People With Mild-to-Moderate Dementia Exhibit Increased Prefrontal Cortical Activity and Connectivity During Stepping Tasks Requiring Executive Control: A Cross-Sectional fNIRS Study

AIMS: To compare prefrontal cortical activation patterns and functional connectivity between older adults with mild-to-moderate dementia (MMD) and healthy older adults (HOA) during stepping tasks with different executive demands.
METHODS: This study recruited 26 HOA and 27 MMD who could walk independently for 10 meters. Participants were instructed to perform four trials of simple stepping (SS; repeated steps to the same target) and four trials of choice stepping (CS; steps to different targets), presented in randomized order, on a plastic stepping mat. Prefrontal cortical activity during the stepping tasks was measured using functional near-infrared spectroscopy (fNIRS). Cortical activation and functional connectivity between the HOA and MMD groups and between the SS and CS were compared.
RESULTS: The HOA group showed significantly increased cortical activity during CS compared to SS, with activation in the left dorsolateral prefrontal cortex (DLPFC) (p=0.029), right DLPFC (p=0.044) during tasks, and right frontopolar cortex (FPPFC) during starting phase (p=0.046). Compared with the HOA, MMD showed a significant increase in right DLPFC (p=0.009) and left DLPFC (p=0.034) during SS. The MMD exhibited heightened prefrontal functional connectivity in both SS and CS compared to the HOA, particularly in the connectivity between the right and left FPPFC (p = 0.042).
CONCLUSIONS: Older adults with mild-to-moderate dementia exhibit compensatory overactivation in the prefrontal cortex even during stepping tasks that require less executive control, along with impaired task-related modulation. These findings provide insights into a neurophysiological basis for reduced stepping adaptability in people with dementia.