Almost a decade ago, Stanford University researchers jump-started a new field of study when they genetically altered brain cells, shone light on them, and demonstrated that they could control the modified neurons. This brain-control technique, called optogenetics, has since taken off at labs around the world and could lead to breakthroughs for Parkinson’s disease, addiction, depression, and spinal-cord injuries.
But optogenetics uses complicated processes that require the separate delivery of genes, light, and electricity to a tiny part of an animal brain. Now researchers in Germany and Switzerland have found a way to simplify the procedure by building a flexible implantable device that delivers all three things. The researchers recently reported their results in the journal Lab on a Chip.
In optogenetics, scientists insert genes for light-sensitive proteins found in algae into mammalian nerve cells. The genetically modified neurons then begin to produce those proteins. Shining light of one color on the neurons causes the proteins to open certain channels in the cell membrane, letting in sodium ions that activate the neuron. Light of another color causes an influx of chloride ions, turning the neuron off. This provides precise control and is a leap forward from electrical stimulation, which is usually used to trigger a response in the brain. While electrical stimulation excites all the nerve cells around a relatively large electrode, light can trigger the specific neurons that took up the new genes and can switch them on and off in milliseconds, the timescale at which neurons fire.