WASHINGTON — Epilepsy affects about 2 million people in the United States, and current treatments for the chronic neurological disorder are ineffective for more than a third of cases. But a new technique that uses light to activate brain cells could stop seizures in their tracks, new research suggests.
A team of scientists injected light-sensitive proteins into the neurons of epileptic mice, then shone light on those cells to stop the animals from having seizures.
The new study, presented here Monday (Nov. 17) at the 44th annual meeting of the Society for Neuroscience, hints at a more specific way of targeting these brain storms. [10 Things You Didn't Know About the Brain]
Shedding light on seizures
Known as optogenetics, this method of stimulating the brain using light was developed relatively recently, but it is already being widely used to tinker with brain activity for a variety of applications in mice and other laboratory animals. The technique involves injecting neurons with a virus that contains a gene for a light-sensitive protein found in jellyfish, which makes the neurons fire in response to light.
The main advantage of using optogenetics is its specificity, said Esther Krook-Magnuson, the neuroscientist who led the research while working at the University of California, Irvine. The technique allows scientists to stimulate or suppress neural activity in specific cells and in specific brain areas.
Previous studies have successfully used optogenetic stimulation to stop seizures in animals bred to have different types of seizures. Krook-Magnuson and her colleagues aimed to explore which targeted brain regions may be most effective at stopping seizures in mice.
In this study, the researchers shone light on optogenetically modified neurons while the mice were having seizures. Specifically, the scientists activated cells in the cerebellum, an area at the lower rear of the brain that is involved in controlling body movement. The researchers discovered that the animals' seizures stopped in response to the light therapy.
If activating these cerebellum neurons stopped seizures, the researchers wondered, could suppressing these brain cells actually make seizures worse?
Starting a brain storm
To find out, the scientists shone light on cells that inhibited activity in the cerebellum of seizing mice. Surprisingly, the treatment did not make the seizures worse, but instead stopped them.
The findings suggest that it doesn't matter whether you excite or suppress the activity of these cerebellum neurons to stop a seizure, as long as you disrupt the existing brain activity, Krook-Magnuson said.
The light stimulation has no effect on the average amount of time between seizures, so "it's not just pausing them," Krook-Magnuson said.
Also, stopping a seizure generally didn't have a long-lasting effect on suppressing future seizures, except when the researchers stimulated a region of the brain called the midline cerebellum.
The researchers also did another experiment in which they used light to stimulate part of the hippocampus, a seahorse-shaped brain area known to be involved in memory and spatial navigation and where epileptic seizures often take place.
Cells known as granule cells, found in a structure called the dentate gyrus, are believed to prevent seizure activity in the hippocampus, but scientists don't have a lot of evidence that this happens in live animals.
Krook-Magnuson and her team used light to block the activity of these granule cells in mice that were having seizures, and the seizures stopped. Next, the researchers used light to activate the same cells, and this time, they found it made the seizures much worse. The scientists were even able to induce seizures in healthy (nonepileptic) mice.
The findings of this experiment suggest that granule cells in the hippocampus may be another good target for controlling seizures using optogenetic methods, Krook-Magnuson said.