Exploring Cerebral Oxygenation and Executive Function in Older Adults with Subjective Cognitive Decline: A Dual Task Verbal Fluency and Walking Study

Abstract

Subjective cognitive decline (SCD) is increasingly recognized as a potential preclinical stage of Alzheimer's disease and related dementias; however, objective markers capable of detecting subtle neural changes during this stage remain limited. Functional near-infrared spectroscopy (fNIRS) offers a portable, non-invasive method for measuring cerebral oxygenation during dynamic cognitive-motor tasks and may provide a sensitive approach for investigating early functional changes associated with SCD. The present study examined cerebral oxygenation and executive functioning in older adults with and without SCD during single-task and cognitively demanding dual-task conditions. Twenty-eight community-dwelling older adults (14 with SCD and 14 without SCD) completed single cognitive, single motor, and dual-task walking conditions incorporating letter, semantic, and alternating verbal fluency while prefrontal cortex oxygenation was measured using fNIRS. Behavioural outcomes included gait speed and verbal fluency performance. Analyses revealed a significant task-by-SCD interaction for oxygenated hemoglobin (ΔHbO2); however, this interaction did not remain significant following Bonferroni adjusted post hoc comparisons. Significant task-by-hemisphere interactions were observed for both ΔHbO2 and deoxygenated hemoglobin (ΔHbR), with greater left prefrontal activation during dual-task performance. Behaviourally, gait speed and verbal fluency performance declined as task demands increased, demonstrating expected dual-task costs. Overall, the findings did not provide evidence of altered cerebral oxygenation or behavioural performance associated with SCD in this sample. However, the observed hemispheric activation patterns demonstrate that the dual-task paradigm successfully engaged prefrontal executive networks, highlighting the potential of combining fNIRS with ecologically valid cognitive-motor paradigms to further investigate early functional changes associated with subjective cognitive decline.