Title:  Aging Effect on Effective Connectivity within the Prefrontal-Motor Network and Postural-Related Muscle Responses during Dual-Task Paradigms

Program: Biomedical Engineering PhD

Committee Chair: Shuqi Zhang

Committee: Shuqi Zhang, Clare Fitzpatrick, Benjamin Johnson, Junhong Zhou

Abstract: Falls are highly prevalent among older adults, often resulting from impaired postural automaticity. This work investigates the neuromechanisms underlying this impairment by examining inhibitory control within the prefrontal-motor network and its impact on postural-related muscle responses in response to the secondary cognitive task. Three studies were conducted. First, dual-task standing experiments revealed that older adults exhibited overactivation of the prefrontal-motor cortex, leading to inappropriate ankle muscle responses. This was accompanied by stronger top-down connectivity from the dorsolateral prefrontal cortex (DLPFC) to the supplementary motor area (SMA) and primary motor cortex (M1), suggesting age-related deficits in inhibitory control. Second, when maintaining a voluntary forward-leaning posture with visual feedback, older adults showed increased reliance on excitatory influence from the DLPFC to the SMA/premotor cortex, but without improvement in reciprocal ankle control—indicating neural dedifferentiation. Third, analysis of center of pressure (CoP) signals during dual-task standing showed that older adults had enhanced low-frequency (0–0.5 Hz) oscillations, reflecting reduced postural automaticity and increased dependence on sensory feedback. Together, these findings reveal a more specific neural mechanism underlying increased fall risk in aging. Moreover, low-frequency CoP oscillations may serve as a non-invasive biomechanical biomarker for early detection and intervention evaluation.