First I met a bona fide bionic man in Cambridge – that got me thinking about an essay I wrote whilst in my undergraduate neuroscience days. It explained, in great molecular detail, the obstacles that would have to be overcome for a robotic limb to ever adequately replace the functional repertoire of a severed one. In other words I described what it would take to do a “Luke Skywalker” (for those who actively avoid Star Wars: Luke is the hero who get his arm chopped off in a light sabre battle only to have an operation that replaces the severed limb with a fully-functional robotic one that he controls as effortlessly as the original).
Second I flew to Kyoto – to interview the Godfather of Androids, a man who has created some of the most sophisticated human-like robots in the world. Over ten days of filming I must have come face-to-face with over a dozen robots. Each time I thought back to something that happened, totally spontaneously, during a game of Jenga with Nigel Ackland – my real life Luke Skywalker.
Finally, Nigel performed a manouevre with his robotic arm that no human could with a mortal one. This event brought to mind a classic series of Japanese neurophysiology experiments from the lab of Professor Iriki. These studies expanded our understanding of how brains keep track of the space around us. In particular, how brains distinguish between parts of the environment that can be influenced with a extended arm (plus any tool that provides an extension), and parts that cannot (NB see in particular the original observations from 1996).
Consequently, this month’s brain blog is dedicated to a combination of…
Robotic Technology, Human Determination & Neuroplasticity
The parietal cortex of the primate brain (including the human primate) is responsible for, among several other important functions, our awareness of space. For example, damage to the patch of brain tissue that resides where the parietal lobe borders its temporal and occipital lobe neighbours can lead to neglect if it occurs on the right side of the head (See the images in this free classic paper on neglect if you want to see exactly where in the brain this is) – resulting in the person’s awareness of the left side of everything being highly compromised. Give someone with neglect a piece of paper with circles drawn all over it, asking them to place a mark at the centre of each, they only mark circles on the right side of the page. Ask them to draw a clock face and they will not draw the numbers on the left side (i.e. having successfully drawn a circle and the hours from 12 to 6 on the right hand side, they’ll typically omit the hours of 7 – 8 – 9 – 10 and 11 because they lack awareness of what should be on the left side of a clock face). They will only eat food from the right side of their plate. They will often even only shave the right side of their face, dress the right side of their body. Their awareness of “leftness” has been fundamentally compromised. Such is the importance of the parietal cortex to our awareness of space.
Towards the end of the 90’s and early 00’s researchers working with Japanese macaques trained to reach for food rewards observed that certain neurons would become activated if the treat was placed within arm’s reach. If the primates were provided with a croupier’s rake (usually used in casinos to collect up chips on gambling tables) then neurons representing nearby space that was previously out of reach would become activated once they gained experience using this simple tool to drag the food rewards towards them. The researchers even took it a step further by providing two rakes, one with a short handle and one with a long handle. Neurons representing space out of reach with the short handled rake became recruited into the “network of reachable space” when the macaques figured out they could use the short rake to pull the long rake closer and then use this to drag the treat from the opposite side of the table. Keep this in mind as you read the following account of bionic brain adaptation.
Bionic Brain Adaptation?
Nigel Ackland is a real life bionic man since a nasty industrial accident left his arm mangled and several subsequent botched surgeries led to his decision to have his right arm amputated from the elbow down. Shortly after this operation, he started to develop pain in his phantom limb. His NHS-issued “pincer” enabled him to gain some additional dexterity, but it did little to diminish the phantom sensation of his fingers and wrist locked into an extremely uncomfortable position. However once he started using a cutting-edge bionic arm, equipped with various pre-programmed five fingered hand movements operated via neuronal signals passing from his brain to the muscles at the end of his arm stump, not only did the phantom limb pain start getting better, but the phantom limb started extending gradually from his stump into the hand and fingers of his bionic arm.
Whilst playing Jenga with him for my new series Nigel did something quite remarkable, triggering the memory of those Japanese macaques. Reaching with his bionic arm to grab an awkwardly positioned brick, from his side of the table he could only present the back of his hand to the block he was after. Unlike the rest of us mere mortals Nigel can rotate the hand of his bionic arm at the wrist by 360 degrees. To reach the brick in question he simply rotated his hand 180 degrees to face the other way, and then grabbed the block he was after with his bionic thumb, fore- and middle fingers in the usual way. It immediately occurred to me that people with bionic limbs – who can do things a normal human limb can not – may be awakening neurons in their parietal cortex that represent areas of space that have never before been recruited into the “network of reachable space” in the history of our species. Now that is very cool.
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