In a first-ever demonstration of a two-way interaction between a primate brain and a virtual body, two monkeys trained at the Duke University, Durham, North Carolina, Center for Neuroengineering learned to use electrical brain activity alone to move an avatar hand and identify the texture of virtual objects. This method of feeling without touching may allow people with paraplegia or limb loss to interact with the world using neural-prosthetic devices that send sensations directly to the brain. The work was funded by the U.S. National Institutes of Health.
Researchers describe the demonstration as “liberating the brain from the physical limits of the monkey’s body.” Photograph courtesy of Katie Z. Zhuang, Nicolelis Lab, Duke University.
“Someday in the near future, quadriplegic patients will take advantage of this technology not only to move their arms and hands and to walk again, but also to sense the texture of objects placed in their hands, or experience the nuances of the terrain on which they stroll with the help of a wearable robotic exoskeleton,” said study leader Miguel Nicolelis, MD, PhD, professor of neurobiology at Duke University Medical Center and co-director of the Duke Center for Neuroengineering.
Although the virtual objects employed in this study were visually identical, they were designed to have different artificial textures-expressed as a pattern of minute electrical signals transmitted to the monkeys’ brains-that could only be detected if the animals explored them with virtual hands controlled directly by their brains’ electrical activity. Three different electrical patterns corresponded to each of three different object textures.
Because no part of the animals’ real body was involved in the operation of this brain-machine-brain interface (BMBI), these experiments suggest that in the future patients with paraplegia due to a spinal cord lesion may take advantage of this technology, not only to regain mobility, but also to have their sense of touch restored, said Nicolelis, who was the senior author of the study published in the journal Nature on October 5.
“Such an interaction between the brain and a virtual avatar was totally independent of the animal’s real body, because the animals did not move their real arms and hands, nor did they use their real skin to touch the objects and identify their texture,” Nicolelis said. “It’s almost like creating a new sensory channel through which the brain can resume processing information that cannot reach it anymore through the real body and peripheral nerves.”
The combined electrical activity of populations of 50 to 200 neurons in the monkeys’ motor cortex controlled the steering of the avatar arms, while thousands of neurons in the primary tactile cortex were simultaneously receiving continuous electrical feedback from their virtual hands’ palms that let the monkeys discriminate between objects, based on their texture alone. It took one monkey four attempts and another nine attempts before they learned how to select the correct object during each trial. Several tests demonstrated that the monkeys were actually sensing the object and not selecting them randomly.
“The remarkable success with non-human primates is what makes us believe that humans could accomplish the same task much more easily in the near future,” Nicolelis said, adding that the findings provide further evidence that it may be possible to create a robotic exoskeleton that patients with paraplegia could wear in order to explore and receive feedback from the outside world.
Such an exoskeleton would be directly controlled by the patient’s voluntary brain activity in order to allow the patient to move autonomously. Simultaneously, sensors distributed across the exoskeleton would generate the type of tactile feedback needed for the patient’s brain to identify the texture, shape, and temperature of objects, as well as many features of the surface upon which they walk.
Other study authors include Joseph E. O’Doherty, PhD, Mikhail A. Lebedev, PhD, and graduate research assistants Peter J. Ifft, and Katie Z. Zhuang, all from the Duke University Center for Neuroengineering, and doctoral assistant Solaiman Shokur, and Hannes Bleuler, PhD, from the École Polytechnique Fédérale de Lausanne (EPFL), Switzerland.
This story has been adapted from materials provided by Duke University.
