Locomotor Adaptability for Community Mobility of Older Adults: The Role of Gait Automaticity

Summary

The investigators will test the following: 1) the extent of locomotor adaptation improvement in individuals aged 65 years and older; 2) the association between initial walking automaticity (i.e. less PFC activity while walking with a cognitive load) and prefrontal-subcortical function (measured via neuropsychological testing); and 3) whether improvements in locomotor adaptability result in improvements in the Functional Gait Assessment (FGA), a clinically relevant indicator of dynamic balance and mobility in older adults. To answer these questions, the investigators will combine innovative techniques from multiple laboratories at the University of Pittsburgh. Automatic motor control (Dr. Rosso's expertise) will be assessed by wireless functional near-infrared spectroscopy (fNIRS) of the PFC during challenged walking conditions (walking on an uneven surface and walking while reciting every other letter of the alphabet). fNIRS allows for real-time assessment of cortical activity while a participant is upright and moving by way of light-based measurements of changes in oxygenated and deoxygenated hemoglobin. Locomotor adaptation (Dr. Torres-Oviedo's expertise) will be evaluated with a split-belt walking protocol (i.e., legs moving at different speeds) that the investigators and others have used to robustly quantify motor adaptation capacity in older individuals and have shown to be reliant on cerebellar and basal ganglia function. The investigators will focus on two important aspects of locomotor adaptation that the investigators have quantified before: (Aim 1) rate at which individuals adapt to the new (split) walking environment and (Aim 2) capacity to transition between distinct walking patterns (i.e., the split-belt and the overground walking patterns), defined as motor switching. Adaptation rate and motor switching are quantified using step length asymmetry, which is the difference between a step length taken with one leg vs. the other. The investigators will focus on this gait parameter because it robustly characterizes gait adaptation evoked by split-belt walking protocols. Finally, the investigators will quantify participant's cognitive function (Dr. Weinstein's expertise) through neuropsychological battery sensitive to prefrontal-subcortical function. The investigators will mainly focus on evaluating 1) learning capacity reliant on cerebellar structures and 2) assessing executive function heavily reliant on PFC and, to a lesser extent, the basal ganglia.

Description

Eligibility

Age range

19+ years

Sex

All

Healthy volunteers

Yes

Interventions

• Other
  Split-belt walking

  These will be used in all experiments and consists of a time period during which the legs move at different speeds (0.5 m/s vs. 1 m/s). The investigators select those speeds since the investigators have observed in our preliminary data and published study (Sombric et al. 2017) that older individuals adapted at these speeds exhibit large deficits at motor switching when transitioning to overground walking. This large reference signal will facilitate the detection of a change in motor switching (Aim 2) following the Intervention.

• Other
  Multiple transitions between split-belt and tied-belt walking

  This intervention consists of multiple short adaptation blocks (i.e., 6 blocks of 200 strides each) interleaved with short de-adaptation blocks (i.e., 5 blocks of 200 strides of tied-belt walking each). It was designed based on several studies showing improvements in adaptation rate in young adults with a similar protocol (Malone et al. 2011; Day et al. 2018; Leech et al. 2018).

Location