Increasing mediolateral standing sway is associated with increasing corticospinal excitability, and decreasing M1 inhibition and facilitation

Tulika Nandi, Beth E. Fisher, Tibor Hortobagyi, George J. Salem*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

13 Citations (Scopus)

Abstract

In standing, corticospinal excitability increases and primary motor cortex (M1) inhibition decreases in response to anterior posterior or direction unspecific manipulations that increase task difficulty. However, mediolateral (ML) sway control requires greater active neural involvement. Therefore, the primary purpose of this study was to determine the pattern of change in neural excitability when ML postural task difficulty is manipulated and to test whether the neural excitability is proportional to ML sway magnitude across conditions. Tibialis anterior corticospinal excitability was quantified using motor evoked potential (MEP) and postural sway was indexed using ML center of pressure (COP) velocity. Additionally, we examined inhibition and facilitation processes in the primary motor cortex using the paired pulse short interval intracortical inhibition (SICI) and intracortical facilitation (ICF) techniques respectively. Measurements were repeated in four conditions with quiet stance as a control. Differences between conditions were tested using one-way repeated measures ANOVAs, on log transformed data. Associations were quantified using Spearman's Rank Correlation Coefficient. There was a significant main effect of condition on all the neural excitability measures with MEP (p <0.001) being highest in the most difficult condition, and SICI (p = 0.01), ICF (p <0.001) being lowest in the most difficult condition. Increasing ML COP velocity was significantly associated with increasing MEP amplitude (r = 0.68, p <0.001), but decreasing SICI (r = 0.24, p = 0.03) and ICF (r = -0.54, p <0.001). Our results show that both corticospinal and M1 excitability in standing are scaled in proportion to ML task difficulty.

Original languageEnglish
Pages (from-to)135-140
Number of pages6
JournalGait & Posture
Volume60
DOIs
Publication statusPublished - Feb-2018

Keywords

  • Postural control
  • Mediolateral
  • M1 excitability
  • Center of pressure
  • Transcranial magnetic stimulation
  • TRANSCRANIAL MAGNETIC STIMULATION
  • MOTOR CORTICAL EXCITABILITY
  • TIBIALIS ANTERIOR MUSCLE
  • POSTURAL SWAY
  • SOLEUS MUSCLE
  • INTRACORTICAL INHIBITION
  • UPRIGHT STANCE
  • BALANCE
  • AGE
  • MODULATION

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