September 7, 2012

BCI Controls Robotic Leg Orthosis

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The experimental setup showing the subject suspended in the RoGO, while donning an EEG cap, surface EMG electrodes, and a gyroscope on the left leg. A monitor (not shown), placed in front of the subject at eye-level, presented instructional cues. Photograph courtesy of Po T. Wang, PhD.

A team of researchers from the Long Beach Veterans Affairs Medical Center, California, and the University of California, Irvine, have demonstrated that an able-bodied subject used walking motor imagery to accurately operate a noninvasive brain-computer interface (BCI) controlled robotic gait orthosis (RoGO). This finding represents what they say is the first successful demonstration of a BCI-controlled lower-limb orthosis for independent ambulation. The RoGO has implications for restoring ambulation to individuals with paraplegia due to spinal cord injury (SCI).

Their work is presented in a paper, “Brain-Computer Interface Controlled Robotic Gait Orthosis: A Case Report,” published in the open-access, online archives, It was also presented August 27 at the 34th Annual International Conference of the Institute of Electrical and Electronics Engineers (IEEE) Engineering in Medicine & Biology Society.

The researchers recorded electroencephalogram (EEG) data from an able-bodied subject who alternated periods of walking motor imagery (MI) and standing MI. These data were analyzed to generate an EEG prediction model for online BCI operation. A commercial RoGO system suspended over a treadmill was interfaced with the BCI computer to allow for computerized control. The subject was then asked to imagine standing or walking, in response to computerized cues. Electromyogram (EMG) was measured to rule out BCI control by voluntary leg movement.

According to the study, the subject achieved a high level of control of the BCI-RoGO system after a 20-minute process comprising training data acquisition, calibration, and familiarization. The subject’s online BCI-RoGO operation showed a 100 percent response rate, and by the end of the experiment the subject had no false alarms (movement during “idle” cues).

Although these results provide preliminary evidence that restoring brain-controlled ambulation may be possible, the researchers say that future work is necessary to test this system in individuals with paraplegia due to SCI. Since individuals with SCIs are able to operate the BCI-walking simulator, it is expected that they can readily transfer their skills to the BCI-RoGO system as the able-bodied subject did. If successful, such a system has the potential to be used as a rehabilitation tool for individuals with incomplete motor injuries, or may even justify future development of BCI-controlled lower-limb orthoses for free over-ground walking for individuals with complete paraplegia due to SCI.

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