The technology uses light of different frequencies to control the brain.
It’s a brilliant mind-meld of basic neurobiology and engineering that hijacks the mechanism behind how neurons naturally activate-or are silenced-in the brain.
Thanks to optogenetics, in just ten years we’ve been able to artificially incept memories in mice, decipher brain signals that lead to pain, untangle the neural code for addiction, reverse depression, restore rudimentary sight in blinded mice, and overwrite terrible memories with happy ones. Optogenetics is akin to a universal programming language for the brain.
It’s got two serious downfalls: it requires gene therapy, and it needs brain surgery to implant optical fibers into the brain. Rather, the system shines light through the skulls of mice, and it penetrates deep into the brain.
With light pulses, the team was able to change how likely a mouse was to have seizures, or reprogram its brain so it preferred social company.
To be clear: we’re far off from scientists controlling your brain with flashlights. The key to optogenetics is genetic engineering-without it, neurons don’t naturally respond to light. To understand optogenetics, we need to dig a little deeper into how brains work.
A brain cell is like a living storage container with doors-called ion channels-that separate its internal environment from the outside.
Opsins are specialized “Doors” that open under certain frequencies of light pulses, something mammalian brain cells can’t do. Adding opsins into mouse neurons essentially gives them the superpower to respond to light.
In classic optogenetics, scientists implant optical fibers near opsin-dotted neurons to deliver the light stimulation.
Computer-programmed light pulses can then target these newly light-sensitive neurons in a particular region of the brain and control their activity like puppets on a string.
This makes it possible to play with those neural circuits using light, while the rest of the brain hums along.
As you can imagine, mice don’t particularly enjoy being tethered by optical fibers sprouting from their brains. It means that bioengineered neurons, inside a brain, need to have a sensitive and powerful enough opsin “Door” that responds to light-even when light pulses are diffused by the skull and brain tissue.
Because it’s so sensitive, it means that even a spark of light, at its preferred wavelength, can cause it to open its “Doors” and in turn control neural activity.
With ChRmine the team found that a light source, placed right outside the mice’s scalp, was able to reliably spark neural activity in the region.
The next test is whether it’s possible to control a mouse’s behavior using light from outside the brain. Compared to their peers, the light-enhanced mice were far more eager to press a lever to deliver light to their scalps-meaning that the light is stimulating the neurons enough for the mice to feel pleasure and work for it.
As a more complicated test, the team then used light to control a population of brain cells, called serotonergic cells, in the base of the brain, called the brainstem.
In other words, without any open-brain surgery and just a few light beams, the team was able to change a socially ambivalent mouse into a friendship-craving social butterfly. The study suggests that with an injection of a virus carrying the ChRmine gene-either through the eye socket or through veins-it’s potentially possible to control something as integral to a personality as sociability with nothing but light.
Our brains are far larger, which means light scattering through the skull and penetrating sufficiently deep becomes far more complicated.
Again, our brain cells don’t normally respond to light. For unraveling the inner workings of the brain, it’s an amazing leap into the future.
Efforts at cutting the optical cord for optogenetics have come with the knee-capped ability to go deep into the brain, limiting control to only surface brain regions such as the cortex. Other methods overheat sensitive brain tissue and culminate in damage.
Unlike Neuralink and other neural implants, the study suggests it’s possible to control the brain without surgery or implants.