Mar 06 2012

Natural Feeling Neuroprosthetics

Science fiction is full of a future in which we plug our brains into a computer (or a computer into our brains, I guess) and experience a seamless connection to either a virtual world (ala The Matrix) or a robotic machine that we can control as if it were a part of our body. This is called a brain machine interface (BMI), and the applications of this technology would be many and profound.

The question remains, however – will it work? Will the experience be truly seamless? Can our brains adapt to mesh with a virtual reality or control something external? There are two ways you can think about this based upon our current understanding of neuroscience. The first is that BMI will be inherently limited because as the brain develops it adapts to our bodies and the sensory information that it receives. There are also windows of developmental potential, and after our brains develop to a certain point it loses some of its potential to adapt and wire itself to novel input.

We might hypothesize, therefore, that an adult would have a limited capacity to adapt to a BMI. Therefore the experience will seem unnatural and perhaps even unpleasant, and the level of control will be limited and awkward. This is the pessimistic view.

The other factor to consider is brain plasticity – the potential of our brains to make new connections and pathways to rewire itself to new tasks, including recovery from injury or just developing new skills and abilities. This, of course, is the optimistic view. If this view is closer to the truth then there may be no significant limit to the extent that our brains can adapt to neuroprosthetics. That robotic arm may feel just like the arm you were born with – you will feel as if you own it and control it, and that control will be as natural and fine as a biological arm.

I suspect the truth is somewhere between the two extremes of these views, but at present we simply do not know. Existing research has shown that the brain can adapt to and use neuroprosthetics, but it is not clear how complete or natural the control is. One specific issue is whether or not the brain can directly control a neuroprosthetic or whether it requires a proxy movement, such as moving a part of the body, in order to execute a movement of a neuroprosthetic. In other words – do you need to move your arm in order to move a robotic arm, which is then just mimicking the movement of your physical arm?

A new study is the first to show that it may be possible to control a neuroprosthetic without the proxy of physical moving part of the body, adding one bit of information in favor of BMI working seamlessly. From the press release:

To clarify these issues, the scientists set up a clever experiment in which rats could only complete an abstract task if overt physical movement was not involved. The researchers decoupled the role of the targeted motor neurons needed for whisker twitching with the action necessary to get a food reward.

The rats were fitted with a brain-machine interface that converted brain waves into auditory tones. To get the food reward – either sugar-water or pellets – the rats had to modulate their thought patterns within a specific brain circuit in order to raise or lower the pitch of the signal.

They found that the rats were able to modulate their thoughts, without an accompanying physical movement, to either increase or decrease the tone to obtain either food or water as desired. Of course, this is a study in rats, so we can’t ask them how the experience felt. We can also only infer that they were able to choose water vs food, because they balanced both rewards, but perhaps it was mostly random.

This study is interesting but only one tiny baby step in this research. It suggests we can decouple physical movement from neuroprosthetic or BMI control. This is certainly encouraging, specifically for the use of BMI for those who are paralyzed and cannot move.

Where does this leave us? I suspect that control of BMI will be very good, but not quite seamless and not as good as control of our natural bodies. Plasticity is powerful – but it is also not unlimited. For example, studies show that people who learn to play an instrument like the violin change their brain’s wiring through plasticity. For violinists the motor area for their off hand, the one that is fingering the strings, enlarges, giving them more exquisite control. But this is only true for violinists who started playing very young, and kept it up. If you started playing the violin as an adult, your brain will never develop these changes. That suggests a limit to the brain’s plasticity.

This suggests several things to me. First, BMI incorporated as an adult will never be fully seamless or natural. The brain will adapt to the BMI, but that adaptation will be limited. Therefore, BMI will be more effective if incorporated in young children. Perhaps we will see a day when many infants are fitted with a BMI device so that their brain can develop to fully incorporate communication with and control of the BMI. That BMI can then be plugged into a number of external devices or be used for a variety of purposes. It will become an all-purpose extension of the brain – its pathway into the virtual and machine world.

However, the other possibility is that we will develop the technology to allow the adult brain to more fully adapt to a BMI. This may require stem cells or technologies not yet dreamed of. Natural plasticity will likely not be enough, but there may be ways of coaxing the brain into behaving more like an infant brain in this respect.

Extrapolating beyond that puts us back into the world of science fiction. We can speculate about a future in which humans merge fully with our technology. Kurzweil may be correct in that future artificial intelligence will be us. We need not fear future robotic overlords because we will be them. We may plug ourselves (probably wirelessly) into our houses, cars, and spaceships, and control them perfects with thoughts alone. “Telepathic” communication with then be possible, as we could theoretically not just communicate directly from mind to mind, but actually merge our minds with others, or create a network of minds.   Perhaps we will even achieve virtual immortality in this way. Once we achieve seamless BMI a whole new world of possibilities opens up. Imagine having your brain plugged into the cloud in which all human knowledge is accessible at will.  If there is any truth to the notion of the Singularity, in my opinion this is it.

But this is still science fiction. We do not know now long it will take to develop this technology or what unexpected barriers we will encounter along the way. We are also still not sure what the ultimate limits will be. BMI may turn out to be the next flying cars – a vision of the future that is perpetually 20 years away. Or it may be the next iPhone – a technology that will quickly change our lives.

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