Sensorimotor processing and body motion perception

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Human upright balance is inherently unstable. To maintain balance, information from various sensors are combined; each sensory cue provides valuable information on body sway. Although balance control is possible with a single sensory cue, balance control is best when all sensory cues are processed. To assess the role of each sensory cue, it is common to experimentally induce sensory illusion. The first aim of this research program is to assess the balance control threshold to a vestibular or a visual stimulation. To pursuit this aim, we will alter vestibular or visual information. During normal upright standing, acceleration acting on the head are detected by the vestibular system. Contribution of the vestibular system to balance control can be evaluated by applying a small current through the ears. Thus, small current will be applied while participants will be standing. To determine the balance control threshold to a visual stimulation, participants will look at a large screen displaying rotating dots. Balance control threshold will be determined using advanced signal processing techniques. The visual system plays an important role in helping to maintain human balance as visual cues provide information about unintended body sway. In daily life, when one stands still, it is possible that the velocity of the visual surround does not represent his/her body motion. In such a situation, the brain needs to detect if visual information relates to body motion or to the environment. The second aim of this proposal will be to determine the contribution of vestibular cues to a visual evoked postural response. To do so, we will create the illusion that the body is moving faster than it is. Creating sensory mismatch will allow us to assess how the brain uses sensory information to body sway during visual stimulation. Many studies have reported improvement in balance control during sensory augmentation (SA). SA is the delivery of additional sensory cues, e.g. via tactile information, that convey pertinent information about body sways. Limited studies, however, have investigated the underlying neural mechanisms of its effectiveness. To address this gap in the literature, we will record brain activity through electroencephalography (EEG) while participants control their balance and receive SA. By comparing brain activity during balance control with and without SA, we will quantify the change in brain activity related to SA. This will allow us to determine the effectiveness of SA on brain activity and balance control improvement. Overall, this research program will provide important fundamental knowledge regarding the underlying mechanisms involved in balance control and body motion perception. Further, this work can contribute to the advancement of sensory interface for prosthesis users, the development of navigation devices or sensors to enhance robots balance control.