The Effect of Postural Control on Attentional Resource Allocation in Alzheimer’s Disease: An Event-Related Potential Study

Objective To examine how the postural demand of quiet standing, compared to sitting, affects the allocation of attentional resources during a concurrent cognitive task in healthy older adults and individuals with Alzheimer’s disease (AD). Methods 87 healthy older adults (age 71.7 ± 4.2 years; MoCA 28.9 ± 1.1) and 16 individuals with AD (age 74.3 ± 5.1 years; MoCA 19.6 ± 6.3) completed a two-minute auditory novelty oddball task (50 stimuli: 80% frequent, 10% rare, 10% novelty) in both standing and sitting positions. Neural activity was recorded using electroencephalography (EEG). We used linear mixed models to compare P3 event-related potentials (ERPs) across groups and conditions, focusing on the P3b component (conscious stimulus evaluation) and the P3a component (automatic novelty detection). Behavioral outcomes were accuracy and reaction times on the oddball task, and sway velocity collected from a head-mounted accelerometer. Results A significant condition × group interaction was found for P3b latency in response to frequent stimuli ( p = 0.003). While sitting, the AD group showed shorter P3b latencies than healthy older adults ( p = 0.036). However, this pattern reversed under postural load: individuals with AD had significantly longer P3b latencies when standing compared to sitting ( p = 0.01), whereas healthy older adults showed the opposite pattern, with significantly decreased latencies ( p = 0.04). No significant effects were found for P3b amplitude or for the P3a component. Postural condition did not significantly impact behavioral outcomes in either group. Conclusions Quiet standing may impose a selective neural cost on individuals with AD, reflected in slower conscious cognitive processing, while appearing to act as an arousing factor that facilitates faster processing in healthy older adults. Maintaining posture might require a reallocation of limited attentional resources that disrupts higher-order processing in AD.