optogenetics and brain control

June 24, 2009

Blue light causes the cells to become activated, sending out electrical signals. Yellow light causes the cells to become inactive, blocking any signal propogation though it. (credit: h+ Magazine)

Blue light causes the cells to become activated, sending out electrical signals. Yellow light causes the cells to become inactive, blocking any signal propagation though it. (credit: h+ Magazine)

Implanting electrodes in someone’s brain and then shocking them seems somewhat sci-fi to most people, but it’s a medical reality. We’ve found that by electrically stimulating parts of the brain and vagus nerve, we can reduce the effects of epileptic seizures, Parkinsons’, and other disorders.

This whole process sounds incredibly complicated, and it is, but from a larger perspective, it’s quite simplistic. Basically, we just stick wires in peoples’ heads and shock them and see if their symptoms decrease. A slight divergence from this external electrical stimulation is the subfield of optogenetics, coined first by Karl Deisseroth at Stanford. I read a nice summary of his recent work in h+ Magazine and will give you the thumbnail sketch.

Instead of sticking an electrode down into your brain, Deisseroth’s group stuck a fiber optic cable that can deliver different wavelengths of yellow and blue light. Normal neurons are not light sensitive, but the targets of this optical stimulation are genetically modified to be so. Deisseroth’s group squirts in a bit of genetically engineered virus exactly in the brain where they want to stimulate. This virus has two genes culled from algae and archaeon that then reprogram the surrounding neurons to be sensitive to blue and yellow light.

These neurons now become inhibited, unable to produce an electrical signal, when subjected to the yellow light and excited, producing an electrical signal, when subjected to the blue light.

This process, while a good bit more involved than brain stimulation, achieves basically the same thing: getting neurons to fire when we want them to. But it also has then benefit of allowing us to directly block neurons from firing, which we could only somewhat achieve through electrical stimulation by shocking one part of the brain and hoping that it causes another part to go quiet in the way we want. Silencing areas of the brain directing could prove an incredible boon in getting the brain to behave in the way that we want.

I see this optogenetic technology as an additional tool, not necessarily a replacement, to electrical brain stimulation. As our understanding of how the neurons in specific parts of the brain are connected and our technology for controlling those neurons improve, our ability to mediate the many debilitating diseases and conditions that plague us will improve dramatically.

Some of you may be uncomfortable with the idea of messing around “under the hood” of the most complicated machine in the world, but I’d then ask you how direct stimulation (or inhibition) is really any different than the many drugs that target the brain. This technology is simply the next step in our ability to fine tune ourselves.

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