Several news outlets reported yesterday that strobe lights could become a future non-invasive treatment for Alzheimer’s disease. By exposing mice to a flickering light, researchers were able to reduce amyloid – the protein that forms clumps in the brains of people the disease.
The story is based on new research published in the journal Nature that investigated the role of a specific pattern of brain activity – called gamma waves – in the development of Alzheimer’s. The researchers used sophisticated techniques to enhance gamma waves in mice that were genetically altered to develop Alzheimer’s and found that they could reduce the build-up of amyloid protein.
This might sound like the stuff of science fiction, but it is a great example of the innovative approaches that researchers are taking to better understand the causes of dementia and explore alternative ideas for treatments.
Using flickering light in this way is not a likely treatment approach for people with Alzheimer’s, but the principle of boosting gamma waves is something that could now be explored further.
What is a gamma wave?
A gamma wave (also called a gamma oscillation) is specific pattern of electrical activity that occurs in the brain when several neurons are activated at the same time. For the wave of activity to be a gamma wave, it has an average frequency of 40 Hertz or 40 oscillations per second. The role of gamma waves is not well understood but it has been suggested that they are fundamental to our ability to make sense of the world around us.
Previous research has suggested that gamma waves are reduced in people with Alzheimer’s disease. This was assumed to be a result of the damage that occurs to brain cells as the disease progresses. However, the experiments conducted in this new study suggest that reduced gamma waves could play a role in causing the disease.
What did the researchers do?
In the first part of this study, the researchers used a technique called optogenetics to trigger gamma waves in the hippocampus – the memory centre of the brain. They did this by genetically engineering mice to have a light-activated ion channel added to a particular type of brain cell known as fast-spiking interneurons. The researchers then used light pulses to activate the interneurons at the right frequency to create gamma waves.
When they created gamma waves in mice who were genetically altered to develop Alzheimer’s disease, they found that they could reduce the production of amyloid protein in the brain. Amyloid protein is found in all healthy brains, but in Alzheimer’s disease it gets damaged and builds up in toxic clumps. By triggering gamma waves for one hour, the researchers were able to reduce the amount of amyloid present in the hippocampus by about 50%.
The researchers performed a range of experiments to understand how gamma waves work to reduce amyloid in the brain. They found that they work in two ways: they reduce the production of amyloid protein in the first place, and they also activate microglia cells to clear away the damaged protein. Microglia are specialised immune cells that clear away toxic debris in the brain and are increasingly implicated in the development of Alzheimer’s disease.
Taken together, their experiments show that gamma waves are reduced early in mice that will develop Alzheimer’s disease. When gamma waves are artificially boosted in the memory centre of the brain, the build-up of amyloid protein is reduced. In theory this could delay or prevent the onset of dementia symptoms, although the researchers did not directly test the mice for changes in memory.
Could ‘flickering lights’ be developed as an Alzheimer’s treatment?
Optogenetics is a very useful tool in neuroscience research for investigating the roles of different brain cells and circuits. However, because it involves inserting a foreign gene into the DNA of brain cells, it is not feasible to consider as a treatment approach in people.
The researchers tried to get round this barrier in the second part of the study by testing an alternative method for inducing gamma waves in the brain. They exposed mice to a light that flickered 40 times per second and found they could induce gamma waves in the part of the brain the processes visual information. As before, they found that this ‘flickering light’ treatment was able to activate microglia to clear away damaged proteins and reduce amyloid levels by about 50%.
This exciting finding suggests that it could be possible to induce gamma waves in people with something as simple as patterns of light. However, this technique only induced gamma waves in the visual centre of the brain in mice, not in other brain areas. The challenge now would be to find ways to induce gamma waves in the parts of the brain that are affected in Alzheimer’s disease in a non-invasive way.
What gamma waves do in Alzheimer’s disease and what causes them to be disrupted in the first place is not clear, but this study highlights that it is an important area for further research.
These interesting experiments show there are ways to boost gamma waves in mice, but we do not know whether the findings would be replicated in people. If we could find a way to induce gamma waves in the right brain areas in people with Alzheimer’s, we do not know whether this would have any beneficial effects on the progression of dementia symptoms.
Image used under the Wikimedia Commons license.