How simple sound and light are treating Alzheimer’s Disease

In 1906, a German psychiatrist and neuroanatomist performed an autopsy on the brain of a patient who displayed abnormal symptoms while alive. Over the course of several years, this woman’s behavior, as well as her speech and language, became erratic. She forgot who people were, became paranoid, and, as her condition worsened, suffered total memory loss. When her doctor dissected her brain, he found unusual plaques and neurofibrillary tangles in her cerebral cortex. He quickly alerted his colleagues of this “peculiar severe disease.” The doctor was Alois Alzheimer.

More than a century later, the medical community is still trying to understand Alzheimer’s disease (AD), a neurodegenerative brain disorder. But early studies have demonstrated that we may be able to mitigate some of the damage created by AD simply by exposing people to certain waves of sound and light.

This research is part of the growing discipline of neuroaesthetics, or the study of how the arts and aesthetic experiences measurably change the body, brain, and behavior—and how this knowledge is translated into specific practices that advance health and well-being. It’s a topic we explore in depth in our new book, Your Brain on Art.

We are learning how these sensory experiences alter a complex physiological network of interconnected systems including neural, psychological, immune and endocrine, circulatory, respiratory, and higher-order brain systems like the cognitive, affective, reward, and motor systems.

Over the past 20 years advances in technology have enabled us to get inside your heads and to study the extraordinary ways the arts impact us. Turns out that research is now proving what artists have always known.

The unique challenges of Alzheimer’s disease

With AD in particular, the mechanisms for how the disease progresses are complex and hard to pin down. We do know that less than 1% of people with AD have a specific genetic mutation that causes the disease. Rather, lifestyle and environmental factors are believed to be major determinants.

What Dr. Alzheimer originally saw in that autopsied brain were deposits of amyloid beta protein, now known as amyloid plaques, as well as interwoven bundles of fibers known as tau tangles. These are thought to be two of the primary biomarkers of AD, but many yet-to-be-identified factors are also believed to be involved. Damage from AD usually begins in parts of the brain related to memory, such as the hippocampus. 

As it progresses, AD can affect the cerebral cortex, leading to deterioration of language, reasoning, and social behavior. This is all a medical way of saying that this disease attacks us at the very heart of what makes us human, slowly destroying brain activity and taking our memories, our relationships, and our independence along with it.

AD is now the most common form of dementia in adults, and the sixth leading cause of death overall. Recent assessments of people over 65 suggest that AD may actually be the third-leading cause of death. You will not find more passionate people than those who seek a cure for AD, and yet this disease has been stumping modern medicine for decades. While we are learning more and more about the role of the accumulation of plaques and tangles in our brain, the current treatments for the disease are all still focused on ameliorating the symptoms and trying to slow the progression.

If we know that aesthetic inputs affect us on a cellular level—sound can actually sync the beating of heart cells—might targeted aesthetic treatments help with something as complex as AD?

Why certain frequencies blast amyloid plaques

This is a question that has motivated Li-Huei Tsai, a neuroscientist and the director of the Picower Institute for Learning and Memory in the Department of Brain and Cognitive Sciences at the Massachusetts Institute of Technology. Li-Huei has spent the past three decades working to understand and treat neurodegenerative diseases, in particular AD.

“It has not turned out to be a disease attributable to just one runaway protein or just one gene,” Li- Huei explained in a 2021 op-ed in The Boston Globe. “In fact, although Alzheimer’s is referred to as a single name, we in the Alzheimer’s research community don’t yet know how many different types of Alzheimer’s there may be, and, therefore, how many different treatments might ultimately prove necessary across the population.”

AD researchers have traditionally pursued small-molecule pharmaceuticals and immunotherapies that target a single errant protein, the amyloid. But Li-Huei believes Alzheimer’s to be a broader systemic breakdown, and she has thought about more encompassing, and hopefully effective, treatments. For several years now, her lab has pursued novel approaches using the aesthetic interventions of light and sound. We know the influence that light and sound have on the human body. People suffering from seasonal affective disorder benefit from light therapy. Blue light before bed stimulates our brain and disrupts sleep. Sound vibrations change our physiology. But how might this work on a brain experiencing AD?

Our neurons generate electrical signals to communicate at several different frequencies, and these form oscillations, or brain waves. These are measured in cycles per second, or hertz, and there are five types of brain waves that are read on an EEG: delta, theta, alpha, beta, and gamma. Delta, the slowest of our brain waves, occur when we’re asleep. Theta waves happen when we’re extremely relaxed and are awake, but are in a dreamlike state. Alpha waves happen when our brain is, in effect, idling; we’re relaxed, but ready to respond if necessary. Beta waves happen when we are alert and paying attention. And gamma waves are the fastest, most subtle of the brain oscillations and are associated with our perception and consciousness.

