Alzheimer's: How light therapy could protect the brain
Researchers have previously shown that a type of light therapy could potentially reduce toxic proteins that build up in the brain in Alzheimer's disease. Now, the same team has identified what happens at cell level to achieve this result.
In 2016, scientists at Massachusetts Institute of Technology (MIT) in Cambridge found that shining a flickering light into the eyes of mice could reduce the toxic buildup of amyloid and tau proteins that occur in the brain with Alzheimer's disease.
Light therapy boosts a form of brain wave called gamma oscillation, which research suggests is impaired in people with Alzheimer's disease.
More recently, the MIT team revealed that combining light therapy with sound therapy extended the beneficial effects even further.
Those studies also saw that light therapy can improve memory in mice genetically predisposed to develop Alzheimer's disease and spatial memory in older mice without the condition.
The most recent investigation, which now features in the journal Neuron, has shown that boosting gamma oscillations can improve the connection between nerve cells, reduce inflammation, and preserve against cell death in mouse models of Alzheimer's.
It also shows that the treatment's far-reaching effects involve not only nerve cells, or neurons, but also a type of immune cell called microglia.
"It seems," says senior study author Li-Huei Tsai, a professor of neuroscience and director of the Picower Institute for Learning and Memory at MIT, "that neurodegeneration is largely prevented."
Alzheimer's and toxic proteins
Alzheimer's is a condition that gradually destroys brain tissue and associated function through the irreversible loss of cells.
A 2018 report by Alzheimer's Disease International reveals that 50 million people worldwide have dementia, and that for two-thirds of them, Alzheimer's disease is the cause.
Although some treatments can slow Alzheimer's symptoms down for a while, none, as yet, can cure the condition.
In people with Alzheimer's disease, the brain begins to change a long time before they experience symptoms of dementia. Such symptoms include difficulties with thinking and remembering.
Two changes in particular are the development of toxic deposits, or plaques, of beta-amyloid protein between nerve cells, and the formation of toxic tangles of tau protein inside the cells.
Prof. Tsai and her colleagues explain that people with Alzheimer's disease also show another alteration in the brain: "reduced power of oscillations in the gamma frequency band."
powered by Rubicon Project
Scientists have proposed that gamma oscillations are a type of brain wave important for functions such as memory and attention.
In their earlier work, the researchers had shown that exposure to light flickering at a rate of 40 cycles per second, or hertz, stimulated gamma oscillations in the visual cortex of the brain in mice.
Adding sound tones beating at the same frequency enhanced the plaque-reducing effect of the light therapy and extended it beyond the visual cortex into the hippocampus and some of the prefrontal cortex.
Gamma oscillations from both treatments also led to improvements in memory function in mouse models of Alzheimer's disease.
