Sensorimotor and Frontoparietal Network Connectivity Are Associated With Subsequent Maintenance of Gait Speed and Episodic Memory in Older Adults.

BACKGROUND: Slow gait is predictive of functional impairments in older adults, while concomitant slow gait and cognitive complaints are associated with a greater risk for cognitive decline and dementia. However, functional neural correlates for gait speed maintenance are unclear. As the sensorimotor network (SMN) and frontoparietal network (FPN) are integral components of these functions, this study investigated differences in SMN and FPN in older adults with/without gait speed decline over 24 months; and whether these networks were associated with the maintenance of cognitive function. METHODS: We included 42 community-dwelling older adults aged >70 years from the MOBILIZE Boston Study. Resting-state fMRI was performed at the study baseline. Participant characteristics, gait speed, Mini-Mental State Examination, and Hopkins Verbal Learning Test (HVLT) were assessed at baseline and at 24-month follow-up. Decliners were identified as individuals with >0.05 meters/second decline in gait speed from baseline to 24 months. Of the 26 decliners and 16 maintainers, decliners exhibited a significant decline in delayed-recall performance on the HVLT over 24 months. RESULTS: Controlling for baseline age and multiple comparisons, contrary to initial hypothesis, maintainers exhibited lower baseline primary motor and premotor connectivity (p = .01) within the SMN, and greater baseline ventral visual-supramarginal gyrus connectivity within the FPN (p = .02) compared to decliners. Lower primary motor-premotor connectivity was correlated with maintenance of delayed-recall performance on the HVLT (p = .04). CONCLUSION: These findings demonstrated a potential compensatory mechanism involved in the link between the decline in gait speed and episodic memory, whereby baseline connectivity of the SMN and FPN may underlie subsequent maintenance of gait speed and cognitive function in old age.