Aging-Induced Increase in Top-Down Connectivity from DLPFC to SMA/M1 and Decrease in Inter-Limb Motor Coordination During Standing Tasks

This study aimed to investigate the effects of aging on inhibitory control from the prefrontal cortex (PFC) to the motor cortices and inter-limb coordination during dual task standing. Participants performed single-task and dual-task standing. Ground reaction force, center-of-pressure, muscle activity, and cortical activation were measured. The older group showed a greater effective connectivity index from the intra-hemispheric dorsolateral PFC (DLPFC) to supplementary motor area (SMA) (right, <italic>p</italic> = 0.009; left, <italic>p</italic> = 0.003) and left DLPFC to right M1 (<italic>p</italic> = 0.020)than the young group across task conditions. Also, the older group had greater inter-tibialis anterior coherence at 15–35 Hz (<italic>p</italic> = 0.001) and inter-soleus coherence at 35-55 Hz (<italic>p</italic> = 0.003) during dual-task than single-task standing. Furthermore, the older group showed greater variability of inter-foot coordination in the medial-lateral direction than the young group during dual-task standing (<italic>p</italic> = 0.031). Our results indicate that older adults present stronger top-down connectivity from DLPFC to SMA/M1 compared to young adults in both single-task and dual-task standing, highlighting an excitatory control deficit with aging. This failure to inhibit the DLPFC on SMA/M1 in older adults may lead to impaired motor coordination between lower limbs during dual-task standing.