The Power of Brain Waves
By Sonia Chen
Alzheimer’s is an extremely common disease, with over 3 million cases in the United States alone. Though aging increases a person’s risk of having Alzheimer’s, old age does not directly cause the disease. As Alzheimer’s progresses, the symptoms of dementia, which is memory loss, worsen, and there is currently no way to halt or reverse the damage. However, researchers may be getting closer to a cure for Alzheimer’s by using optogenetics, a technique that involves flashing lights at specific speeds, to activate brain cells that have been loaded with light-sensitive proteins on mice.2
In the brain, each neuron sends electrical impulses down its length and relays this signal to adjacent brain cells. On a larger scale, these electrical activities can create cycles in the brain known as neural oscillations, or brain waves. These brain waves are categorized by their rate, or how many times the neurons creating the waves fire in a single second. The slowest waves, delta waves, are created when neurons fire up to only four times per second, which usually happens during sleep. Beta waves are created when neurons fire up to thirty times per second. The fastest waves, gamma waves, are created when the neurons fire up to 90 times per second.2 Each of these different types of brain waves propagate during different periods of brain activity: delta waves during periods of deep sleep, beta waves during periods of wakefulness, and gamma waves during periods of attentiveness, memory formation, and perception.2 In people with Alzheimer’s, the gamma waves in the brain show much less activity than in normal individuals, explaining the characteristic memory loss experienced by Alzheimer’s patients.1
Normally, cells called microglia are found in the body’s central nervous system: the brain and the spinal cord. Microglia are the central nervous system’s main immune defenders, engulfing and destroying unwanted cells and materials such as extra proteins in the brain. One signature characteristic of Alzheimer’s is the formation of clusters made up of beta-amyloid protein. This “plaque” forms in the synapses between neurons, preventing proper communication of electrical signals between brain cells and causing the brains of Alzheimer’s patients to gradually lose certain functions.2 In unaffected brains, gamma waves that result from mental processes can bolster the activity of microglia, allowing them to clear out the plaques, and prevent the development of Alzheimer’s.2 When Alzheimer’s develops, the gamma waves are no longer regular and frequent, lessening the activation of microglia and allowing the buildup of harmful plaques. Using this knowledge, scientists have developed a possible optogenetic treatment for Alzheimer’s that uses flashing lights to activate neurons in the brain and induce the formation of gamma waves.
How does optogenetics use flashing lights to stimulate the brain? First, neurons are treated with a special light-sensitive protein that comes from algae; this protein is an ion channel that positions itself in the cell membrane of the neuron. The ion channel proteins open in response to blue light, allowing charged ions to flow across the membrane and create a current that is nearly identical to that which occurs in normal neurons. Newly-activated neurons can then go on to create gamma waves, stimulate microglia, and destroy beta-amyloid plaques. So far, this treatment has only been tested on mice, but the results show great potential.2 When the researchers flashed a light with a frequency of 40 Hz at brains of mice with Alzheimer’s-like symptoms, gamma waves were generated, microglia were activated, and about half of the beta-amyloid plaques were removed (Iaccarino 74). Not only were the Alzheimer’s-causing plaques removed, but the ability for mice to memorize and learn new skills was improved. While these findings could translate to cognitive improvements for human Alzheimer’s patients in the future, optogenetics is extremely invasive and may not ever be used in humans in its current form.2 Nevertheless, a less invasive way of stimulating gamma oscillations has been explored. As it turns out, visual stimulation alone can actually start gamma oscillations in the primary visual cortex.1 Simply having the mice look at a flickering light resulted in a significant reduction of beta-amyloid protein. Though this method must be strictly controlled in the lab, researchers may be able to develop a reliable treatment for Alzheimer’s from this method in the near future.
Alzheimer’s disease affects an immense portion of the world’s population. As the baby boomers move into the age group that has the highest risk of developing Alzheimer’s (anyone older than 65), the development of treatment methods that could potentially prevent, halt, and reverse the disease is becoming increasingly important for the well-being of most of the human population, both now and later in life.
- Iaccarino, Hannah F., et al. “Gamma Frequency Entrainment Attenuates Amyloid Load and Modifies Microglia.” Nature, vol. 540, no. 7632, 2016, pp. 230-35, www.nature.com/nature/journal/v540/n7632/full/nature20587.html. Accessed 31 June 2017.
- Yong, Ed. “Beating Alzheimer’s With Brain Waves.” The Atlantic, 7 Dec. 2016, www.theatlantic.com/science/archive/2016/12/beating-alzheimers-with-brain-waves/509846/. Accessed 30 June 2017.