Paralysis or amputation of an arm results in the loss of the ability to orient the
hand and grasp, manipulate, and carry objects, functions that are essential for activities
of daily living. Brain-machine interfaces could provide a solution to restoring many
of these lost functions. We therefore tested whether an individual with tetraplegia
could rapidly achieve neurological control of a high-performance prosthetic limb using
this type of an interface.
We implanted two 96-channel intracortical microelectrodes in the motor cortex of a
52-year-old individual with tetraplegia. Brain-machine-interface training was done
for 13 weeks with the goal of controlling an anthropomorphic prosthetic limb with
seven degrees of freedom (three-dimensional translation, three-dimensional orientation,
one-dimensional grasping). The participant's ability to control the prosthetic limb
was assessed with clinical measures of upper limb function. This study is registered
with ClinicalTrials.gov, NCT01364480.
The participant was able to move the prosthetic limb freely in the three-dimensional
workspace on the second day of training. After 13 weeks, robust seven-dimensional
movements were performed routinely. Mean success rate on target-based reaching tasks
was 91·6% (SD 4·4) versus median chance level 6·2% (95% CI 2·0-15·3). Improvements
were seen in completion time (decreased from a mean of 148 s [SD 60] to 112 s )
and path efficiency (increased from 0·30 [0·04] to 0·38 [0·02]). The participant was
also able to use the prosthetic limb to do skilful and coordinated reach and grasp
movements that resulted in clinically significant gains in tests of upper limb function.
No adverse events were reported.
With continued development of neuroprosthetic limbs, individuals with long-term paralysis
could recover the natural and intuitive command signals for hand placement, orientation,
and reaching, allowing them to perform activities of daily living.
Defense Advanced Research Projects Agency, National Institutes of Health, Department
of Veterans Affairs, and UPMC Rehabilitation Institute.
Copyright © 2013 Elsevier Ltd. All rights reserved.