Repurposing pharmateuticals and developments in prosthetic limbs.

Mar 17, 2016

It is well known that the human brain is a marvelously complex and flexible mechanism, capable of aggregating and processing information from our senses as well as ruminating and calculating based upon the results of other internal processes. It is so complex, in fact, that at this time we can't be sure of what its limits are or what's actually going on in there. People have built entire careers around studying emergent phenomena within the operation of the brain. The day to day operation of the human brain is so complex that it takes very little to tweak its functionality - change the concentration of a hormone one or two points in either direction, and entire modes of thought change. Primates have been eating (or not eating) various things for millennia to change how and what they think. Designer consciousness has long been a dream of transhumanists and psychologists - take a drug here, unlock a dormant function of the brain as long as the organism has a certain concentration of in circulation.

An article published in the journal Frontiers In Systems Neuoscience in December of 2013 described a surprising discovery made by a group of neuroscientists: An anticonvulsant drug used to treat epilepsy called valproate seems to kickstart certain forms of critical period neuroplasticity after they are thought to have ended because the brain has matured. The experiments involved administering valproate to adults without musical training and then trying to teach them how to have perfect pitch. The study chose perfect pitch because there are, so far as is known, no cases of adult humans having successfully gained the ability through study or training. The data gathered by the research group reflects that the group of subjects who were administered valproate scored higher on note and pitch identification tests than the test group that was given a placebo instead, which strongly suggests that they were able to successfully reprogram one of their fundamental perceptual cortices (the auditory cortex), which ordinarily cannot be done after the onset of adulthood.

While this seems kind of pointless the results imply some interesting things. First and foremost, if the auditory cortex can be successfully be reprogrammed then other parts of the brain probably can be as well under the proper conditions. Perhaps visual processing, textual recognition, or memory could be reprogrammed or enhanced; maybe the angular gyrus in the parietal lobe can be reworked to have a greater facility for mathematics. This particular experiment has implications for the acquisition of new spoken languages, in particular tonal languages which are considered by many to be the most difficult to become proficient in.

One of the big drawbacks of prosthetic limbs is that they don't really have a sense of touch. For example, someone using a prosthetic hand cannot tell if they are holding something in the gripper without looking at it. Nor can the wearer determine how strongly the gripper is holding something because the sense of tactile feedback is simply not there. Microcontrollers and clever arrangements of springs and servomotors in the limbs are designed so that enough friction is generated by the gripper to hold most small objects. This is why adding a sense of touch to newer models of prosthetic hands represents a substantial breakthrough. Dennis Sorensen, age 36, lost his left hand in an accident nine years ago. In a surgical procedure carried out in Rome surgeons patched into four sensory nerve trunks in his left arm, and connected them to the electrical actuators in his prosthetic that move the fingers. As the actuators move the fingers of his prosthetic hand they register a certain amount of strain and resistance, and that measurement (probably represented as varying voltage) is transmitted into those sensory nerves. End result: Sorensen was able to feel something in his left hand for the first time in nearly a decade. He was able to recognize the shapes and textures of objects held in his prosthetic hand without looking at them, and characterized the sensations as almost natural.

The electrode implants had to be removed within a month to comply with human testing safety protocols due to the risk inherent in running wires through holes in the skin but the data is both promising and inspiring. Silvestro Micera of the Life Hand 2 Project says that this is the first time in the history of prosthetics that sensory feedback has been used to control a prosthetic limb in realtime. It is hoped that the interface hardware can be miniaturized so that it poses less of a long term risk. Thinking about it a little, a set of short-range wireless transceivers (maybe RF, maybe optical) which can be connected to nerves as well as being fully implanted beneath the skin (reducing the problems posed by transdermal implants) might be usable for both sending commands to prosthetic limbs as well as recieving sensory feedback from them. Perhaps the implanted transceivers could be purely passive, i.e., powered through inductance by circuitry within the replacement limb rather than by implanted power cells (which naturally run down and would require surgery to replace). But that's probably a ways down the line.

In other limb replacement news, a nine year old boy living in Kansas is pleased as punch with his new prosthetic right hand. Matthew (last name not given, probably due to his age) was born with limb difference, which is the name for a family of syndromes that reflect limbs which did not develop identically, and which may not have developed at all. Matthew's right hand has only a thumb and several partial digits. Sixteen year old Mason Wilde, a friend of Matthew's family, fabricated and assembled an open source prosthetic hand on a local library's 3D printer which Matthew wears and uses every day. The hand is dexterous enough to allow the youngster to hold and write with a pencil, an important everyday task for a third grader as well as a testament to the practical usability of the design. The limb cost significantly less to print and build than to purchase (prosthetic hands cost around $18kus a piece, and have to be replaced as the wearer grows), plus it can be repaired much more readily if necessary.

An open message to Matthew and Mason: Find your local hackerspace!