Something as simple as picking up a cup of tea requires an awful lot of action from your body. Your arm muscles fire to move your arm towards the cup. Your finger muscles fire to open your hand then bend your fingers around the handle. Your shoulder muscles keep your arm from popping out of your shoulder and your core muscles make sure you don’t tip over because of the extra weight of the cup. All these muscles have to fire in a precise and coordinated manner, and yet your only conscious effort is the thought: “I know: tea!”
This is why enabling a paralysed limb to move again is so difficult. Most paralysed muscles can still work, but their communication with the brain has been lost, so they are not receiving instructions to fire. We can’t yet repair damage to the spinal cord so one solution is to bypass it and provide the instructions to the muscles artificially. And thanks to the development of technology for reading and interpreting brain activity, these instructions could one day come direct from a patient’s mind.
Could this technology allow people to work again? Zaikina/Shutterstock
We can make paralysed muscles fire by stimulating them with electrodes placed inside the muscles or around the nerves that supply them, a technique known as functional electrical stimulation (FES). As well as helping paralysed people move, it is also used to restore bladder function, produce effective coughing and provide pain relief. It is a fascinating technology that can make a big difference to the lives of people with spinal cord injury.
Dimitra Blana and her colleagues at Keele are working on how to match this technology with the complex set of instructions needed to operate an arm. If you want to pick up that cup of tea, which muscles need to fire, when and by how much? The firing instructions are complicated, and not just because of the large number of core, shoulder, arm and finger muscles involved. As you slowly drink your tea, those instructions change, because the weight of the cup changes. To do something different, like scratch your nose, the instructions are completely different.