In 2005, Stanford scientist Karl Deisseroth discovered how to switch individual brain cells on and off by using light in a technique he dubbed 'optogenetics'.
Research teams around the world have since used this technique to study brain cells, heart cells, stem cells and others regulated by electrical signals.
However, light-sensitive proteins were efficient at switching cells on but proved less effective at turning them off.
Now, after almost a decade of research, scientists have been able to shut down the neurons as well as activate them.
Mr Deisseroth’s team has now re-engineered its light-sensitive proteins to switch cells much more adequately than before. His findings are presented in the journal Science.
Thomas Insel, director of the National Institute of Mental Health, which funded the study, said this improved “off” switch will help researchers to better understand the brain circuits involved in behavior, thinking and emotion.
In the upper left opsin, the red color shows negative charges spanning the opsin that facilitated the flow of positive (stimulatory) ions through the channel into neurons. In the newly engineered channels (lower right), those negative charges have been changed to positive (blue), allowing the negatively charged inhibitory chloride ions to flow through. “This is something we and others in the field have sought for a very long time,” Mr Deisseroth, a senior author of the paper and professor of bioengineering and of psychiatry and behavioural sciences said.
“We’re excited about this increased light sensitivity of inhibition in part because we think it will greatly enhance work in large-brained organisms like rats and primates."
The new techniques rely on changing 10 of the amino acids in the optogenetic protein.
“It creates a powerful tool that allows neuroscientists to apply a brake in any specific circuit with millisecond precision, beyond the power of any existing technology,” Mr Insel explained.
This technique could help scientists develop treatments for patients with some brain diseases as it could allow problematic parts of the brain to be switched off with light and tackled with minimal intrusion.
Merab Kokaia, PhD, a professor at Lund University Hospital in Sweden who has used optogenetics to study epilepsy and other conditions praised the research.
"These features could be much more useful for behavioral studies in animals but could also become an effective treatment alternative for neurological conditions where drugs do not work, such as some cases of severe epilepsy and other hyper-excitability disorders," he said.