Behavioral variability and preparatory ERPs as neurobehavioral markers of mild cognitive impairment risk in older adults

Mild cognitive impairment (MCI) represents a transitional stage between normal aging and dementia, yet sensitive behavioral and neural markers of early cognitive decline remain to be fully characterized. Increasing evidence suggests that instability of proactive control mechanisms, rather than generalized slowing, may play a critical role in early cognitive impairment. The present study investigated whether behavioral variability and preparatory neural activity constitute neurobehavioral markers of global cognitive functioning in older adults. Ninety‑two older adults (65–89 years) completed a discriminative response task while electroencephalography was recorded. Behavioral performance was quantified using mean response time, error rate, and the intra‑individual coefficient of variation of response time (ICV). Preparatory neural activity was indexed by the Bereitschaftspotential (BP) and prefrontal negativity (pN) measured in the pre‑stimulus interval. Global cognition was assessed using the Montreal Cognitive Assessment (MoCA), analyzed both categorically (MCI‑range vs. cognitively normal) and continuously. Group comparisons, correlational analyses, regression models, and mediation analyses were conducted. Compared with cognitively normal participants, individuals in the MCI range exhibited significantly greater behavioral variability (higher ICV) and reduced preparatory neural activity (attenuated BP and pN amplitudes), while mean response time did not differ between groups. Across the entire sample, higher ICV was associated with lower MoCA scores, whereas larger BP and pN amplitudes were associated with better global cognition. Behavioral instability and preparatory neural activity independently predicted MoCA scores in continuous models. Mediation analyses indicated that ICV and preparatory ERP measures partially mediated the relationship between age and cognitive performance. The present findings demonstrate that behavioral instability and reduced preparatory neural engagement are closely linked to global cognitive performance and MCI-range in older adults. By integrating behavioral and pre‑stimulus electrophysiological measures, this study supports a neurobehavioral framework in which proactive control instability is associated with early cognitive decline. Preparatory processes emerge as sensitive and informative markers linked with variability in cognitive functioning in aging, with potential relevance for understanding early neurobehavioral changes.