Researchers have observed something notable in mice who have been genetically modified to have AD for the purposes of research. They have disruptions to their gamma oscillations when they are performing a task such as running through a maze.

It’s believed that gamma oscillations, which range from 25 to 80 Hz, play a role not only in conscious cognition but also in memory formation. There’s evidence that gamma rhythms are important for hippocampal memory processing. It follows, then, that a brain disorder like AD, which impairs memory, might include disturbances in gamma wave rhythms. Li-Huei had a theory: Would introducing gamma oscillations from another source—light and sound—help to resynchronize neurons and reduce Alzheimer’s pathology?

Li-Huei turned to optogenetics, a form of noninvasive sensory stimulation, to encourage groups of brain neurons to move and, hopefully, synchronize their firing patterns again. It was a curious first-year student in Li-Huei’s graduate program who then suggested researching gamma oscillations at 40 Hz. Gamma waves at 40 Hz have already been shown to affect human brain waves, significantly increasing the overall brain oscillation. Current research suggests that exposure to a light or sound at 40 Hz promotes gamma brain-wave activity through brain-wave synchronization.

In 2016, the lab developed a device that produced 40 Hz of gamma waves through a flickering light device. Mice with AD were exposed to the light for one hour a day. State-of-the-art technology, such as magnetoencephalography (MEG), electroencephalography (EEG), and fMRI were used to investigate and visualize brain oscillation changes. After just one hour of light, “we saw profound reduction of amyloid peptides,” Li-Huei says.

The reductions were primarily in the visual cortex of the brain, so Li-Huei and her team wondered if adding in sound would allow the treatment to reach other areas of the brain. They exposed mice to one hour of sound tones that were set at 40 Hz. This happened for seven consecutive days. One week of this sound therapy dramatically reduced the amount of beta amyloid in the auditory cortex, the area of the brain associated with processing sound, as well as the hippocampus, which is located nearby. After one week of this treatment, the mice had also vastly improved cognition and were able to better navigate a maze.

With sound and light together, there were even greater results. As Li-Huei recounted her findings to us, we were astonished. “When we combine visual and auditory stimulation for a week, we see the engagement of the prefrontal cortex and a very dramatic reduction of amyloid,” Li-Huei explains. There was also a reduction in tau tangles, and the synaptic density that had been compromised by AD increased along with neuronal density.

Sound and light seemed to be erasing AD pathology and improving cognition.

It’s hard to believe, but that doesn’t make the results any less promising

“Some people have said to me that this is too good to be true. How can anything be so effective and also be so simple?” Li-Huei says. “I know it might sound like a fairy-tale kind of story, but that’s what we’re seeing.”

Now that she knows light and sound work, the next step is determining exactly why that is. There have been numerous theories, but currently Li-Huei believes that increased gamma oscillations in the brain engage many different systems and cell types. Because of this, the gamma waves may help with amyloid removal, for instance, through various brain waste-clearance mechanisms. The light and sound treatments stimulated the activity of cells known as microglia, which are debris-clearing immune cells that influence brain development. The treatment not only spurred changes in microglia but also in the blood vessels, “possibly facilitating the clearance of amyloid,” she told us. 

There’s a fluid that fills the cavity in our brain called cerebrospinal fluid (CSF). The CSF can enter the brain tissue and travel along the blood vessels. The CSF then will mix with the interstitial fluid of the brain. “So, if you have any kind of a waste substance in the brain, outside the cell, the CSF can flush it out and clear it through the lymphatic system,” Li-Huei says. “We found that increased gamma oscillations actually promote the CSF entering into the brain and promote this kind of waste-clearance mechanism.”

The combined visual and auditory treatment has now been tested in healthy human volunteers to assess its efficacy and safety, and the researchers are beginning to enroll patients with early-stage Alzheimer’s for a study.

And Li-Huei is now translating the breakthrough science in her lab into therapeutic devices. One device is composed of a 2-by-2-foot light box containing hundreds of white LED bulbs and a sound bar capable of delivering sound clicks at 40 Hz. A person can sit in front of it about 6 feet away and use it for about an hour a day. Early studies of the effects of this aesthetic intervention have found that using light and sound in this way induced those gamma oscillations in the brain, maintained functional connectivity in several brain networks, and slowed brain atrophy. Just as sound waves move heart cells, light and sound are changing brain oscillations to support healing.

This passage was adapted from the book Your Brain on Art by Susan Magsamen and Ivy Ross. Copyright © 2023 by Susan Magsamen and Ivy Ross. Reprinted by arrangement with Random House, a division of Penguin Random House LLC. All rights reserved.