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IT TURNS the phrase “light bulb moment” on its head. Stimulating brain cells with light has been shown to improve mental performance in monkeys. The demonstration brings the prospect of using light to treat disease a step closer to reality.
“For the first time, we were able to change behaviour in primates with our technique,” says Wim Vanduffel of Massachusetts General Hospital in Charlestown, who is head of the group that performed the experiment.
Known as optogenetics, the method has the potential to treat conditions such as epilepsy, where light could temporarily deactivate brain cells that cause seizures. It could also treat Parkinson’s disease, activating cells that make dopamine, the chemical vital for controlling mobility that those with Parkinson’s lack.
Previously, it has been used in nematode worms to trigger egg-laying, and in mice to relieve depression and paralysis.
Researchers have also used it in monkeys, but only on single, isolated neurons. Vanduffel and his colleagues wanted to see if they could extend this to entire networks of cells, boosting a monkey’s ability to perform a simple computer-based task.
First, Vanduffel’s team scanned two monkeys’ brains using functional MRI as they located the position of a green dot on a computer screen as fast as possible after being shown a “start” cue. The scans showed the monkeys used the brain’s arcuate sulcus region to do the task.
Next, the team inserted a gene that makes a light-sensitive protein into the cells of the arcuate sulcus. They guided fine, light-conducting needles into the same area through a port attached to the animal’s skull. The protein activated the monkey’s brain cells when it reacted to the light coming through the needles.
The monkeys then repeated the task as light was pumped into their brains. During the treatment, they were able to locate the dot on the screen about 10 per cent faster than before. “One monkey reacted about 20 to 28 milliseconds faster, and the other about 15?milliseconds faster,” says Vanduffel.
Vanduffel says that in unpublished experiments, monkeys undergoing the technique while carrying out a more complex task improved even further. “My hunch is that the harder the task, the more significant the effect,” he says.
“This is just proof of principle, and there’s a very, very long way to go before we can start using it in humans,” he adds.
Although treating humans is a distant prospect for now, the method is evolving fast. Gene switches have been identified that work in specific brain areas, potentially enabling targeted treatment of unhealthy cells.
Arnd Pralle of the State University of New York at Buffalo, who uses magnetism to activate brain cells in worms, describes the work as “exciting”. Activating whole networks of cells for the first time is an important advance, he says.
Tribune Media Service |
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