Given the cognitive decline and poor reactive responses among OAwMCI, it is essential to incorporate a strategy to enhance cognition and motor performance for promoting healthy aging. For this reason, we propose this study that aims to determine the feasibility, applicability and tolerability of a dual-task perturbation training paradigm in OAwMCI. This involves a treadmill induced perturbation training while concurrently performing a cognitive task with an aim to improve effective compensatory stepping strategies to prevent balance loss. Further, while testing on laboratory induced perturbations may provide an insight into understanding kinematic variables, evaluating the change on performance-based outcome measure may be clinically useful. The overall aim of this proposal to examine the central mechanisms of reactive balance control and perturbation-training adaptation to improve fall-resisting skills in healthy older adults and people with MCI using the following set of aims. Aim 1: To examine biomechanical and neuromuscular differences during reactive balance control against mechanical perturbations during stance and gait between OAwMCI and CIOA. Compared to CIOA, OAwMCI will show: H1.1. greater falls due to impaired biomechanical (delayed step initiation, lower reactive stability and greater limb support descent) and neuromuscular responses (longer postural response latencies and fewer muscle synergies with different structural activation) on novel stance and gait perturbations, which will worsen with dual task performance; H1.2. reduced modulation (scaling) of biomechanical and neuromuscular responses with increasing perturbation intensity; H1.3. slower rate of adaptation in stability control and muscle synergy adjustment with repeated perturbation exposure.

Aim 2: To relate impairments observed during reactive balance control in perturbed stance and gait with structural brain integrity, cognition and falls in OAwMCI. These older adults will display H2.1: Lower gray matter volume in fronto-pareital cortex and brainstem, and lower white matter integrity in sensorimotor pathways which will significantly correlate with poor performance on reactive stepping response; H2.2: Lower scores on neuropsychological battery test and NIH cognitive toolbox examining domains of executive function (attention, cognitive flexibility and response inhibition), visuo-spatial awareness, episodic memory which will correlate with deteriorated reactive stepping response. H2.3: Fall-Index computed from measures of reactive stability and limb support that are obtained from perturbation-based reactive measures will better discriminate prospective laboratory induced and real-life falls than conventional instrumented (postural sway and limits of stability) and performance-based clinical measures of balance and mobility, with increased predictive accuracy of Fall-Index under dual-task conditions.

Aim 2: To determine if deficits in reactive balance responses contribute to increased falls in OAwMCI during static and dynamic tasks than CIOA especially under dual-tasking. H2.1: Measures of reactive stability and limb support under dual-task conditions during perturbed gait will best discriminate retrospective and laboratory induced falls in this population. H2.2 Predictive accuracy of Fall-Index which will be greater than of clinical measures of balance and mobility.

Aim 3: To examine the feasibility and potential effectiveness of novel 6-week perturbation-based cognitive-motor intervention for improving fall-resisting skills during perturbed stance and gait. H3.1: Post-training OAwMCI will improve stability control, cognition and reduced laboratory falls, especially under dual-task conditions. H3.2: Baseline cognition and structural brain integrity/connectivity will predict change in stability control and fall-risk. H3.3. Improvements in stability control, cognition and falls reduction will be retained for at least 3 months post withdrawal of intervention resulting in improved community ambulation and reduced fear of falling and perceived cognitive load on activities of daily living