title: Age-related decrease in motor cortical inhibition during standing under different sensory conditions.
abstract: BACKGROUND
  Although recent studies point to the involvement of the primary motor cortex in postural control, it is unknown if age-related deterioration of postural control is associated with changes in motor cortical circuits. We examined the interaction between age and sensory condition in the excitability of intracortical motor pathways as indexed by short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) during standing.
  
  
  METHODS
  We used magnetic brain stimulation to evoke SICI and ICF in 11 young (range 21-25 years) and 12 healthy old adults (range 60-74 years) while they stood on a rigid platform or foam, with the eyes open or closed.
  
  
  RESULTS
  There was an overall age-related 43% reduction in SICI (p = 0.001). SICI lessened when standing on foam in old (31%) but not in young (1%) adults (condition × group interaction, p = 0.049). This reduction was associated with increases in center of pressure velocity (r = -0.648, p = 0.043). Age (p = 0.527) and sensory conditions (p = 0.325) did not affect ICF.
  
  
  CONCLUSIONS
  Motor cortical circuits controlling leg muscles are modulated differently in healthy old vs. young adults during upright posture. Future experiments will clarify whether this difference mediates impaired postural control or serves as a compensatory mechanism to counteract postural instability.
authors: Center for Human Movement Sciences, University of Groningen, University Medical Center Groningen Groningen, Netherlands.
authors: Selma
authors: S
authors: Papegaaij
authors: Movement and Sports Science, Department of Medicine, University of Fribourg Fribourg, Switzerland.
authors: Wolfgang
authors: W
authors: Taube
authors: Center for Human Movement Sciences, University of Groningen, University Medical Center Groningen Groningen, Netherlands.
authors: Margot
authors: M
authors: Hogenhout
authors: Laboratory of Applied Biology, Faculty for Motor Sciences, Université Libre de Bruxelles Brussels, Belgium.
authors: Stéphane
authors: S
authors: Baudry
authors: Center for Human Movement Sciences, University of Groningen, University Medical Center Groningen Groningen, Netherlands ; Faculty of Health and Life Sciences, Northumbria University Newcastle Upon Tyne, UK.
authors: Tibor
authors: T
authors: Hortobágyi
keywords: aging; balance; brain aging; short-interval intracortical inhibition; transcranial magnetic stimulation