Optogenetics: Lighting the Way for Neuroscience

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The light bulb moment! That instant that you suddenly understand Newton’s third law of motion, when you think of the perfect gift to wow your significant other, or when you have an unexpectedly epiphany about the meaning of life, the universe and everything (it’s 42). It’s almost like your brilliant idea causes a light to switch on in your brain and you feel…illuminated.

But, what if it was the other way around? Rather than your brainwave causing a metaphorical light bulb to appear, what if a flash of light could actually make your brain cells activate? Well, my friends, it can. What I’m talking about here is a relatively new research technique called optogenetics, and it is essentially controlling biological cells with light.

Scientists in many fields have been particularly excited, even giddy, over optogenetics. In 2010, this technique was named Method of the Year by Nature Methods for its “potential to illuminate unexplored avenues of science.” It has even been called “the most revolutionary thing that has happened in neuroscience in the past couple of decades.” So what makes optogenetics so great, you ask? Well, let’s look at an example from neuroscience.

One of the best ways to learn how different pieces of the brain work is to stimulate brain cells (neurons), and see what happens. Stimulating neurons can be tricky, though. One common technique is to use electricity to stimulate the brain. Since neurons are essentially tiny electrical components in the most complex circuit ever (your noggin), electrical stimulation can be used to jump-start a particular area of the brain and observe its effects. A big problem with this approach, though, is that it is not very precise.

If the brain is my laptop and I’m trying to type the letter J, electrical stimulation is something like pounding the keyboard with my fists: FNBJ, HKMJ, HJMH! Sure, I’ve got some J’s in there, but I’ve got a whole lot of other stuff, too. This can make it pretty hard to decipher cause-and-effect in the brain, since you may not know the repercussions of all those M’s, H’s, and K’s around each J. Other research techniques have similar issues, such as using drugs to target certain areas of the brain, which can be imprecise as well as slow-acting.

Optogenetics, on the other hand, allows scientists to switch very specific neurons on and off like a light bulb – in fact, with a light bulb (or, more commonly, with a fiber optic cable). This is made possible by opsins, which are light-sensitive proteins. With genetic engineering, researchers can infect specific neurons with the genes required to manufacture opsins, transforming the target cells into neurons that fire in response to light as well as electricity. Very specific cell types can be targeted by preceding the opsin gene with a specific “promoter gene,” which is only activated in cells that have the appropriate cellular machinery. In this way, many cells can be infected, but only the target cells will end up expressing the opsin gene and becoming sensitive to light.

Using optogenetics, scientists have been able to use light to make heart tissue beat, make skin cells grow in a certain direction, and turn brain circuits off and on in living animals. For instance, one recent study used an implanted fiber optic cable to inhibit the addiction circuits responsible for cocaine-seeking behavior in rats. Other research has focused on using optogenetics to normalize the brain circuits affected by Parkinson’s disease or anxiety disorders. It is easy to see why this technique is an exciting new frontier for research. Maybe someday optogenetics will even illuminate the mystery of enlightenment, and help you spark more “light bulb moments” of your own!

For another great explanation of optogenetics, and some cool demonstrations, watch the video below!

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