We’ve all been there. Your monkey is throwing a fit, jumping on the furniture, screeching like a furry banshee and hurling unmentionable things all over the place. At times like this, wouldn’t it be great if you could just shine a light and control the monkey’s brain? Sorry, that isn’t possible (yet), but researchers have succeeded in stimulating a monkey’s brain with a remarkable level of precision using impulses of light aimed at specific kinds of neural cells. It may not be much help to desperate monkey owners, but it does provide hope of new treatments for sufferers of many neurological disorders.
The July 26, 2012 issue of Current Biology reports that researchers have succeeded in controlling the behavior of monkeys by using pulses of blue light. No, this doesn’t mean that scientists could make the monkeys vacuum the carpet or do the dishes. That’s a long way off. Instead, they were able to use the light pulses to very specifically activate the neurons that control how the monkey’s eyes move.
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That may not seem like much, but this ability to isolate and stimulate particular cells is a major advance in neurology and holds the promise of not only gaining a much better understanding of how the brain works.
The mammalian brain is incredibly complex, but until recently the tools available to the neuroscientist have been absurdly crude. It wasn’t all that long ago that scientists were trying to figure out how the brain worked by cutting out bits of it to see what happened. That’s like trying to learn how a computer works by whacking it with a hammer. Later on, they tried poking brain tissue with needles, shooting electrical currents through it and squirting it with drugs. To keep with our computer analogy, that’s like putting down the hammer in favor of jabbing the CPU chip with a soldering iron.
These methods weren’t just crude, they were slow ... especially given that the brain works at the speed of thought. That’s why in 1979, Nobel laureate Sir Francis Crick suggested using something much finer that could stimulate one specific kind of neural cell instead of everything in the vicinity. He believed that light has that fast, accurate touch. It was replacing the soldering iron with a surgical laser beam.
Since that time, biologists have been trying to find a way to turn Sir Francis’s suggestion into a reality. The result was what is now known as the science of optogenetics and it does a lot more than help you control your monkey’s brain.
Optogenetics is based on a phenomenon that’s fairly common in nature. Many cells have proteins and other chemicals in their membranes that are sensitive to light. The most familiar examples are the rods and cones of the eye that make vision possible, but many organisms are light sensitive for a whole range of purposes. Optogenetics operates by inserting genes from microorganisms relating to this light sensitivity into other cells and using the new sensitivity as a way of providing very specific stimulation to the cells to produce very specific results at a speed close to that of neural tissue. Again keeping with our computer, the optogeneticist now has a way of studying the microchip circuit by circuit.
Previously, scientists have managed to gain similar light-stimulated control on simpler animals, such as invertebrates and rodents, but the monkeys are a major achievement.
"We are the first to show that optogenetics can alter the behavior of monkeys," says Wim Vanduffel of Massachusetts General Hospital and KU Leuven Medical School. "This opens the door to use of optogenetics at a large scale in primate research and to start developing optogenetic-based therapies for humans."
According to the researchers, this ability to stimulate the brain and observe changes offers hope to sufferers of Parkinson's disease, addiction, depression, obsessive-compulsive disorder and other neurological conditions.
"Several neurological disorders can be attributed to the malfunctioning of specific cell types in very specific brain regions," Vanduffel says. "As already suggested by one of the leading researchers in optogenetics, Karl Deisseroth from Stanford University, it is important to identify the underlying neuronal circuits and the precise nature of the aberrations that lead to the neurological disorders and potentially to manipulate those malfunctioning circuits with high precision to restore them. The beauty of optogenetics is that, unlike any other method, one can affect the activity of very specific cell types, leaving others untouched."
Source: Current Biology