The other way to add genetic material is by infecting an animal with a virus that reprograms certain cells. This approach has been used in people, Hillman says, but carries enough risk that most optogenetic experiments in humans are probably still a long way off.Another challenge for optogenetics, Hillman says,German machine tool sector expects decent 2014
has to do with delivering light to cells deep in the brain. "It's really hard to get light to go deep," she says, "and we all know this just from trying to shine a flashlight through our hand."Researchers are also finding that in some optogenetic experiments, light is reaching too many cells in the brain, says Hillel Adesnik from the University of California, Berkeley, who also spoke at the Optical Society meeting. "It's like slamming the thing with a hammer," Adesnik says.
So scientists are looking for ways to deliver light with less force and more precision. "One thing that's been very much discussed," Adesnik says, "is how we can control the cells one at a time, or 10 at a time, or 1,000 at a time — but extremely specifically."Despite these challenges, researchers see huge potential for optogenetics. Already, they say, the techniques are changing our understanding of disorders such as epilepsy.Scientists have known for a long time that epileptic seizures occur when brain cells start firing out of control. But they've been struggling to understand the role of brain cells called inhibitory neurons, which can reduce firing in other cells, Adesnik says.
"Prior to optogenetics, there was no way to control these neurons and test hypotheses," Adesnik says. Now, he says, scientists have shown that by altering that activity of inhibitory neurons in mice, it's possible to start and stop epileptic seizures.The finding suggests that some day it may be possible to halt a person's epileptic seizure with a flash of light, Adesnik says. And by tweaking other networks in the brain, he says, doctors may be able to help people with Parkinson's disease, depression, or even schizophrenia.That's because most neurons don't normally respond to light. So you have to add genetic material to every brain cell you want to control. Scientists can do that in mice with genetic engineering, but that's not an option for people.