Sound Stimulation May Help Clear Alzheimer’s Plaques

The study, published in the journal PNAS, is the first to experimentally confirm in primates that 40-Hz stimulation can be considered as a non-invasive physical approach to treating Alzheimer’s disease. In addition, the scientists found important differences between the results obtained in primates and those previously documented in rodent experiments, which are widely used in the preclinical stage.

The team worked with nine elderly rhesus monkeys (Macaca mulatta), ranging in age from 26 to 31 years. The animals naturally developed extensive amyloid plaques in their brains, similar to the β-amyloid changes seen in human Alzheimer’s disease. Because of these similarities, these primates are considered a promising model for evaluating new therapeutic methods before moving to clinical trials.

In a randomized controlled experiment, animals in the experimental group received one hour of auditory stimulation daily at 40 Hz using a 1 kHz pure tone for seven days. At the end of the course of therapy, the level of Aβ42 and Aβ40 in the cerebrospinal fluid increased by 205.61% and 201.00%, respectively, and the differences compared to the initial values ​​were statistically significant. These data are consistent with previous results in mice and support the hypothesis that 40 Hz stimulation promotes the transfer of β-amyloid from brain tissue into the cerebrospinal fluid, which is considered to be an indicator of enhanced clearance.

Notably, when reassessed 35 days after completion of stimulation, elevated CSF Aβ concentrations persisted and did not decrease significantly from levels immediately after treatment. Such a long-lasting effect has not previously been observed in experiments on rodents. This consistent result strengthens the case for the use of 40-Hz stimulation as a promising non-invasive approach for the treatment of Alzheimer’s disease and highlights the importance of aged rhesus monkeys in translational research for the disease.