Chronic paraplegics could partially recover using brain-machine interfaces

Researchers have shown through experiments that it is possible for chronic paraplegics to regain part of their neurological activity thanks to brain-machine interfaces.

Those of you who watched the opening ceremony of the Soccer World Cup in Brazil would remember the young Brazilian man paralyzed from chest down delivering the opening kickoff. This was made possible using a brain-machine interface that not only allows him to control the movements of a lower-limb robotic exoskeleton, but also receives tactile feedback from the exo’s feet.

The work carried out by Walk Again Project (WAP), a non-profit international research consortium, is of immense importance for it gives hopes to millions of chronic paraplegics. WAP has released its first clinical report, describing the findings obtained after the first year of training of the eight paraplegic patients, from January to December 2014. The non-profit research consortium has revealed that the group of patients who have continued to train with the brain-controlled system, including a motorized exoskeleton, have regained the ability to voluntarily move their leg muscles and to feel touch and pain in their paralyzed limbs — despite being originally diagnosed as having a clinically complete spinal cord injury, in some cases more than a decade earlier.

Researchers have also reported in their report that the patients also regained important degrees of bladder and bowel control, and improved their cardiovascular function, which in one case resulted in a significant reduction in hypertension. Scientists involved with the study are of the opinion that the long-term training regimen likely paved way for brain reorganization and activated dormant nerves that may have survived the original spinal injury that occurred 3-14 years earlier.

Until now, no clinical study that employed BMIs in patients suffering from severe spinal cord injuries reported any neurological improvement of their patients. Nicolelis believes that this happened because those studies were very short-termed, and usually involved a single human subject. In addition, in none of these studies did researchers perform any detailed neurological evaluation to search for any clinical improvement.

The brain-machine interface used in this study consisted of multiple EEG recording electrodes embedded in a cap on the patients’ scalp, fitted over the brain areas controlling movement in the frontal lobe. The training protocol was comprised of multiple components. In the virtual reality component, the patients wearing an Oculus Rift head-mounted display were shown a three-dimensional avatar of a person and asked to imagine movements of their own bodies so that they could make the avatar walk. All patients learned to use only their brain activity, recorded through the EEG, to move this avatar body that represented a soccer player walking in a stadium. They also received a continuous stream of tactile feedback, every time the avatar’s feet touched the ground. This feedback was delivered through mechano-vibrating elements attached to the long sleeves of a shirt the patients wore in every session. Tactile feedback was delivered to the skin of the patient’s forearms to ensure full tactile sensitivity. This haptic device was named the “tactile shirt”.

In a second component, the patients used a Lokomat, a robotic gait orthosis, placed on a treadmill, which enables paraplegics to perform walking motions while suspended by a harness. In this component, the patients used the same EEG cap to trigger the Lokomat movements while receiving tactile feedback through the same “tactile shirt”. This “haptic feedback” device received signals from pressure sensors placed on the patients’ legs and feet, which vibrated in a pattern reflecting the patients’ stepping movements.

In a third component, the patients–also wearing the EEG electrodes and the tactile shirt–operated a brain-controlled motorized exoskeleton custom designed for the project by an international team of roboticists. The exoskeleton is the same one the researchers demonstrated at the opening of the 2014 World Cup soccer tournament.

The combination of visual and haptic feedback was critical to the training paradigm as it created a very realistic walking illusion for the patients when they controlled a virtual avatar or the robotic exoskeleton. As an overall result of the 12 months of training, four of the eight patients who were classified as completely paralyzed (ASIA A) were upgraded to incomplete paraplegia (ASIA C) on the ASIA scale. The researchers also found that the patients’ gastrointestinal function improved, with the number of bowel movements directly correlated with the hours of upright walking.

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