Resting-State EEG Aperiodic Exponent Moderates the Association Between Age and Memory Performance in Older Adults

Memory functions are susceptible to age-related cognitive decline, making it essential to explore the underlying neurophysiological mechanisms that contribute to memory function during healthy ageing. Resting-state EEG (rsEEG) parameters, particularly the aperiodic exponent, a marker of cortical excitation-inhibition balance, and individual alpha frequency (IAF), a correlate of neural processing efficiency, have demonstrated associations with ageing and cognitive functions. This study investigated associations between these rsEEG markers and performance across multiple memory systems in healthy older adults (n = 99) aged 50-84 years, specifically the moderating and mediating effects on memory and age-memory relationships across episodic, working, and visual short-term memory systems, assessed via computerised tasks. Results revealed significant moderating effects of the aperiodic exponent on age-related performance in episodic (EM) and visual short-term memory (VSTM). Notably, for individuals with a higher exponent, age was not significantly associated with EM or VSTM performance, whereas those with average and lower exponent values showed poorer performance with older age. These findings suggest that average and lower aperiodic exponents may reflect a marker of decrement in age-related memory performance and higher exponents may index an underlying protective mechanism against age-related memory decline. This investigation extends the current understanding of cognitive ageing mechanisms by identifying the aperiodic exponent as a potential biomarker explaining individual differences in cognitive ageing trajectories in older adult populations, particularly in EM and VSTM systems, and establishes a framework for studying neuroprotective mechanisms and developing interventions to preserve cognitive function in older adults.