Mechanisms of Stochastic Resonance in Human Postural Control

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The complex task of stabilizing the body in an upright position is critical for performing many daily activities and avoiding falls. In spite of this importance, balance control is still not fully understood. Recently, a phenomenon called stochastic resonance has been used to gain insights into and enhance balance control during standing. It describes a mechanism that uses noise to improve the detection and transmission of weak signals in various systems. Stochastic resonance is based on the concept that the flow of information through a system can be maximized by an optimal level of noise. While the effect of such noise on the sensory system has been documented, it is unclear to what degree its benefits extend to processes within the brain. Accordingly, it is possible that improved balance control in the presence of sensory noise is a result not only of better signal detection, but also of increased activity in higher brain areas.**Building upon my experience in balance control, the long-term objective of this research program is to understand the central and peripheral mechanisms that are responsible for postural improvements via sensory noise. To reach this goal, the first objective is to deliver mechanistic evidence for the effect of sensory noise on speed of processing, a key factor of balance control. We will use a simple reaction time task to determine the relationship between noise-evoked changes in reaction times and various states of brain activity. The second objective is to identify physiological and behavioural factors of reactive balance control that are changed by sensory noise. In contrast to quiet upright standing, a perturbed standing paradigm will allow us to isolate noise-enhanced activity at both the sensory and motor stages of central processing. In addition, insights from reactive balance control will provide a good scientific basis for developing interventions that reduce balance impairments via sensory noise. In both lines of research, noise-evoked changes will be captured by physiological and behavioural measures (brain and muscle activity, arousal, etc.).**The effect of sensory noise on quiet upright standing has been documented. However, our understanding of its impact on functionally more relevant tasks such as reactive balance control is limited. At the same time, it is unclear if noise-induced changes are linked to increased activity of higher brain areas. To address these shortfalls, we will characterize the influence of sensory noise on speed of processing and other factors of reactive balance control. We expect to make important contributions in the area of human systems and functions. First, we will determine whether reaction times can be reduced via sensory noise and how a potential effect depends on internal noise within the brain. Second, changes to the activity in certain brain areas will indicate that sensory noise does not only enhance sensory detection, but also central processing associated with the execution of a balance response. Finally, we will characterize effects of sensory noise on reactive postural control in dependence of the noise modality and its involvement in the recovery task. While the expected contributions are fundamental in nature, they will also have important implications for applied fields such as human health and performance. For example, the intended comparison between young and elderly individuals will serve as an ideal stepping stone for mechanistically informed studies that use sensory noise to reduce fall risk in elderly Canadians. Highly qualified personnel will be trained in a multidisciplinary environment to build capacity for future challenges of our health care system.