"These are people who haven't been able to speak in connected sentences for weeks or months who suddenly start having a conversation, speaking in full sentences, understanding and replying," Hamblin told Seeker. "People who had to be fed by caregivers can suddenly pick up a knife and fork and start eating their own meals. Remarkable changes."
Equally remarkable were the changes that occurred after the light treatments were stopped. The cognitive and behavioral benefits reversed almost immediately. The study called for a four-week period in which light treatments were suspended, but one patient's symptoms returned with such force that his family begged for the device back.
Scientists like Hamblin believe that PBM works by stimulating the mitochondria within cells to produce more ATP, the energy that powers cellular activity.
"The mechanisms are manifold," Hamblin explained. "Clearly you're boosting metabolism - ATP, oxygen consumption, brain energy. You're improving cerebral blood flow. But you're also stimulating the formation of new brain cells and the formation of new connections between existing brain cells. And together, these two processes comprise neuroplasticity, basically the brain's ability to reorganize itself, to repair itself."
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Margaret Naeser, a research professor of neurology at the Boston University School of Medicine, studies the use of PBM headsets and helmets to treat patients with traumatic brain injuries, stroke, and military veterans suffering from Gulf War Syndrome - an unexplained illness seen among those who fought in the 1991 Gulf War that can involve dizziness, insomnia, fatigue, and headaches, among other symptoms.
Naeser is in the middle of a $2.8 million study for the U.S. Department of Veterans Affairs to improve cognition and memory in vets using LED treatments. She explained that red light at 600 nm wavelengths and near-infrared light at 810 nm or 830 nm is absorbed by an enzyme inside cellular mitochondria called cytochrome c oxidase (CCO). In patients with brain injuries or disorders, the receptors on the CCO enzymes become clogged with nitric oxide.
"When you deliver near-infrared photons to that brain cell, the nitric oxide is pushed outside the cell wall, and that promotes increased blood flow, which is what you want in an area that's damaged," said Naeser. "And that's what we see on our MRI images, the increase in blood flow targeted to where we put the photons. I couldn't believe it. I was shocked."
In addition to priming blood flow in the brain, light treatments seem to boost the brain's autoimmune response to amyloid beta, the proteins that form the crippling plaque deposits found in Alzheimer's. In a healthy brain, immune cells called microglia are tasked with clearing out excess amyloid beta. In an Alzheimer's brain, microglia undergo a dangerous transformation. They not only stop attacking amyloid beta, but secrete a toxin that damages healthy brain cells.
In the MIT study, repeated exposure to blue light pulsing at the gamma frequency (40 Hz) appeared to train the Alzheimer's brain to return to its normal rhythm. In turn, it caused the microglia to return to their healthy state and start clearing out amyloid beta debris.
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Naeser explained that PBM light treatments use a different pathway to fight amyloid beta - sleep.
"You and I are building up amyloid beta all day," said Naeser. "When you go to sleep at night, the cerebrospinal fluid comes in and massages the cells in the brain to pull out amyloid beta buildup, get it into the blood vessels and wash it away."
Dementia patients sleep terribly, which disables the body's natural ability to clear out amyloid beta. Naeser noted that red and near-infrared light increase melatonin levels, and that caregivers of dementia patients receiving PBM treatments reported that the therapy greatly improved their sleeping habits.