Alzheimer's and Research

A lot is known about the molecules involved in Alzheimer’s disease and the genes that increase its risk, but less is known about how it affects the brain as a system. It was known that in later stages of the disease, when sticky amyloid plaques have already built up in the brain, the brain’s gamma waves lose their strength. Gamma waves ripple across the brain about 40 times per second and appear when the brain is doing attentive work, such as forming memories or solving problems.

Looking for new ideas addressing Alzheimer’s and dementia, MIT formed the Aging Brain Initiative, with an emphasis on interdisciplinary approaches.

Recordings of neural signals in the mice performed by co-first author Annabelle Singer showed weak gamma signals compared to mice without the disease. “The first thing we asked when we saw that was, what happens if you bring gamma back?” says  MIT neuroscientist Li-Huei Tsai, director of the Picower Institute for Learning and Memory and the Picower Professor of Neuroscience.

They stimulated  neurons in the hippocampus, the seat of memory in the brain, to respond to laser light, with light passed through fibers implanted in the brain, testing different rates of flickering. When the light flickered at 40 flashes a second, the stimulated cells responded and induced gamma waves in the brain.

What they found was that gamma oscillations change the behavior of immune cells called microglia, which are responsible for clearing proteins such as amyloid. These cells increase in number with increased gamma strength and become bigger and more active. “This experiment really paid off,” says Tsai.

Ed Boyden’s team used their engineering expertise to fashion a control- lable flickering LED. Tsai’s team studied the effects of the strobe on the visual cortex. “At this point, the project had become very multidisciplinary,” says Tsai.

The intervention not only halved amyloid levels in mice with early stage Alzheimer’s—it also reduced plaques that form in later stages. This finding, which was published along with the team’s other results in Nature in December 2016, makes the intervention potentially relevant for humans. Alzheimer’s symptoms typically do not appear until after plaques have formed. “Most human patients will have plaques in their brains already,” says Tsai.

(from Elizabeth Dougherty writing in Spectrum)

So, maybe light flashing at 40/seconds might be good for you. At other speeds is it bad for you? Are some workplace lights harming us? Are the Notrth Koreans developing flashing lights to make us stupid?