title: Importance of optic flow for postural stability of male and female young adults.
abstract: OBJECTIVE
  A feedback control process based on self-motion perception contributes to postural stability; however, little is known about the visual modulation of postural muscles. The aim of this study was to investigate the effect of optic flow stimuli, presented full field, in the peripheral and foveal visual field, on muscular activation. Then, we assessed the correlation between optic flow, muscle activity and body sway in male and female subjects.
  
  
  METHODS
  We used surface electromyography (EMG) and stabilometry on 24 right-handed young adults. We recorded the bilateral activation of tibialis anterior, gastrocnemius medialis, biceps femoris and vastus medialis. EMG and center of pressure (COP) signals were acquired simultaneously. EMG signal amplitude was computed as root mean square normalized by baseline.
  
  
  RESULTS
  We found a significant effect for muscles, gender and an interaction effect of muscle by gender (ANOVA, p < 0.001). Results showed different postural alignments in males and females. The COP spatial variability during peripheral stimuli was generally reduced. The prevalent direction of oscillation evoked by peripheral stimuli was clustered, while foveal and random stimuli induced distributed and randomized directions. Also for muscle activity, we found gender differences in the prevalent oscillation distributions evoked by optic flow.
  
  
  CONCLUSIONS
  Visual stimuli always evoke an excitatory input on postural muscles, but the stimulus structure produces different postural effects. Peripheral optic flow stimuli stabilize postural sway, while random and foveal optic flow provoke larger sway variability similar to those evoked in the absence of visual stimulation.
authors.affiliation: Department of Biomedical and Neuromotor Sciences, University of Bologna, Piazza di Porta S. Donato, 2, 40126, Bologna, Italy, milena.raffi@unibo.it.
authors.forename: Milena
authors.initials: M
authors.lastname: Raffi
authors.forename: Alessandro
authors.initials: A
authors.lastname: Piras
authors.forename: Michela
authors.initials: M
authors.lastname: Persiani
authors.forename: Salvatore
authors.initials: S
authors.lastname: Squatrito
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology; D057849:Optic Flow; D004856:Postural Balance; D012737:Sex Factors