Multimodal Imaging of Brain Activity to Investigate Walking and Mobility Decline in Older Adults (Mind in Motion Study): Hypothesis, Theory, and Methods

Abstract

Age-related brain changes likely contribute to mobility impairments, but the specific mechanisms are poorly understood. Current brain measurement approaches (e.g., functional magnetic resonance imaging (fMRI), functional near infrared spectroscopy (fNIRS), PET) are limited by inability to measure activity from the whole brain during walking. The Mind in Motion Study will use cutting edge, mobile, high-density electroencephalography (EEG). This approach relies upon innovative hardware and software to deliver three-dimensional localization of active cortical and subcortical regions with good spatial and temporal resolution during walking. Our overarching objective is to determine age-related changes in the central neural control of walking and correlate these findings with a comprehensive set of mobility outcomes (clinic-based, complex walking, and community mobility measures). Our hypothesis is that age-related walking deficits are explained in part by the Compensation Related Utilization of Neural Circuits Hypothesis (CRUNCH). CRUNCH is a well-supported model that describes the over-recruitment of brain regions exhibited by older adults in comparison to young adults, even at low levels of task complexity. CRUNCH also describes the limited brain reserve resources available with aging. These factors cause older adults to quickly reach a ceiling in brain resources when performing tasks of increasing complexity, leading to poor performance. Two hundred older adults and twenty young adults will undergo extensive baseline neuroimaging and walking assessments. Older adults will subsequently be followed for up to 3 years. Aim 1 will evaluate whether brain activity during actual walking explains mobility decline. Cross sectional and longitudinal designs will be used to study whether poorer walking performance and steeper trajectories

Brain activity during walking in older adults: Implications for compensatory versus dysfunctional accounts

“…However, by increasing the obstacles incrementally, accompanying changes in brain activity can be assessed, coupled with changes in walking performance, so that potential compensatory brain activity and its limitations can be identified. This methodology has been applied successfully in older adults in many cognitive experiments (Cappell et al, 2010;Carp et al, 2010;Reuter-Lorenz & Cappell, 2008), and has recently been investigated in walking (Clark et al, 2019). 2) Terrain modification paradigms are promising for studying how the neural control of mobility changes with age.…”

Cortical Engagement Metrics During Reactive Balance Are Associated With Distinct Aspects of Balance Behavior in Older Adults

“…Older adults show greater prefrontal cortical activity during a wide range of motor tasks, including interlimb coordination tasks (Heuninckx et al, 2008) and steady-state walking (Chen et al, 2017;Mirelman et al, 2017;Hawkins et al, 2018). Whether age-related differences in prefrontal cortical activity play a beneficial (i.e., compensatory; Clark et al, 2019) or detrimental (i.e., age-related neural dedifferentiation; Payer et al, 2006;Gagnon et al, 2019) role in motor function in older adults remains controversial (for review see Seidler et al, 2010) and may depend on the context and challenge of the motor task (e.g., level of complexity and difficulty; Clark, 2015). In contrast to younger adults, older adults utilize motor control strategies that require higher levels of cognitive processing, which are effective at slower speeds but less effective during fast speed motor performance (Boisgontier and Nougier, 2013).…”

Prefrontal-motor and somatosensory-motor cortical network interactions during reactive balance are associated with distinct aspects of balance behavior in older adults

“…Whether age-related differences in prefrontal cortical activity play a beneficial (i.e. compensatory) (Clark et al, 2019) or detrimental (i.e. agerelated neural dedifferentiation) (Gagnon et al, 2019;Payer et al, 2006) role in motor function in older adults remains controversial (for review see R. D. Seidler et al, 2010) and may depend on the context and challenge of the motor task (e.g.…”