Decode the Mind - Optogenetics: Is Mind Control Actually Possible?

Once imagined only by the most speculative science-fiction writers, the idea of ‘mind control’ using technology has been around in popular culture at least since the beginnings of the Cold War, where paranoia surrounding control of people by governments was at an all-time high. The mainstream view was that controlling people’s actions and thoughts was much too far-fetched to become a reality in the near future. This perception, though, may be starting to change as scientists in recent years have made pioneering advances into fields such as optogenetics, a technique which allows precise control of how neurons fire by using flashes of light from a laser – all very space-age!

As cool or as concerning as that might sound to you, the reality is that, for obvious ethical reasons, this technology is unlikely to make its way to human brains. Instead, it has been developed for use in animal models or cultures of cells in a dish. Scientists use these models in neuroscientific research to approximate the human nervous system, but at a simpler level, and hopefully learn more about human health and disease from these studies. Because it’s very rarely possible to use living human brains for research, and the human brain is also enormously complex, a great deal can be learned from studying simpler systems. There are many techniques available to record the activity of certain neurons, such as making them fluoresce when they fire, or attaching a micro-electrode to record their electrical activity, but until the early 2000s we couldn’t make specific groups of neurons fire on command. This meant that we could only record how neurons behaved in a certain condition, or use a very crude method to ‘switch on’ all the neurons in a relatively large area with an electric shock. However, this was not specific enough to answer many important questions about how different types of neurons function and interact. Optogenetics provides a way to selectively activate a group of similar neurons which all express a particular gene. This is useful as it gives us the opportunity to examine a manageable number of neurons, while still getting enough information to tell us something useful about how the brain might work.

So how does optogenetics actually work?

Neurons are not normally responsive to light, so they need to be modified to fire in response to this new signal, and this modification should only be applied to a small group of cells which express similar genes, so that we can work out the specific role of these cells. Most commonly, this is achieved by injecting a virus into a culture of cells or an animal brain. This virus has been modified to cause the cells it infects to produce an ion channel called channelrhodopsin, similar to the light-sensitive proteins found in your eye. This channel becomes incorporated into the cell membrane, and opens in the presence of light of a certain wavelength, allowing positively charged ions into the cell and causing the neuron to fire an electrical signal, or ‘action potential.’ Importantly, the modified virus also contains other proteins that make it specific to a certain type of neuron, so the channelrhodopsin will only be present in the membranes of cells of that type. The reason light is such a good trigger is that neurons fire on a timescale in the milliseconds, and while similar techniques are available to activate particular cells with drugs (called chemogenetics), only light can be switched on and off fast enough to control the neurons precisely.

So we have a way to control a small set of neurons very specifically and effectively, but what can this actually tell us? Thousands of experiments from hundreds of labs since the technique’s invention in 2005 have investigated the role of different small populations of cells in the brain. We now know much more about the circuits involved both in basic processes like sensation and movement, but also have a much firmer neurobiological basis for processes once considered to be solely the concern of psychology, such as decision-making, memory and learning. As an example, using only flashes of light, it is possible to mimic the sensation of having learnt or seen something new in an animal that has never seen this object before. When the new object is introduced to them in real life, they behave as if they have seen it even though they have not. This technique also has implications for human health and disease, and some of the neurons involved in diseases such as Parkinson’s and Alzheimer’s disease, schizophrenia, depression and addiction have been investigated using optogenetics, helping us on our way to finding effective treatments for these conditions.

The technique is constantly improving, and while there is still much more research to be done before we can say that we understand the brain, it is an exciting development and one with enormous potential. For an excellent longer explanation, take a look at the TED talk by Oxford professor Gero Miesenböck, one of the pioneers of optogenetics: https://www.youtube.com/watch?v=EZ_f3Fc0ZRA. To read some more in depth about the impact optogenetics has had and may have in the future, check out some of the articles from the 2015 Nature edition celebrating 10 years of optogenetic research: https://www.nature.com/collections/tqxhytcpwh/anniversary.