Imaging gait analysis: An fMRI dual task study

Abstract

Introduction: In geriatric clinical diagnostics, gait analysis with cognitive-motor dual tasking is used to predict fall risk and cognitive decline. To date, the neural correlates of cognitive-motor dual tasking processes are not fully understood. To investigate these underlying neural mechanisms, we designed an fMRI paradigm to reproduce the gait analysis.

Methods: We tested the fMRI paradigm's feasibility in a substudy with fifteen young adults and assessed 31 healthy older adults in the main study. First, gait speed and variability were quantified using the GAITRite^© electronic walkway. Then, participants lying in the MRI-scanner were stepping on pedals of an MRI-compatible stepping device used to imitate gait during functional imaging. In each session, participants performed cognitive and motor single tasks as well as cognitive-motor dual tasks.

Results: Behavioral results showed that the parameters of both gait analyses, GAITRite^© and fMRI, were significantly positively correlated. FMRI results revealed significantly reduced brain activation during dual task compared to single task conditions. Functional ROI analysis showed that activation in the superior parietal lobe (SPL) decreased less from single to dual task condition than activation in primary motor cortex and in supplementary motor areas. Moreover, SPL activation was increased during dual tasks in subjects exhibiting lower stepping speed and lower executive control.

Conclusion: We were able to simulate walking during functional imaging with valid results that reproduce those from the GAITRite^© gait analysis. On the neural level, SPL seems to play a crucial role in cognitive-motor dual tasking and to be linked to divided attention processes, particularly when motor activity is involved.

Keywords: cognitive aging; cognitive‐motor dual tasking; fall risk; geriatric clinical diagnostics; superior parietal lobe.

Figure 1

(a) GAITRite^© electronic walkway system with embedded pressure sensors which register the walking parameters. (b) MRI‐compatible stepping device, stepping parameters are recorded by response pads. (c) Positive and mainly significant correlations between the total number of correct responses of the GAITRite^© and the fMRI gait analysis. (d) Positive and significant correlations between walking or stepping speed in sec of the GAITRite^© and the fMRI gait analysis. (e) Mean and SE percent dual task costs. The dual task costs were significantly larger for motor variability than for motor speed and cognitive performance; this was true for both gait analyses. VF = verbal fluency; SS = serial subtraction; ***p < .001; **p < .01; *p < .05; + p < .1

Figure 2

Group activation maps rendered onto sagittal and transversal group average brain slices (A = anterior, P = posterior, L = left, R = right; x, z = TAL coordinates). Group contrast t value maps of task versus baseline for motor single task, serial subtraction (SS) single task and SS dual task. Similar activation maps were found for the verbal fluency single and dual task. ROIs: primary motor cortex (M1), supplementary motor area (SMA), cingulate motor area (CMA), superior parietal lobe (SPL)

Figure 3

Individual activation maps rendered onto coronal, sagittal and transversal individual brain slices (L = left, R = right, A = anterior, P = posterior; x, y, z = TAL coordinates). Single subject contrast t value maps of task versus baseline for motor single task, serial subtraction (SS) single task and SS dual task. ROIs: primary motor cortex (M1), supplementary motor area (SMA), cingulate motor area (CMA), superior parietal lobe (SPL)

Figure 4

Data from younger adults in the left panels and from older adults in the right panels. (a) Percent occurrence of the ROI fMRI activation per task condition. ROIs: primary motor cortex (M1) for feet or tongue representation, supplementary motor area and cingulate motor area (SMA/CMA), superior parietal lobe (SPL). (b) Mean and SE t values of the fMRI activation per ROI of the contrast task versus baseline. The t values for the cognitive single tasks and the dual tasks are merged. (c) Mean and SE percent dual task costs: (single task – dual task)/single task × 100. The dual task costs are significantly lower for SPL than for the other ROIs. VF = verbal fluency; SS = serial subtraction

Figure 5

(a) Individual coordinates of the SPL ROI plotted on coronal (left) and transversal (right) group average brain slices. (b) Significant positive correlations between SPL t values and fMRI stepping coefficient of variation (CV) or mean cycle time for motor single task or merged dual tasks, respectively. (c) Significant positive correlations between percent dual task costs for SPL t values ((dual task – single task)/single task × 100) and percent switching costs in TMT ((B‐A)/A × 100). VF = verbal fluency; SS = serial subtraction; *p < .05