Brain-Behavior Coupling During Cognitive-Postural Dual-Tasking in Older Adults With Mild Cognitive Impairment: An fNIRS Study

Mild cognitive impairment (MCI) is associated with subtle deficits in cognitive-motor integration and postural control; however, the cortical mechanisms underlying impaired cognitive-postural dual-task performance remain unclear. This study aimed to investigate behavioral alterations, cortical activation patterns, and brain-behavior coupling characteristics during cognitive-postural dual-tasking in older adults with MCI.

Fifty-three community-dwelling older adults were enrolled, including 26 individuals with MCI and 27 cognitively normal controls. Participants performed a verbal fluency task while maintaining upright standing under four dual-task conditions combining visual availability (eyes open/closed) and support-surface stability (stable/unstable). Postural performance was assessed using the anteroposterior stability index (API) and mediolateral stability index (MLI), while cognitive performance was evaluated using verbal fluency scores. Functional near-infrared spectroscopy (fNIRS) was used to measure task-related cortical activation in bilateral prefrontal, primary somatosensory, primary motor, and premotor cortices. Between-group comparisons, partial correlation analyses, and regression-based interaction analyses were conducted to examine alterations in brain-behavior relationships.

Compared with cognitively normal controls, participants with MCI exhibited poorer postural stability under dual-task conditions involving reduced visual input and/or unstable support surfaces. Reduced cortical activation was observed mainly in prefrontal regions during unstable support with eyes open and extended to sensorimotor-related regions under combined visual deprivation and unstable support. Brain-behavior associations differed between groups. In cognitively normal older adults, increased cortical activation was generally associated with better behavioral performance. In contrast, individuals with MCI showed stronger associations between reduced activation of distributed prefrontal-sensorimotor regions and impaired postural performance, particularly under the eyes-closed unstable-support condition. Regression-based interaction analysis further demonstrated a significant group-dependent association between right prefrontal activation and mediolateral postural stability.

Older adults with MCI exhibit altered brain-behavior coupling during cognitive-postural dual-task conditions involving sensory and postural constraints, characterized by altered relationships between prefrontal-sensorimotor cortical activation and behavioral performance. These findings provide new insights into the neural mechanisms underlying cognitive-motor dysfunction in MCI and highlight abnormal brain-behavior coupling as a potential feature of early functional impairment.