Corticomuscular coherence variation throughout the gait cycle during overground walking and ramp ascent: A preliminary investigation

Abstract

Recent designs of neural-machine interfaces (NMIs) incorporating electroencephalography (EEG) or electromyography (EMG) have been used in lower limb assistive devices. While the results of previous studies have shown promise, a NMI which takes advantage of early movement-related EEG activity preceding movement onset, as well as the improved signal-to-noise ratio of EMG, could prove to be more accurate and responsive than current NMI designs based solely on EEG or EMG. Previous studies have demonstrated that the activity of the sensorimotor cortex is coupled to the firing rate of motor units in lower limb muscles during voluntary contraction. However, the exploration of corticomuscular coherence during locomotive tasks has been limited. In this study, coupling between the motor cortex and right tibialis anterior muscle activity was preliminarily investigated during self-paced over-ground walking and ramp ascent. EEG at the motor cortex and surface EMG from the tibialis anterior were collected from one able-bodied subject. Coherence between the two signals was computed and studied across gait cycles. The EEG activity led the EMG activity in the low gamma band in swing phase of level ground walking and in stance phase of ramp ascent. These results may inform the future design of EEG-EMG multimodal NMIs for lower limb devices that assist locomotion of people with physical disabilities.

Increased central common drive to ankle plantar flexor and dorsiflexor muscles during visually guided gait

“…Coherence increased significantly in the beta and gamma bands in relation to visually guided walking without any changes in the alpha band. Previous findings have suggested that intra-and intermuscular coherence in the beta and gamma bands during walking is related to corticospinal activity, since coherence at similar frequencies are 1) observed for paired EEG and EMG recordings (Petersen et al 2012;Storzer et al 2016;Winslow et al 2016), 2) greatly reduced following lesion of the corticospinal tract (Hansen et al 2005;Nielsen et al 2008;Barthelemy et al 2010;Petersen et al 2013) and 3) increased in relation to maturation of the corticospinal tract (Farmer et al 2007;James et al 2008;Petersen et al 2010). In line with this, corticomuscular coherence in the beta and gamma frequency bands also increased during visually guided walking although it did not reach statistical significance.…”

“…; Winslow et al. ), 2) greatly reduced following lesion of the corticospinal tract (Hansen et al. ; Nielsen et al.…”

Dynamics of corticospinal motor control during overground and treadmill walking in humans

“…A systematic investigation of CMC at different walking speeds may help to resolve the timing of intra-stride modulations of CMC, as the activations patterns of the TA muscle are strongly modulated by walking speed (den Otter et al 2004). The case-reports by Winslow et al (2016) and Brantley et al (2016) investigated CMC during overground walking in a single subject over a single gait cycle: Winslow et al (2016) observed CMC between motor cortex and TA at approximately 18-23 Hz just after heel strike and just after toe-off, whereas Brantley et al (2016) reported CMC between motor cortex and TA at frequencies below 5 Hz throughout the gait cycle. Artoni and colleagues (2017) recently showed a descending connectivity from motor cortical regions to different leg muscles during the swing phase of steady-state treadmill walking.…”

“…High beta CMC was significantly enhanced during overground walking compared to treadmill walking. To our knowledge, no previous study has compared corticospinal dynamics between locomotor tasks, but only investigated it during treadmill walking (Artoni et al 2017; Petersen et al 2012; Winslow et al 2016). However, a number of studies have assessed cortical oscillations during various gait tasks and have found task-dependent differences in cortical beta power (Bruijn et al 2015; Bulea et al 2015; Knaepen et al 2015; Lisi and Morimoto 2015; Oliveira et al 2017b; Sipp et al 2013; Wagner et al 2016; Wagner et al 2012; Wagner et al 2014).…”

“…There are also some initial reports which suggest that these cortical oscillations are transmitted to spinal motoneurons during walking in humans (Artoni et al 2017; Brantley et al 2016; Petersen et al 2012; Winslow et al 2016). In nine participants, Petersen et al (2012) showed corticomuscular coherence (CMC) between electroencephalographic (EEG) and electromyographic (EMG) signals from the tibialis anterior muscle (TA) at 8–12 Hz and 24–40 Hz during walking.…”