How do different movement references influence ERP related to gait initiation? A comparative methods' assessment

Background: Movement-Related Cortical Potentials (MRCPs) are widely used in studying brain dynamics of motor control. However, limited information is available on complex tasks such as locomotion for which the appropriate identification of gait initiation trigger is still a technical challenge. Thus, it is conceivable that recorded brain activity may vary due to the instrument used to provide the temporal trigger. Therefore, a comparative assessment was performed to determine whether and how trigger identification techniques affect the MRCP in gait initiation. New Method: Eleven able-bodied young participants performed 200 forward- and 200 backward-oriented self-initiated steps. Brain activity was recorded through 64-channel electroencephalography. Four different triggering techniques were tested based on measurements of surface electromyography, stereophotogrammetry and forceplates. Results: Repeated-Measures ANOVAs on the mean amplitude of the Bereitschaftspotential and on both peak amplitude and latency of the motor potential showed a main effect of the triggering technique (p < 0.003). Specifically, force plates signal amplitude (−11.56 ± 1.4 μV) was larger than stereophotogrammetry (−5.0±0.5 μV and −6.5 ± 1 μV) and electromyography (−7.2 ± 0.9 μV). Comparison with Existing Method(s): Considering the gait initiation task, no previous study has performed a comparison between the MRCPs observed by triggering the same signal with different approaches. Conclusion: Different instruments identify triggers that vary in terms of time delay, resulting in different amplitudes and timing of the MRCPs. The comparative analysis indicates that forceplate allows to obtain the best MRCP trigger to study gait initiation, in terms of signal strength, cost and set up time.