Long-lasting event-related beta synchronizations of electroencephalographic activity in response to support-surface perturbations during upright stance

Abstract

word count: 299 words Abstract Movement related beta band cortical oscillations, including post-movement beta rebound and desynchronization/synchronization observed during Go/NoGo tasks, have drawn attention in motor control literature, particularly during movements of upper extremities. However, fewer study focused on beta band oscillations during postural control in upright stance. Here, we examined beta rebound and other components of electroencephalogram (EEG) activity during perturbed upright stance to investigate supraspinal contributions to postural stabilization. Particularly, we aimed to clarify the timing and duration of the beta rebound and other components within a non-sustained, but long-lasting, postural recovery process following perturbed stance that occurs much more slowly compared to upper extremities due to a larger time scale of mechanical dynamics. To this end, EEG signals were acquired from nine healthy young adults in response to an impulsive support-surface perturbation, together with the center of pressure (CoP), center of mass (CoM) and electromyogram (EMG) activities of ankle muscles. Event-related potentials (ERPs) and event-related spectral perturbations (ERSPs) were computed using the perturbation onset as a triggering event. Our results indicate that, after shortlatency (<0.3 s) ERPs, powers in high-beta and alpha bands decreased (event-related desynchronizations: ERDs) in the 0.3-0.6 s and 0.3-1.5 s time-intervals after the perturbation onset, respectively. This was followed by long-lasting theta band decrease (ERD) and high-beta increase (event-related synchronization: ERS), implying beta rebound. Specifically, the beta rebound sustained for approximately three seconds from 1.0 to 4.0 s. EMGs of the ankle muscles and joint torques of the ankle and hip were almost completely relaxed in the first half period of the beta rebound. In the remaining period, the CoP and CoM were in their final approach to the equilibrium with amplitudes comparable to those during quiet stance. Possible mechanisms of beta rebound and long-lasting theta-ERD may be related to underlying intermittent control strategy for upright stance.where we assumed that the foot-link is fixed on the moving support surface with no translational and rotational movement (̈F = , ̈F = 0, ̈f = 0). Moreover, we assumed that ( F − ANK ) = 0.02 m,

Cortical Beta Oscillatory Activity Evoked during Reactive Balance Recovery Scales with Perturbation Difficulty and Individual Balance Ability

“…We observed greater modulation of sensorimotor beta oscillations evoked by larger, more challenging balance perturbations, and in individuals with lower balance ability. In contrast to prior studies that have observed beta power modulation beginning prior to the onset of unpredictable balance perturbations [ 35 , 36 , 37 , 38 , 39 , 40 ], we found modulation of beta power occurred ~50 ms after the onset of perturbations. Further, the time course of evoked beta power was similar to that of evoked balance-correcting muscle activity.…”

“…While beta oscillations have been linked to sensorimotor information processing and motor control, beta oscillatory activity in the context of balance-correcting behavior and associations with balance ability are poorly understood. Previous studies have consistently demonstrated that cortical beta activity over central midline scalp regions is modulated during standing balance recovery [ 35 , 36 , 37 , 38 , 39 , 40 ], though there is some discrepancy regarding the directionality of change that may originate from differences in the perturbation and analysis methodologies.…”

Cortical beta oscillatory activity evoked during reactive balance recovery scales with perturbation difficulty and individual balance ability

“…We observed greater modulation of sensorimotor beta oscillations evoked by larger, more challenging balance perturbations, and in individuals with lower balance ability. In contrast to prior studies that have observed beta power modulation beginning prior to the onset of unpredictable balance perturbations (Nakamura et al, 2020;Peterson & Ferris, 2018Solis-Escalante et al, 2019;Varghese et al, 2014Varghese et al, , 2019, we found modulation of beta power occurred ~50 ms after the onset of perturbations. Further the time course of evoked beta power was similar to that of evoked balance-correcting muscle activity.…”

“…In contrast to the transient N1 potential that reflects more general neural features of attention (C. E. Little & Woollacott, 2015;Quant et al, 2004) or threat perception (Adkin et al, 2008;Mochizuki et al, 2010), cortical beta power has greater potential for involvement in balance-correcting behavior because it remains elevated throughout balance recovery with a time course comparable to the balance-correcting motor response. Prior studies have shown beta power modulation beginning prior to the onset of unpredictable balance perturbations (Nakamura et al, 2020;Peterson & Ferris, 2018Solis-Escalante et al, 2019;Varghese et al, 2014Varghese et al, , 2019, making it unclear whether the modulation was occurring in anticipation of, rather than in response to, the balance perturbations. The apparent modulation of beta power prior to perturbation onset in these cases may have resulted from the loss of temporal resolution that occurs with the use of larger sliding time windows that are necessary for the inclusion of lower oscillatory frequencies (e.g.…”

“…While beta oscillations have been linked to sensorimotor information processing and motor control, beta oscillatory activity in the context of balance-correcting behavior and associations with balance ability are poorly understood. Previous studies have consistently demonstrated that cortical beta activity over central midline scalp regions is modulated during standing balance recovery (Nakamura et al, 2020;Peterson & Ferris, 2018Solis-Escalante et al, 2019;Varghese et al, 2014Varghese et al, , 2019, though there is some discrepancy regarding the directionality of change that may originate from differences in the perturbation and analysis methodologies.…”