Saccades horizontal or vertical at near or at far do not deteriorate postural control.
OBJECTIVE
There is a discrepancy about the effect of saccades on postural control: some studies reported a stabilization effect, other studies the opposite. Perturbation of posture by saccades could be related to loss of vision during saccades (saccades suppression) due to high velocity retinal slip. On the other hand, efferent and afferent proprioceptive signals related to saccades can be used for obtaining spatial stability over saccades and maintaining good postural control. In natural conditions saccades can be horizontal, vertical and made at different distance. The present study examines all these parameters to provide a more complete view on the role of saccade on postural control in quiet stance.


METHODS
Horizontal or vertical saccades of 30 degrees were made at 1Hz and at two distances, 40 and 200cm. Eye movements were recorded with video-oculograhpy (EyeLink II). Posturography was recorded with the TechnoConcept platform. The results from "saccade" conditions are compared to "fixation control" condition (at far and near).


RESULTS
The video oculography results show that subjects performed the fixation or the saccade task correctly. Execution of saccades (horizontal or vertical at near or at far distance) had no significant effect on the surface of center of pressure (CoP), neither on the standard deviation of the lateral body sway, nor on the variance of speed of the CoP. Moreover, whatever the distance, execution of saccades decreased significantly the standard deviation of the antero-posterior sway.


CONCLUSIONS
We conclude that saccades, of either the direction and at either the distance, do not deteriorate postural control; rather they could reduce sway. Efferent and proprioceptive oculomotor signals as well as attention could contribute to maintain or improve postural stability while making saccades.
Rey
Frederic
F
IRIS Group, Laboratoire de Physiologie de la Perception et de l'Action (LPPA), UMR 7152, CNRS, Collège de France 11, place M. Berthelot, 75005 Paris, France.
Lê
Thanh-Thuan
TT
Bertin
René
R
Kapoula
Zoï
Z
D000328:Adult; D006801:Humans; D011187:Posture / Q000502:physiology*; D011434:Proprioception / Q000502:physiology; D012438:Saccades / Q000502:physiology*; D014741:Video Recording