It is somewhat Ironic, that as I write this month's blog, I am in the middle of one of two conferences on the brain and neural engineering. Each year the Society for Neuroscience holds their annual meeting in late October-early November. The Engineering in Medicine and Biology Society of the IEEE holds their Neural Engineering meeting every two years. This year sees the confluence of both meetings back-to-back in San Diego, resulting in 8 days of immersion in in brain science and engineering.
So, here I sit, after a couple of days of hearing and reading about prosthetics and brain-computer interfaces - trying to condense some very important new findings for our readers. It's not a bad place to be - I am high in a hotel tower overlooking the San Diego Bay, with the night-time lights twinkling on the ships and aircraft. Perhaps the two most heartening developments reported in this and a couple of other conferences I have attended this fall are in the fields of neural -robotics (robotic limbs controlled by signals from the brain) and repair of damaged spinal cords.
Here is a segment of last Spring's 60 Minutes episode detailing the prosthetic arm developed by a DARPA-funded program called "Revolutionizing Prosthetics":http://www.cbsnews.com/video/watch/?id=50137987n
I highly encourage readers to check out this and the related videos to set the stage for our current discussion. So, what is new? Well, the robotic arm shown in the video is strictly one-way control - it can be moved by the brain, but there is no sense of position, touch or movement feeding back into the brain. But the good news is that sometime in the next year, one or more patients will be testing a version of this arm with sensory feedback, and it turns out that we may not have to fully duplicate the complete sensory input signals to make the prosthetic effective. The brain is incredibly flexible, and can learn to use whatever signals are present to at least encode position and movement information. In fact, one of the most important training steps in allowing a patient to learn how to move a prosthetic is the ability to see where the prosthetic is going: a blindfolded patient has much worse control than one actively looking at the hands and fingers of the prosthetic.
The second incredible development comes from restoring the ability to walk in patients with spinal cord damage. It's still just in rats and mice, but Dr. Gregoire Cortine of Ecole Polytechique Federale de Lausanne (Switzerland) has demonstrated the ability to restore normal walking movements in animals with spinal damage that leaves the animals unable to move their lower limbs. (See the video here: http://www/project-rewalk.com
) Incredibly, this technique does not require signals directly from the motor cortex of the brain, but relies on the fact that the spinal cord exerts a lot of control on walking via two systems of neurotransmitter chemicals that help to produce the bend-flex motions required to keep the legs and body in balance. Dr. Cortine's lab uses electrical and chemical stimulation directly in the spinal cord to restore "normal" steps and walking movements, and can even change step speed, strength and height by changing the frequency of the electrical stimulation! This isn't completely
voluntary muscle movement, but again, it taps into the incredible flexibility of the brain (and make no mistake, the spinal cord is
part of the brain) to work around damage.
So, what does this have to do with the stated
topic for this month - the Atom Control SSI? Everything!
A very important feature of the SSI that I neglected to emphasize last month is that direct control via the pre-central gyrus absolutely requires feedback from the manipulated system to provide precision and control of manipulated atoms. Like the motor system in pre-central gyrus, the sensory system in post-central gyrus is mapped to a nearly symmetric set of limbs, body regions and muscle groups:[Image is public domain, adapter from Wilder and Penfield]
This means that almost directly opposite the hand control area of the motor cortex is the hand sensory (tactile) area providing feedback about what the hands touch
during that movement. In addition, we will need some feedback in the vision control system - since a key element of the research mentioned earlier is that the actual sight
of the prosthetic limb is less important to the feedback as the movement
of the eyes and field of view to track and sweep across the visual environment which includes the moving limb. Thus the Atom Control SSI will need to be connect with pre and post-central gyrus at the point marked "hands" and will also need some connection with the "eyes" region to fool the brain into thinking the player is "seeing" and "feeling" the atoms being manipulated![Image adapted from public domain by R. Hampson]
And of course, practice makes perfect. The nervous system is highly flexible and adaptive; learning to be effective with any implant as proposed by the Escaping Titan SSIs will require use, practice and letting the brain figure out how to incorporate these new tools. This will probably occur as the brain begins to treat the SSI just like a pair of hands, albeit with very tiny, precise motions!
Next week marks a year since this forum was formed, and we have nearly come to the end of a year of Neuroscience and Escaping Titan. Next month we'll take a look back at our year, and discuss some more of the ways that current day science is rapidly trying to outpace science fiction! Take care of your brain, and I'll be taking notes at the conferences about new ways to help you do exactly that...