In a recent research paper published by the Massachusetts Institute of Technology, and featured on the popular NPR podcast “RadioLab,” neuroscientists have shown that subjecting mice suffering from pathology similar to Alzheimer’s disease to oscillating light may reduce the buildup of amyloid plaques that lead to neurodegeneration. The study focuses on gamma oscillations, a pattern of electrical activity between excitatory and inhibitory neurons observed in a healthy brain, and how inducing these oscillations can actually reduce the levels of amyloid plaque buildup in diseased mice engineered to mimic Alzheimer’s disease in humans.
The study confirmed that mice that showed an increase in the concentration of amyloid in the brain also showed deficits in the gamma oscillation patterns observed. This conclusion strengthens previous research, which has shown that gamma oscillations are abnormal in humans suffering from Alzheimer’s disease. When the MIT team induced the gamma oscillations in mice where the pattern was deficient, they found that the exposure decreased the amount of two different isoforms of amyloid plaques (Aβ 1–40 and Aβ 1–42) by 53.22% and 44.62% respectively. In other words, by simply shining a light at the right frequency on specific brain cells, these scientists were able to remove approximately half of the amyloid plaque in these mice.
Furthermore, by performing genome-wide sequencing on the brain tissue of the mice after 1 hour of exposure to 40 Hz oscillations, the MIT researchers found that 35% of the upregulated genes in the tissue were related to the function of the brain’s microglia cells. The genes affected tended to be related to macrophage-stimulating factors and other elements involved in the phagocytosis activities of these neuron-assisting cells. The scientists concluded that the amyloid plaque was reduced due to the enhancement of activity of the brain’s microglia, which become more effective at ridding the brain of the harmful plaques as a result of the “restoration” of gamma oscillations.
These results could mean that a similar method could be engineered to treat humans suffering from Alzheimer’s disease. With that in mind, the scientists showed that they could replicate the results attained in amyloid plaque removal by simply placing diseased mice in an environment with a light flickering at 40Hz, instead of the much more invasive procedure of shining a light at specific neurons in the brain. However, the researchers remain cautious about replicating the results in humans and emphasize that further study is required to determine whether a similar treatment will be therapeutic for humans.
Reference: Iaccarino HF, et al. (2016) Gamma frequency entrainment attenuates amyloid load and modifies microglia. Nature 540, 230-235.