Beta activity in the premotor cortex is increased during stabilized as compared to normal walking

Abstract

Walking on two legs is inherently unstable. Still, we humans perform remarkable well at it, mostly without falling. To gain more understanding of the role of the brain in controlling gait stability we measured brain activity using electro-encephalography (EEG) during stabilized and normal walking. Subjects walked on a treadmill in two conditions, each lasting 10 min; normal, and while being laterally stabilized by elastic cords. Kinematics of trunk and feet, electro-myography (EMG) of neck muscles, as well as 64-channel EEG were recorded. To assess gait stability the local divergence exponent, step width, and trunk range of motion were calculated from the kinematic data. We used independent component (IC) analysis to remove movement, EMG, and eyeblink artifacts from the EEG, after which dynamic imaging of coherent sources beamformers were determined to identify cortical sources that showed a significant difference between conditions. Stabilized walking led to a significant increase in gait stability, i.e., lower local divergence exponents. Beamforming analysis of the beta band activity revealed significant sources in bilateral pre-motor cortices. Projection of sensor data on these sources showed a significant difference only in the left premotor area, with higher beta power during stabilized walking, specifically around push-off, although only significant around contralateral push-off. It appears that even during steady gait the cortex is involved in the control of stability.

Corticomuscular control of walking in older people and people with Parkinson’s disease

“…We also pre-processed the EMG recordings by high-pass filtering, rectifying, and demodulating the signals in order to remove low-frequency artefacts and periodic amplitude modulations that could distort the coherence estimates (Boonstra et al 2009, De Marchis et al 2015. Notably, the timefrequency profiles observed in this study are similar to those in multiple previous ambulatory EEG studies (Gwin et al 2011, Cheron et al 2012, Severens et al 2012, Bruijn et al 2015, Bulea et al 2015, Knaepen et al 2015, Bradford et al 2016, Artoni et al 2017, Roeder et al 2018. Importantly, in the current study we found a significant group effect for corticomuscular coherence specifically at lower beta frequencies, but not over a broadband frequency range.…”

“…During walking, beta oscillations have been found to be task-dependent and a number of interpretations have been put forward. For instance, cortical beta oscillations may be related to controlling gait stability (Sipp et al 2013, Bruijn et al 2015, control of step lengthening and shortening adaptations (Cevallos et al 2015, Wagner et al 2016, visuomotor integration (Wagner et al 2014, Oliveira et al 2017, Malcolm et al 2018, speed control (Bulea et al 2015, Lisi & Morimoto 2015, forward propulsion driven by ankle plantar flexors (Jensen et al 2019), erroneous anticipatory postural adjustments during gait initiation (Delval et al 2018), and responding to sensorimotor conflict during perturbations while walking (Peterson & Ferris 2018b). An interesting hypothesis is that activity in the beta band may underpin the temporal coordination of sensorimotor processes (Arnal 2012, Meijer et al 2016, Morillon & Baillet 2017, and hence be involved in the temporal coordination of the heel strike during walking.…”

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

“…Similarly, CMC and ITC of EMG at high beta frequencies (21-30 Hz) was significantly enhanced during overground walking. In line with previous research, this highlights that neural activity is affected by the walking task that is performed (Bradford et al 2016; Bruijn et al 2015; Bulea et al 2015; Kline et al 2016; Knaepen et al 2015; Lisi and Morimoto 2015; Luu et al 2017; Oliveira et al 2017b; Sipp et al 2013; Storzer et al 2016; Wagner et al 2016; Wagner et al 2012; Wagner et al 2014). For instance, theta ERS in motor cortical regions has been found to be increased during more complex walking tasks, such as walking on a balance beam (Sipp et al 2013), on a gradient (Bradford et al 2016), or on an active, user-driven treadmill (Bulea et al 2015).…”

“…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). These studies have suggested that cortical beta oscillations may be related to controlling gait stability (Bruijn et al 2015; Sipp et al 2013), gait adaptations (i.e.…”

“…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). These studies have suggested that cortical beta oscillations may be related to controlling gait stability (Bruijn et al 2015; Sipp et al 2013), gait adaptations (i.e. step lengthening and shortening, Wagner et al 2016), sensory processing of the lower limbs (Wagner et al 2012), visuomotor integration (Oliveira et al 2017b; Wagner et al 2014), and speed control (Bulea et al 2015; Lisi and Morimoto 2015).…”