This study examines differences in reactive stepping responses between older adults with mild cognitive
impairment and cognitively intact older adults when exposed to novel and repeated gait-trip perturbations. Falls
occur in >30% of older adults each year, most often due to trips, and lead to ~2.8 million hospital admissions,
32,000 deaths, and $50 billion in medical costs. Fall incidence is doubled in older adults with mild cognitive
impairment (OAwMCI), which is a prodromal stage of dementia that affects about 17% of the aging population.
Substantial evidence indicates that OAwMCI have impaired volitional balance control and gait compared to
cognitively intact older adults (CIOA); however, the underlying mechanisms that explain why OAwMCI have a
greater predisposition to falls are yet to be investigated. The main causative factors of falling have been identified
as deficits in reactive balance control, including reduced center of mass (COM) stability and insufficient vertical
limb support post-perturbation, which could be associated with impaired neuromuscular coordination (reduced
muscle synergies). Further, evidence from mobile neuroimaging techniques such as electroencephalography
(EEG) suggest the role of the cortex in generating a reactive stepping response, as indicated by perturbation-
evoked potentials (e.g., N1) and increase in beta frequency power when exposed to unpredicted perturbations.
However, it is unknown how the pathology related to MCI (structural neural damage, reduced sensorimotor
integration) affects reactive balance responses. Further, it is unknown if OAwMCI are capable of improving their
reactive balance through repeated perturbations. Perturbation training has been introduced as a novel fall
prevention paradigm involving repeated exposure to simulated balance disturbances (e.g., slips, trips), with
robust effects on laboratory and real-life fall reduction. Trial-by-trial analyses indicate that CIOA can acquire
motor adaptations in as little as 5 perturbation exposures, including improvements in biomechanical outcomes
(fall rate, COM stability) and enhanced neuromuscular control (increased muscle synergy number). In theory,
perturbation training could be implemented in OAwMCI to mitigate increased fall risk, however it is first necessary
to assess 1) the magnitude of reactive balance impairment, and 2) the ability to acquire motor adaptations to
repeated perturbations in this population. Thus, we propose a mechanistic investigation to determine differences
in the biomechanical, neuromuscular, and cortical control of reactive balance between OAwMCI and CIOA when
exposed to a novel treadmill gait-trip (Aims 1&2). We will also examine differences in the rate and magnitude of
motor adaptation between OAwMCI and CIOA when exposed to 8 repeated treadmill gait-trips (Aim 3). The
clinical impact of this study will be to mechanistically understand how pathology related to MCI may contribute
to balance impairment and increased fall-risk. Further, with an understanding of how OAwMCI are able to adapt
to repeated perturbations, this study will pave the road for the future design of effective perturbation training
protocols that could significantly improve balance control and reduce fall incidence in OAwMCI.