Spinal cord injury (SCI) can be a permanent and often devastating life event for some patients, causing loss of movement in limbs or, in some cases, complete paralysis of the body. Injury to the spinal column can be divided into two different types, namely, a complete spinal cord injury involving permanent damage to the spinal cord resulting in paraplegia or tetraplegia, or an incomplete spinal cord injury referring to partial damage to the spinal cord where the person retains the limited ability to move and feel or touch.

Treatment of SCI currently involves surgery or physiotherapy, with much work concentrated in Brain-Computer Interfaces (BCIs) whose main premise is melding the brain with synthetic prosthesis or implants to restore movement or functionality in SCI.

For researchers developing BCIs the restoration of limb functionality not only involves the reanimation of movement in SCI patients but it is also essential to reinstate the sense of touch as part of this process. However, the restoration of both these functionalities simultaneously in severe SCI is yet to be accomplished.

Restoring touch in spinal injury

Now, a study from researchers led by the Battelle Memorial Institute manufactures a BCI with the ability to simultaneously restore both motor function and the sense of touch in a person with a clinically complete spinal cord injury. The team states technologies with the ability to return both movement and sensation back to their users have the potential to greatly improve independence and the quality of life. The opensource study is published in the journal Cell.

Recent studies from the group involved a 28-year-old man who suffered a complete spinal cord injury during a diving accident in 2010. Since 2014 the patient has been working with engineers on the NeuroLife project to restore function to his right arm. The participant had a microelectrode implanted into his left primary motor cortex linked to a system of electrodes on his skin via artificial intelligence.

This BCI uses wires to route movement signals from the brain to the muscles, bypassing the patient’s SCI, providing enough control over his arm and hand to lift a coffee mug, swipe a credit card, or play Guitar Hero, however, the original system gave no sensory feedback. The current study engineers a BCI with the ability to detect learned memories of touch in the brain of a patient with SCI to enable the participant to move their paralyzed arm whilst simultaneously allowing them to feel objects.

Harnessing the ‘memory’ of touch

The current study identifies the phenomenon of residual touch, where the brain remembers the sense of touch without being able to feel objects or sensation in the real sense. This residual touch was identified by the novel BCI in the patient’s motor cortex even though their arms have lost their nerve-based connection to the brain due to an SCI. Results show this signal, which exists below the threshold of perception, was successfully detected in the brain, rerouted via the BCI, and sent back to a haptic system to restore the sense of touch.

Haptic technology is where forces, vibrations, or motions are applied to the user to create the experience of touch. Data findings show the novel BCI allows the sense of residual touch coming from the participant’s skin to travel back to his brain enabling him to feel and pick up objects through a haptic feedback loop.

Movement & touch in tetraplegia

Results show their novel BCI enabled the patient to reliably detect large objects by touch alone, with the system reanimating movement and touch simultaneously. The lab states this ability to experience enhanced touch during movement gave the patient a greater sense of control, allowing him to do things more quickly. They go on to add their BCI system also gauges how much pressure is needed when handling a soft or hard object or when picking up objects of varying weight and fragility.

The team surmises they have successfully used a BCI to restore movement and the sense of touch in the paralyzed arm of a patient who suffered a complete SCI in 2010. For the future, the researchers state they are working on a portable BCI system for tetraplegic individuals to use in the home to improve their daily lives.

Source: Battelle Memorial Institute

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