Two Different Populations within the Healthy Elderly: Lack of Conflict Detection in Those at Risk of Cognitive Decline

Sánchez-Moguel, Sergio M.; Alatorre-Cruz, Graciela C.; Juan Silva‐Pereyra; González-Salinas, Sofía; Sánchez-López, Javier; Otero, Gloria; Fernández, Thalı́a · 2018 · OpenAlex-citations

DOI: 10.3389/fnhum.2017.00658

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Summary

This study investigates whether healthy elderly adults with an electroencephalographic (EEG) risk of cognitive decline already exhibit specific cognitive impairments, particularly in inhibitory control. While excess theta activity in resting EEG is a known predictor of future cognitive decline, it remains unclear if this marker indicates current functional deficits beyond normal aging. The researchers aimed to determine if elderly individuals with theta excess show reduced inhibitory control compared to those with normal EEGs, using event-related potentials (ERPs) during a Counting-Stroop task to detect subclinical changes in neural processing. The study included 44 healthy older adults (aged >60) divided into two groups of 22 based on resting EEG characteristics: a Normal-EEG group with normal brain activity and a Theta-EEG group with abnormally high theta power (Z > 1.96). The groups were matched for age, intelligence quotient, education, and quality of life. Participants performed a Counting-Stroop task, where they counted the number of words presented on screen regardless of the word’s meaning, creating congruent and incongruent conditions. EEG data were recorded during the task, and ERPs were analyzed for specific components: N200, P300, and N500. The N500 component, a negative wave peaking between 500 and 700 ms, is specifically associated with the active inhibition of semantic interference. Behaviorally, the Normal-EEG group exhibited a significantly larger Stroop interference effect (longer reaction times for incongruent trials) than the Theta-EEG group, although both groups performed the task with similar accuracy. ERP analysis revealed distinct neural patterns between the groups. The Theta-EEG group showed a higher P300 amplitude compared to the Normal-EEG group. Crucially, the Theta-EEG group failed to exhibit the N500 effect, which was robust in the Normal-EEG group. This absence of the N500 component indicates a lack of active inhibitory processing to suppress semantic interference in the Theta-EEG group. The findings suggest that healthy elderly individuals with theta excess are not merely at risk for future decline but already possess a specific cognitive impairment characterized by a deficit in conflict detection and inhibitory control. The authors propose that the Theta-EEG group compensates for this lack of late-stage inhibition through different neural processes in earlier stages, allowing them to maintain behavioral performance similar to the Normal-EEG group. This study provides evidence that theta excess in resting EEG marks a distinct sub-population within the healthy elderly who have already begun to experience functional cognitive alterations, highlighting the utility of ERPs in detecting pre-clinical cognitive deficits.

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• cognitive aging