The day after Tom Holder spoke at the University of Pittsburgh about the importance of animal research, more news is coming from this academic institution.
Every 45 seconds someone in the US gets a stroke, many are left paralyzed, furthermore 14,000 people every year suffer spinal cord injuries which may also result in paralysis. There is therefore huge incentive to learn how to bypass the damaged parts of the brain by a brain-machine interface so that the patients can regain effective movements that would be a huge help in their daily lives. It is not surprising that there has been widespread press coverage of a study published online in Nature yesterday (1) that signalled a major breakthrough in this field.
Using 2 rhesus monkeys Andy Schwartz and his team at the University of Pittsburg have made a huge advance towards that aim. They trained the monkeys to use their own motor cortical activity to control a mechanized arm to feed themselves. The team extracted the control signal from recording from about 50 nerve cells in the animals’ motor cortex. This was far fewer neurons than many researchers thought would be necessary, an important discovery in itself that should make it a little easier to design electrode implants in future. Once the monkeys got used to the system they soon became astonishingly fluid, skilled and expert in moving the robot arm just by altering the firing of their motor cortical neurones. They even learnt to take advantage of the marsh mallows sticking to the robot fingers to speed its delivery to their mouths. Even though clinical use for people with disabilities is still years away because the arm requires large computers, bulky equipment and a full time technician, and the brain-implanted electrodes would not last a lifetime and lack touch feedback from the arm, Schwartz’s achievement is phenomenal and a huge leap towards helping all those people with paralysis.
It is important to emphasise that this work could not have taken place without many years of animal experiments, with monkeys playing a key role (2,3). Andy has been working with monkeys trained to make movements designed to reveal how the motor cortex works for some 20 years. Only monkeys have the kind of control over their hands that we have, so only using monkeys could he work out the kind of control signals that they use to feed themselves. 20 years of monkey experiments (only using 1 or 2 a year) allowed him to ‘take the system to pieces’ and work out how the motor cortical cells control the arm. Obviously these experiments couldn’t be done on humans, they are simply too risky at this early stage in the development of the technology, but now he’s elucidated the control circuitry it will not be long before they’ll be applied to benefiting paralysed humans.
Professor of Physiology, Magdalen College, Oxford University
1) Velliste M. et al. “Cortical control of a prosthetic arm for self-feeding” Nature. 2008 May 28. [Epub ahead of print]
2) Lebedev M.A. and Nicolelis M.A.L. “Brain–machine interfaces: past, present and future” Trends in Neurosciences Volume 29, Issue 9, Pages 536-546 (2006)
3) Schwartz A.B. et al. “Brain-Controlled Interfaces: Movement Restoration with Neural Prosthetics” Neuron Volume 52, Issue 1, Pages 205-220 (2006)