Research Article Laterality of Stance during Optic Flow Stimulation in Male and Female Young Adults Michela Persiani, Alessandro Piras, Salvatore Squatrito, and Milena Raffi Department of Biomedical and Neuromotor Sciences, University of Bologna, 40126 Bologna, Italy Correspondence should be addressed to Milena Raf; milena.raf@unibo.it Received 21 November 2014; Accepted 8 April 2015 Academic Editor: J´ ulia M. Greve Copyright © 2015 Michela Persiani et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. During self-motion, the spatial and temporal properties of the optic fow input directly infuence the body sway. Men and women have anatomical and biomechanical diferences that infuence the postural control during visual stimulation. Given that recent fndings suggest a peculiar role of each leg in the postural control of the two genders, we investigated whether the body sway during optic fow perturbances is lateralized and whether anteroposterior and mediolateral components of specifc center of pressure (COP) parameters of the right and lef legs difer, reexamining a previous experiment (Raf et al. (2014)) performed with two, side-by-side, force plates. Experiments were performed on 24 right-handed and right-footed young subjects. We analyzed fve measures related to the COP of each foot and global data: anteroposterior and mediolateral range of oscillation, anteroposterior and mediolateral COP velocity, and sway area. Results showed that men consistently had larger COP parameters than women. Te values of the COP parameters were correlated between the two feet only in the mediolateral axis of women. Tese fndings suggest that optic fow stimulation causes asymmetry in postural balance and diferent lateralization of postural controls in men and women. 1. Introduction Te human upright stance is characterized by continuous movements of the body similar to an inverted pendulum [1]. Vision provides the nervous system with information regard- ing the position and movements of elements present in the environment relatively to the body, playing an important role in the postural stabilization. Te characteristic pattern of visual stimuli that provides information of self-motion and the environmental structure is defned as “optic fow” [2, 3]. Te optic fow originates from the focus of expansion (FOE), a point of the visual scene that corresponds to the fnal destination of self-motion. Te neural mechanisms integrate visual, vestibular, and proprioceptive inputs of self-motion perception to generate the typical body oscillation defned as body sway. Te body sway is regulated by the neuromotor system and is considered a consequence of small postural oscillations. Tese small postural oscillations refect the reg- ulatory activity of the several control loops of stabilization of an unstable structure, such as the human body, for mainte- nance of balance [4, 5]. Until now, several studies have focused on the mainte- nance of balance control, looking at the variation of the center of pressure (COP) trajectory. Te COP analysis with bilateral force plate can be useful for assessing postural behavior related to each foot in healthy individuals [6, 7]. Few studies have addressed the laterality or asymmetry during quiet stance; however, these studies were performed with the eyes open or closed or under two-dimensional visual stimulation [8–10]. In a previous paper, we showed that foveal, peripheral, and full feld optic fow stimulations evoke diferent muscular activations in the right and lef leg and diferent directions of oscillation in men and women [11]. Tus, the aim of this paper was to verify whether the diferent oscillations caused by foveal, peripheral, and full feld optic fows depend on the variations of specifc COP parameters in each leg. Results showed that optic fow signifcantly afected the COP Hindawi Publishing Corporation BioMed Research International Volume 2015, Article ID 542645, 9 pages http://dx.doi.org/10.1155/2015/542645