Network segregation mediates the association between motor imagery fMRI and walking function
Poster No:
1167
Submission Type:
Abstract Submission
Authors:
Sumire Sato1, Valay Shah1, Grant Tays1, David Clark1, Daniel Ferris1, Chris Hass1, Todd Manini1, Rachael Seidler1
Institutions:
1University of Florida, Gainesville, FL
First Author:
Co-Author(s):
Introduction:
Functional magnetic resonance imaging (fMRI) during imagined walking in older adults has shown increased recruitment in the premotor cortex and hippocampus compared to younger adults[1, 2]. These brain regions are key projection areas from the vestibular cortex, which show structural declines in aging[3]. Resting state functional connectivity is associated with task-based fMRI activity during cognitive tasks[4, 5]. Investigating the role of vestibular resting state brain activity on the association between motor imagery fMRI and function may help better understand how the brain activates in response to task demands. The objective of this study was to examine the mediation effect of vestibular resting state network segregation on the relationship between imaginary walking fMRI brain activation and walking function.
Methods:
20 typical younger adults (Age: 23 ± 3.5 yrs) and 36 typical older adults (Age: 75 ± 6.4 yrs) participated in this study (Full exclusion/inclusion criteria in [6]). Self-selected walking speed was assessed with a 400m walk. Brain images were collected using a Siemens Prisma 3T scanner with a 64-channel head coil. Structural T1-weighted images were collected using a magnetization-prepared rapid gradient echo sequence. fMRI scans were collected using a multiband, interleaved echo planar imaging sequence. During the motor imagery fMRI scan, participants were shown pictures of four conditions of uneven terrains with colored disks on which they had walked previously (For details, see [7]), and were instructed to imagine themselves walking on the treadmill belts (Figure 1A). Standard preprocessing steps were followed for structural and fMRI images[8]. For task-based fMRI, spherical ROIs were created from [1] and [2] for the left and right premotor cortex and left and right hippocampus. First-level contrasts (task > rest) were used to extract mean beta values from the ROIs. For resting state connectivity analysis we identified vestibular seed regions from a meta-analysis[9]. We quantified left and right vestibular network segregation as the difference of the mean within-network connectivity and the mean between-network connectivity divided by the mean within-network connectivity[10]. Group and terrain differences in motor imagery brain activation were assessed through one-way ANCOVA (covariate = biological sex). The relationship between vestibular network segregation and motor imagery brain activation was assessed with a partial correlation. For the pairs of variables that demonstrated a significant relationship, we assessed mediation of vestibular network segregation on the association between motor imagery brain activation and walking function. Statistical significance was established with an alpha level = 0.05.
Results:
We found no significant Group, Terrain, or Group x Terrain interaction effect for left and right hippocampus and left and right premotor brain activation during motor imagery (Figure 1B; all p-values > 0.05). We performed three mediation analyses based on the correlations found between motor imagery brain activity and resting state vestibular network segregation (Figure 2A), with walking speed as the dependent variable. Left vestibular network segregation mediated (1) the effect of left premotor activation during medium level terrain on walking speed and (2) right premotor activation during medium level terrain on walking speed. (3) Left premotor activation during medium level terrain showed a significant total effect on walking speed, but mediation effect of right vestibular network segregation was not significant (See Figure 2B and 2C for detailed statistical output).
Conclusions:
Left vestibular network segregation may be especially important for age differences in brain activation in the premotor cortex that is associated with walking. Identifying the role of resting state network connectivity may be a promising biomarker to assess age differences in brain activation when individuals walk with different task demands.
Higher Cognitive Functions:
Imagery
Lifespan Development:
Aging 1
Modeling and Analysis Methods:
Activation (eg. BOLD task-fMRI) 2
Connectivity (eg. functional, effective, structural)
Motor Behavior:
Motor Planning and Execution
Keywords:
ADULTS
Aging
FUNCTIONAL MRI
Motor
MRI
Physical Therapy
Other - Vestibular, Motor imagery, walking
1|2Indicates the priority used for review
Provide references using author date format
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