This competitive revision application to grant R01AG029546 is submitted in response to NOT-OD-09-058: NIH Announces the Availability of Recovery Act Funds for Competitive Revision Applications. This revision proposes to add optical brain imaging to our ongoing study that will enable us to visualize and quantify cortical brain activity while young and elderly adults perform our current balance and information processing (IP) tasks. No change in experimental protocol is required to add this neuroimaging aim to our current study. Falls are a leading cause of injury and death among the elderly, resulting from a complex interaction of sensory, motor and cognitive loss. Older adults have been shown to require increased cognitive resources (i.e. attention) for balance, and environmental changes that alter sensory information about body orientation and motion have a greater impact on balance of older adults compared to young adults. Currently, it is not known to what extent differences in postural control between young and older adults are due to differences in sensory integration. Moreover, the interaction of attention and sensory integration in older adults has not been fully studied or developed. Our current research is providing insights into these issues through dual-task experiments involving moderate balance perturbations and IP tasks, the data from which is then fit to a postural control model. A central hypothesis of our research is that attention-requiring information processing tasks concurrent with moderate postural challenges will divert attention away from balance control in older adults, which can be quantified by time delay and other physiologically relevant parameters in our model. The proposed addition of neuroimaging using a portable, non-invasive optical imaging system to measure cortical brain activation while subjects perform the dual task experiments, will allow us to better address the cognitive basis of interference in postural control between balance and attention. Our hypothesis is that this interference will manifest as a larger recruitment of activation areas from the midfrontal and dorsolateral prefrontal brain regions and show diminished activation in the premotor and motor regions. We expect that this effect will be modulated by IP task difficulty and that this effect will be greater in older subjects. PUBLIC HEALTH RELEVANCE: The proposed research is relevant to public health in that falls are a significant problem in older adults compared to young adults. Environmental changes that alter sensory orientation information tend to have a greater destabilizing effect on older adults, and older adults appear to require greater attentional resources for balance control. Our research will provide new insights into the interaction of balance and attention through cortical brain imaging while subjects perform balance and attention tasks simultaneously.