Researchers at the Washington National Biomedical Research Center have developed a long-sought technological “toolbox” that allows scientists to control and monitor brain activity with light in non-human primates for years at a time, a breakthrough expected to bridge the gap between basic laboratory research and life-saving human medicine.
The study, published in Nature Communications, introduces a new platform for optogenetics, a technique that involves genetically modifying specific neurons to make them sensitive to light. By shining light on these modified cells, scientists can effectively flip a “switch” to turn neural circuits on or off. While the technology has existed for two decades, its application in monkeys has been notoriously difficult to sustain.
“The challenge with the brain is that it is an extraordinarily complex network composed of billions of neurons.,” said Dr. Azadeh Yazdan, the study’s lead researcher. “If you’re studying the heart, you can hold it in your hand, dissect it, and understand how it works because it is largely a mechanical organ. The brain, in contrast, is fundamentally electrical, composed of billions of neurons communicating through dynamic patterns of activity. This complex exchange of electrical signals is much more difficult to observe and understand.”.
According to Dr. Yazdan, her team’s advancement serves as a vital “unlock” for the global scientific community. “A lot of monkey researchers say we are not doing optogenetics, or we’re scared of doing it because it’s hard,” she noted. ” What we claim in this paper is that, by using the toolbox we have developed, it becomes possible to conduct long-term experiments and study these circuits in a more sustained and systematic manner”.
The platform’s stability is a major milestone. The lab has successfully maintained functional brain interfaces in monkeys for over four years. This longevity is crucial for studying the progression of chronic conditions like Alzheimer’s disease, stroke, and mental health disorders.
Dr. Yazdan’s research involving non-human primates is an important pathway to future therapies.
“Macaques share a lot of anatomy and physiology with us,” she explained. “For example, we have highly dexterous movement, the ability to use our hands and fingers for tasks like turning a key in a lock or using a spoon to feed ourselves. This capability arises from a unique organization of the motor cortex and its connections to the spinal cord, a feature shared only between these animals and humans..”
Because of this biological proximity, the ethical treatment and care of the animals are paramount to the lab’s mission. Dr. Yazdan’s “NERD Lab,” short for Neural Engineering and Rehabilitation Design, gave of the primary monkeys in the study the names, “Hydrogen” and “Lithium,” who have been with the lab for nearly eight years.
“Providing the highest standard of care is essential, as these animals play a critical role in advancing our understanding of the brain,” Yazdan said. “We are committed to maximizing the knowledge gained from each study while minimizing the number of animals involved. We also actively advocate for approaches that allow us to continue working with the same animals over time, when appropriate, to reduce the need for additional subjects. Maintaining that continuity is important to both the science and the welfare of the animals.” By demonstrating the long-term safety of the technology, her team was able to work with scientific reviewers to show that continued monitoring, rather than euthanasia (which is sometimes required in such studies) was appropriate in this case. The combination of long-term stability and accessibility of this toolbox to the scientific community also has the potential to reduce the number of animals required in future studies.
This paper is part of a larger cluster of technological advancements from Dr. Yazdan’s team. She alluded to two other significant studies that the lab has been developing for multimodal interfacing with the brain featuring the “Smart Dura” which was developed in collaboration with the lab of Maysam Chamanzar at Carnegie Mellon University. Smart Dura is an advanced interface that enables researchers to image the brain’s surface physiology and anatomy while simultaneously recording electrical activity through micron-scale, semi-transparent electrodes. It also allows for targeted stimulation of underlying neural circuits using both optical and electrical stimulation. This technology was featured in a paper published earlier this year in Microsystems & Nanoengineering and its versatility was demonstrated in a second paper published in Advanced Science.
The ultimate goal of this integrated technology is to move toward practical therapies. Dr. Yazdan noted that her lab is already seeing promise in using stimulation to accelerate recovery from stroke and to help clear the pathologies associated with Alzheimer’s disease. By making this platform accessible to other labs, the team hopes to accelerate the journey toward a future where the most complex diseases of the human brain finally have a cure.