Neuroscientist; Director, Social Brain Lab, Netherlands Institute for Neuroscience; Author, The Empathic Brain

Over the past decade, with the discovery of optogenetics, neuroscience has thrown open a door that seemed closed forever. Before optogenetics, our ability to record the activity of cells in the brain was sophisticated, and we understood that mental states are represented in the distributed pattern of many cells. Our emotions, our thoughts, and what we perceive is the activity of millions of cells. What we lacked was the ability to trigger a similar state in the brain on command. Neuroscience was a spectator of the mind—not an actor. With the advent of optogenetics this is currently changing.

Optogenetics is a surprising new field of biotechnology that gives us the means to transform brain activity into light and light into brain activity. It allows us to introduce fluorescent proteins into brain cells to make cells glow when they are active—thereby transforming neural activity into light. It also allows us to introduce photosensitive ion channels into neurons, so that shining light on the cells triggers activity or silences neurons at will—thereby transforming light into neural activity. Combined with modern technologies to record light from neurons deeper and deeper in the brain, and to guide light onto individual neurons, we have crossed a frontier that only a decade ago seemed far far away: the ability not only to record the distributed patterns of brain activity that make up our percepts, thoughts, and emotions but, for the first time, to selectively recreate arbitrary states in the brain—and hence, the mind.

A small number of experiments have demonstrated the potential of this technique. For instance, mice were made to experience fear. Using optogenetics, the pattern of neural activity that was triggered during the original experience was later reactivated, and the mice froze in fear once again. Neuroscience has become a protagonist. The science fiction scenario of "total recall," in which Arnold Schwarzenegger was implanted with memories he never had, now becomes tangible. In another set of experiments, the activity of cells in one animal's brain was recorded and imposed on corresponding cells in the brain of another animal's that was then able to take decisions based on what the other animal was feeling.

I foresee that the ability to measure and recreate brain activity at the level of specific neurons at will is about to transform us in ways that no other invention ever has. The invention of fire, of the wheel, of antibiotics or the Internet changed how we live our lives in profound ways. It made our lives safer, more comfortable, and more exciting. But they have not changed who we are. Being able to record and manipulate brain activity will change who we are. It will serve as an interface through which computers can become part of our brain, and through which our brains could directly interface with each other.

When we observe a baby grow into a child, we witness how profoundly a person changes while connections in her brain allow her to tap into the resources of new brain regions. Soon, for some of us, this process will continue beyond the confined space of our body while optogenetic-like technologies will allow our minds to encompass the world of computers. Who will we become? What will the world look or feel like sensed directly not only with our six senses, but with all the sensors of the Internet of things? What would negotiations for the world climate feel like if we could directly connect with the brains of the people around us and experience the ultimate form of empathy? How will our societies deal with a transition phase in which neuro-enhancement will be affordable to some of us and not to others? In which some will have amazing powers of thought while others will remain confined to their own brain?