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Global Translational Medicine BCI-FES with static magnetic field in SCI

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Board hardware. The OpenVibe software platform is used skin impedance. The frequency parameters of the electrical
for the acquisition of signals and consists of an open-source stimulation were: 1 kHz carrier frequency (positive: 200 μs +
tool in C++ that can be customized for different purposes. negative: 200 μs + off: 800 μs); 20 – 40 Hz modulated frequency
The EEG acquisition, pre-, and processing methods were (24 ms active period) to rise and decay pulse trains. The
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based on those described by Broniera Junior et al. After amplitude was modulated based on the instant of maximum
the EEG electrodes are properly positioned, the training electrically stimulated extension. During the feedback
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of the sNES begins, which is divided into two phases: the phase, communication took place through Bluetooth with an
calibration phase, in which the acquisition of the sNES and electrical stimulator, which initiated activation. The activation
adjustment of the classifier (common spatial pattern [CSP] condition of sFES occurs when the probability of similarity of
filter and linear discriminant analysis [LDA]) are carried the classifier output signal is ≥72%. The equipment assembly
out, and the feedback phase. In the calibration phase, the for the participant is illustrated in Figure 2.
participant was instructed to perform knee extension motor
imagery or remain inactive. The testing procedure was 2.5. Data analysis
adapted from Abdalsalam et al., where participants looked The analyses conducted in this pilot study were inherently
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at a reference while simultaneously receiving instructions descriptive and did not involve the application of statistical
to perform motor imagery. In this study, an instructor was tests.
introduced to observe the movement guidelines provided by
the software and reproduce them physically. The instructor 3. Results
was seated in front of the participant, giving the voice The present study analyzed the feasibility of applying
command to imagine the extension movement and perform the sNES-sFES interface with a static magnetic field to a
the movement simultaneously, or the instructor could person with a complete SCI.
provide both voice and motor commands for the participant
to remain inactive. Five to ten repetitions were performed 3.1. Neuromuscular assessment
with an average duration of 8s for two different classes: (i) During the neuromuscular evaluation, the participants
Motor imagery and (ii) rest. The sequence of motor imagery did not experience simultaneous muscle spasms. In both
classes presented to the individual was random to avoid the pre- and post-evaluations, the sEMG-RMS values were
bias. In the feedback phase of the sNES, participants were 0% (about the biceps brachii muscle in the pre-evaluation
again instructed to imagine the movement indicated by the [Section 2.2.3]) for the evaluated muscles, rectus femoris,
instructor. At each motor imagery test, new data acquisition and vastus lateralis, bilaterally. Owing to the low value
from the sNES channels was performed, and simultaneously, (indicating only electrical noise), sEMG-MDF analysis was
the classifier produced a real value, quantifying the class unfeasible.
probability associated with the participant brainwave
response. Once calculated, the probability of class 3.2. Spasticity
association (actual value from 0 to 100 %) was transferred The results of assessing the muscle tone of the knee extensors
from the OpenVibe software to a network-based interface and plantiflexors ranged from 1 (increased tone at the
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(VRPN: Virtual-Reality Peripheral Network) developed in
C++ in the Microsoft Visual Studio environment. The beginning or end of the range of motion) to 1+ (increased
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sNES received by the VRPN were processed and sent in tone in less than half of the range of motion, manifested
binary form through Bluetooth to the electrical stimulator. by abrupt tension followed by minimum resistance). In
most sessions, the pre-intervention (intraday) muscle tone
2.4.3. Surface functional electrical stimulation assessment was 1+. The exceptions were the third from
the last and last sessions, with the pre-outcome being 1.
For artificial muscle activation, an electrical stimulator was In the post-intervention (intraday) assessment, there was a
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customized exclusively for this work, following the criteria reduction in muscle tone in most sessions.
outlined in the IEC 60601-2-10 standard. Two self-adhesive
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electrodes, sized 5 × 9 cm, were placed in the anterior region 3.3. Interventions
of the volunteer’s right thigh according to the methodology
described by Krueger et al. One of the electrodes was 3.3.1. Static magnetic field
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positioned at the lower edge, 3 cm from the base of the In the present study, the SMF was used in association with
patella, and the other over the femoral triangle to stimulate NES-FES, with a total duration of approximately 1 h. We
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the quadriceps muscle group through the femoral nerve. did not identify an improvement in the neuromuscular
According to Krueger et al., after fixing the electrodes, condition, possibly due to factors related to the severity of a
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an interval of 10 min was used to stabilize the electrode- complete and chronic SCI in returning muscle contractions.
Volume 3 Issue 1 (2024) 5 https://doi.org/10.36922/gtm.2285