Advanced Artificial Limbs Mapped in the Brain
Source: Ecole Polytechnique Federale de Lausanne
Summary: Scientists used a neuroprosthetic approach which reroutes residual limb nerves towards intact muscles and skin regions to control a robotic limb.
Targeted motor and sensory reinnervation (TMSR) neuroprosthetic approach, a surgical procedure on amputees (people who lost all or part of an arm, hand or leg). TMSR can reroute residual limb nerves towards intact muscles and skin regions in order to unprecedentedly control a robotic limb. TMSR has the ability to change the way how the brain processes motor control and somatosensory input. Scientists at EPFL (Ecole Polytechnique Federale de Lausanne) have used an ultra-high field 7 Tesla fMRI (functional magnetic resonance imaging) to show how brain remaps in patients with amputations particularly in the primary motor cortex and somatosensory cortex regions. The findings were published in the journal Brain.
The residual nerves of the amputated limb are transferred for reinnervation and thereby activating muscle targets. In a person fitted with TMSR prosthetic limb sends motor commands to the re-innervated muscles, then his or her movement intentions are decoded and sent back to the prosthetic limb. On the other hand, inducing touch perception on the missing limb is attained by direct stimulation of the skin over the re-innervated muscles is sent back to the brain. Researchers have successfully mapped out all these changes in the cortices of three persons with upper-limb amputations who had undergone TMSR.
Despite the good motor performance, TMSR-enabled artificial limbs still are unable to move and feel like a real limb and are not encoded by the person’s brain as a real limb. These findings have provided the first detailed neuroimaging investigation in people with bionic limbs. The findings also suggested TMSR may counteract poorly adapted plasticity in the cortex in people with lost limbs. Finally, the study indicates that there is a need for further engineering advances which helps in integration of somatosensory feedback into current prosthetics which can enable them to move and feel as real limbs.
More Information: Andrea Serino et al. “Upper limb cortical maps in amputees with targeted muscle and sensory reinnervation”, Brain (2017). DOI: 10.1093/brain/awx242