title: Cortical contributions to control of posture during unrestricted and restricted stance.
abstract: There is very little consensus regarding the mechanisms underlying postural control. Whereas some theories suggest that posture is controlled at lower levels (i.e., brain stem and spinal cord), other theories have proposed that upright stance is controlled using higher centers, including the motor cortex. In the current investigation, we used corticomuscular coherence (CMC) to investigate the relationship between cortical and shank muscle activity during conditions of unrestricted and restricted postural sway. Participants were instructed to stand as still as possible in an apparatus that allowed the center of mass to move freely ("Unlocked") or to be stabilized ("Locked") without subject awareness. EEG (Cz) and electromyography (soleus and lateral/medial gastrocnemii) were collected and used to estimate CMC over the Unlocked and Locked periods. Confirming our previous results, increases in center of pressure (COP) displacements were observed in 9 of 12 participants in the Locked compared with Unlocked condition. Across these 9 participants, CMC was low or absent in both the Unlocked and Locked conditions. The results from the current study suggest that this increase is not associated with an increase in the relationship between cortical and shank muscle activities. Rather, it may be that increases in COP displacement with locking are mediated by subcortical structures as a means of increasing sway to provide the central nervous system with a critical level of sensory information.
authors: School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada.
authors: Chantelle D
authors: CD
authors: Murnaghan
authors: Jordan W
authors: JW
authors: Squair
authors: Romeo
authors: R
authors: Chua
authors: J Timothy
authors: JT
authors: Inglis
authors: Mark G
authors: MG
authors: Carpenter
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009068:Movement; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology; D004856:Postural Balance; D012149:Restraint, Physical
keywords: balance; coherence; exploratory behavior; postural sway; sensory