How a strange flickering light therapy may help battle Alzheimer’s
Since2016, a team of MIT neuroscientists has been exploring the strangehypothesis that external exposure to a light flickering at 40Hz can improve cognitive function and reverse the neurodegenerationassociated with Alzheimer's disease. A new study has now homed in onexactly how, on a cellular level, this light treatment could beworking.
Li-Huei Tsai and colleagues at MIT's Picower Institute forLearning and Memory first discovered in 2016 that amyloid and tauproteins seemed to be eliminated from mouse brains following exposureto a flickering light. Further work revealed adding a 40 Hz auditorytone to the process improved the efficacy of this treatment, however,it was not known exactly how this external stimuli was actuallyinfluencing the brain.
The new study set out to uncover exactly how a flickering lightcould stifle cognitive decline, using two unique mouse modelsengineered to overproduced the toxic proteins that contribute toneurodegeneration. The animals were exposed to light flickering at 40 Hzfor one hour every day for between three and six weeks.
Incredibly, the mice engineered to overproduce tau proteinsdisplayed no neuronal degeneration after three weeks of treatmentcompared to a control group that displayed nearly 20 percent totalneuronal loss. The other mouse model, engineered to produce aneurodegenerative protein called p25, displayed no neurodegenerationwhatsoever during the entire six weeks of treatment.
"I have been working with p25 protein for over 20 years, and Iknow this is a very neurotoxic protein," explains Tsai. "We foundthat the p25 transgene expression levels are exactly the same intreated and untreated mice, but there is no neurodegeneration in thetreated mice. I haven't seen anything like that. It's veryshocking."
The researchers then zoomed in on the light-treated animal'sneurons and microglia to study whether the treatment induced anyunusual changes in gene expression. The light-treated mice revealedincreased neuronal expression of genes associated with synapticfunction and DNA repair. In microglia, the brain's immune cells,there was a decrease in genes associated with inflammation.
All of this suggests that the flickering light treatment seems toinduce brain activity that both enhances the ability of microglia tofight off inflammation and enables neurons to better protect andrepair against damaging toxic proteins. Of course, these hypotheses stillonly offer a partial answer to the question of how this strangetreatment is working.
The researchers now know what may be occurring in the brain tocause these beneficial results but, still, no one knows exactly how a40 Hz flickering light can trigger these specific changes to gene expression deep in the brain. Further work in animal models isunderway to better understand this unusual mechanism, while human trialstesting the sound and light treatment in Alzheimer's patients havealready begun.
The new study was published in the journal Neuron.