Under normal circumstances, loss of movement in limbs through accident or illness would leave a person having to lead a life dependent upon others. However, the development of a new generation of brain-directed robotic arms by scientists at America’s Pittsburgh University offers the prospect of far greater independence for those who are paralysed.
Though this is not the first brain-directed robotic arm, the Pittsburgh team’s prosthetic arm offers a far greater level of control and movement than has ever been achieved before.
So when the arm was used by a 52-year-old female tetraplegic, it enabled her to perform a range of tasks including being able to pick up and move several differently shaped objects.
To enable her to do this, two microelectrode arrays were implanted into her brain to create a control pathway between neurones and the wires that lead to the robotic arm itself.
However, it’s the way that the signals from the brain are being interpreted that has allowed the unprecedented extra control and refinement of movement.
For scientists and engineers looking to develop a prosthetic limb that can be controlled by the mind, there is always one major hurdle to overcome. This is to find a way of turning the messages from the brain that express complex limb movement into signals that can be understood by prosthesis and used to create the reliable and accurate movement of it.
To date, this has been done using an algorithm to sift through a library of computer-brain connections to find the one required. However, the Pittsburgh team have approached it from a different angle, employing a model-based algorithm that mimics the way in which an unimpaired brain would normally control limb movement.
It’s this new technique that has created this breakthrough, giving the patient the ability to move the robotic wrist and hand unaided after 14 weeks of training. During this period, her speed of movement also increased significantly as she reduced the time it took to perform tasks by over half a minute.
Action research arm tests (ARATs), more normally used to assess those suffering paralysis through injury or illness, have shown that the patient is able to move the robotic arm with ‘seven degrees of freedom’. This means that she can manoeuvre the limb in three dimensions, orientate it also in three dimensions and grasp in one.
The next stage will be to introduce ‘sensation’ so that the patient is able to discern the difference between smooth and rough surfaces and whether they are hot or cold. The team will also look to develop wireless technology to link the arm and the brain implant.
However, even though the Pittsburgh team have made a significant breakthrough, it will inevitably be some time before brain-directed robotic arms become a practical, everyday solution that can fundamentally transform people’s lives.
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