'Virtual touch' tested in monkeys
“Brain implant could help paralysed people regain movement and feeling,” reported The Guardian . The newspaper said that researchers had created a brain implant that allowed monkeys to move a virtual arm and feel objects in a virtual world.
The news story is based on experiments in which researchers inserted electrodes into the brains of two monkeys. The electrodes were placed in the motor cortex, the part of the brain that controls movements, enabling the monkeys to explore virtual objects on a computer screen by moving a virtual arm. Electrical signals sent back from the computer to electrodes in the sensory cortex of the brain enabled the monkeys to distinguish between different objects and also to ‘feel’ the texture of the objects they explored.
This experiment suggests that, with the use of electrical signals to and from the brain, it is possible for primates to control movement and ‘feel’ objects by thought alone, rather than by physical movement and touch.
There is ongoing research into the possibility of using this technique to develop prosthetic limbs or robotic suits for paralysed patients that would not only restore natural movement but also provide tactile feedback.
While this is exciting research, further testing and research is needed before it is known whether similar ‘brain-machine-brain’ techniques could be safely and successfully used in humans.
Where did the story come from?
The study was carried out by researchers from Duke University, US; Ecole Polytechnique Federale de Lausanne, Switzerland, and Edmond and Lily Safra International Institute of Neuroscience, Brazil. It was funded by the National Institutes of Health and DARPA (The Defense Advanced Research Projects Agency) both in the US.
The study was published as a letter in the scientific journal Nature . The study was reported by The Guardian , BBC News and_ The Daily Telegraph._
What kind of research was this?
This was a laboratory experiment in rhesus monkeys. The aim was to explore whether a device could enable the monkeys to exert control over a virtual environment while also feeding back the sensation of touch to their brains; in other words, whether the monkeys could move and ‘feel’ the objects on a screen. The researchers called this device a ‘brain-machine-brain interface’ (BMBI).
The researchers point out that brain-machine interfaces (BMIs) are already involved in the development of robotic arms and muscle stimulators that can perform complex limb movements such as reaching and grasping. They say that while such interfaces could be used to restore motor function in the limbs, so far they have lacked any ability to transmit tactile feedback.
What did the research involve?
The researchers implanted electrodes into the motor cortex and somatosensory cortex of two adult monkeys. The motor cortex is the region of the brain involved in performing voluntary movement and the somatosensory cortex processes input received from sensory cells in the body.
The monkeys were then trained to use a joystick to explore virtual objects on a computer screen. They could manipulate the objects using either a virtual arm or a computer cursor. When the virtual arm interacted with the virtual object, electrical signals were fed back to the somatosensory cortex in the monkeys’ brains creating the sensation of tactile (the feeling of touch) feedback.
In this initial stage of testing, the electrodes that had been implanted in the motor cortex recorded the monkeys’ intentions to move but were not actually moving the virtual arm on the screen – this was being performed by the hand manipulating the joystick. The reason the researchers performed the tests in this way initially was because they weren’t sure whether the electrical signals going to and from the brain would interfere with each other.
In successive stages of the experiment, the joystick was taken away allowing motor signals from the brain to move the virtual hand using the monkey’s intentions only, while electrical signals coming back from the computer to the sensory cortex gave tactile sensations. In this way the researchers had achieved their aim of brain-machine-brain communication.
Once trained, the monkeys had to perform various tasks to test whether they could ‘feel’ objects through the electrical signals in the brain. They had to choose between two visually identical objects onscreen, only one of which was associated with electrical simulation when ‘touched’. They were rewarded with fruit juice for holding the virtual arm over the correct object.
What were the basic results?
The monkeys were able to distinguish between the object that was associated with an electrical stimulation when touched and which produced the reward, and an object that produced neither any stimulation nor a treat.
How did the researchers interpret the results?
The researchers say their BMBI demonstrated ‘bidirectional communication’ between a primate brain and an external actuator (the virtual arm) and such BMBIs can effectively ‘liberate the brain from the physical constraints of the body’. Put simply, they think it possible for the brain to decode information about the sense of touch without direct stimulation of the animal’s skin.
They interpret this to mean that prosthetic limbs for people who are paralysed might benefit from artificial tactile feedback through intracortical microstimulation (ICMS).
Conclusion
This work on non-human primates is part of ongoing research exploring the possibility of developing prosthetic limbs that use brain implants to restore natural movement to paralysed patients. In theory, ‘bidirectional communication’ could lead patients to not only control movement of the prosthetic limb, but also in some way restore the sense of touch. As the researchers say, visual feedback can only go so far in helping you perform normal activities. For example, if you pick up an object, you also need to feel it in your hands to stop you dropping it.
While exciting, this is early research involving implanting electrodes into the brains of rhesus monkeys. It is unknown if a similar technique could be used in humans, or if such a thing would be safe or desirable. There is some way to go and much further research and testing is needed before it is known whether similar brain-machine-brain techniques could result in devices that can restore movement and feeling for paralysed people.
