Right hemisphere in visual regulation of complex equilibrium: the female ballet dancers' experience

Objective: To analyse the interaction between visual restrictions and somatosensory disturbances on unipedal control equilibrium with or without classical dance training. Methods: The support (computerized force platform) was disturbed during roll and pitch sways in association with restriction of the left and right visual hemifields (selective nasal and temporal hemiretina goggles). The effect of training by comparing spontaneous dynamic equilibrium (spectral analysis of body sways) between 14 healthy female right-sided untrained and expert dancers was assessed. The foot of the supporting leg was placed on the unstable platform center in the same way for all the participants. Results: In pitch sways, analysis of variance showed that, regardless of the supporting leg used, dancers oscillated significantly less than untrained participants (p<0.01). Furthermore, all participants were significantly less stable in pitch sways if the left visual field was occluded (p<0.001). However, in roll sways, equilibrium was disturbed by covering the eyes only in dancers (p<0.001). Conclusion: When classical dancers' feet were in an unusual position during the experimental task (a somatosensory constraint for them but not for untrained participants), dancers shifted their spatial reference frame from somesthetic to visual cues. The elimination of this visual reference may have created imbalance, indicating that right hemispheric visual dominance is particularly useful for postural control in complex equilibrium conditions.