Hindawi Publishing Corporation Rehabilitation Research and Practice Volume 2013, Article ID 890962, 7 pages http://dx.doi.org/10.1155/2013/890962 Clinical Study Immediate Beneficial Effects of Mental Rotation Using Foot Stimuli on Upright Postural Stability in Healthy Participants Tsubasa Kawasaki and Takahiro Higuchi Department of Health Promotion Science, Graduate School of Human Health Science, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo 192-0397, Japan Correspondence should be addressed to Takahiro Higuchi; higuchit@tmu.ac.jp Received 4 September 2013; Accepted 5 December 2013 Academic Editor: Francois Prince Copyright © 2013 T. Kawasaki and T. Higuchi. 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. Te present study was designed to investigate whether an intervention during which participants were involved in mental rotation (MR) of a foot stimulus would have immediate benefcial efects on postural stability (Experiment 1) and to confrm whether it was the involvement of MR of the foot, rather than simply viewing foot stimuli, that could improve postural stability (Experiment 2). Two diferent groups of participants ( = 16 in each group) performed MR intervention of foot stimuli in each of the two experiments. Pre- and postmeasurements of postural stability during unipedal and bipedal standing were made using a force plate for the intervention. Consistently, postural sway values for unipedal standing, but not for bipedal standing, were decreased immediately afer the MR intervention using the foot stimuli. Such benefcial efects were not observed afer the MR intervention using car stimuli (Experiment 1) or when participants observed the same foot stimuli during a simple reaction task (Experiment 2). Tese fndings suggest that the MR intervention using the foot stimuli could contribute to improving postural stability, at least when it was measured immediately afer the intervention, under a challenging standing condition (i.e., unipedal standing). 1. Introduction A mental rotation (MR) task using a visual stimulus of a pictured body part, typically a hand or foot, asks participants to judge whether the stimulus is the right or lef hand/foot (i.e., laterality judgment). Te time required for judging (i.e., reaction time) increased as the linear function of angle rotation [1, 2]. Even if a stimulus was presented with no rotation, the reaction time was delayed when participants kept their right hand behind their back so that the orientation of the hand was far from that of the stimulus [3]. Te reaction time was nearly equivalent to the time of the actual body movement to the orientation of the stimulus; for example, the reaction time at 90 degrees is similar to the time it would actually take to move the hand 90 degrees [2]. Moreover, neuroimaging studies showed that the brain regions in the posterior parietal cortex and the precentral cortex, which are involved in motor planning [4, 5], were activated while performing the MR of body parts [6, 7]. Based on these fndings, it has been generally considered that MR ofa body part involves cognitive processes used for both motor imagery and motor execution [1, 2, 8]. Te present study was designed to investigate with two experiments whether the intervention during which partici- pants were involved in MR of the foot would have immediate benefcial efects on postural stability. If MR of a body part involves cognitive processes used for both motor imagery and motor execution, then repeated MR for a certain period of time might activate such cognitive processes and, as a result, contribute to improving motor performance. In fact, our previous study showed that interventions that involved participants in motor imagery [9] and motor execution [10] of a body part had immediate benefcial efects on postural stability during upright unipedal standing [9, 10]. We investigated whether a similar efect would be observed when MR, instead of motor imagery, was used for intervention. In the present study, a foot stimulus was selected as the body part to be used in MR based on the foot’s essential