Supplementary Material for: Brain Structural Correlates of Obstacle Negotiation in Mild Cognitive Impairment: Results from The Gait and Brain Study

Introduction- Mild Cognitive Impairment (MCI) affects obstacle negotiation capabilities, potentially increasing the risk of falls in older adults. However, it is unclear whether smaller brain volumes typically observed in older individuals with MCI are related to the observed hazardous obstacle negotiation in this population. Methods- A total of 93 participants (71.9±5.36years of age; MCI=53 / Control=40) from the Gait and Brain Study were analyzed. Gray matter (GM) volumes from the frontal, temporal and parietal lobes were entered in the analysis. Gait performance was recorded using a 6-m electronic walkway during two cognitive load conditions while approaching and stepping over an obstacle: 1) single-task; 2) while counting backwards by 1s from 100 (dual-task). Anticipatory adjustments in gait performance to cross an “ad hoc” obstacle were electronically measured during pre-crossing phases: early(3 steps before the late phase) and late(3 steps before obstacle). Association between the percentage of change in average gait speed and step length from early to late (i.e. anticipatory adjustments) and GM volumes were investigated using multivariate models adjusted for potential confounders. Results- Anticipatory adjustments in gait speed (Wilks’ lambda .35; eta2 .64; p=.01) and step length (Wilks’ lambda .33; eta2 .66; p=.01) during dual-task condition were globally associated with GM volumes in MCI. Individuals with MCI with smaller GM volumes in the left inferior frontal gyrus, left hippocampus, right hippocampus and right entorhinal cortex made significantly fewer anticipatory gait adjustments prior to crossing the obstacle. Discussion/Conclusion- Frontotemporal atrophy may affect obstacle negotiation capabilities potentially increasing the risk of falls in MCI.