synchronize neurons.
This synchronization could thus improve communication between nerve cells and facilitate processes like the clearance of metabolic waste. Work on animal models has, for example, indicated that 40 Hz stimulation can increase the activity of glial cells, which are involved in brain cleaning and specifically in the removal of amyloid proteins.
Simple and low-risk, this approach uses common sensory stimuli, such as pure tones, which can be easily administered. It therefore opens the prospect of at-home therapies or complementary to standard care, without the need for heavy equipment. Ongoing research seeks to determine the ideal parameters, such as duration or intensity, to optimize the benefits.