The Impact of Cognitive Reserve on Lateralization of EEG Phase-Locking Responses During Working Memory Tasks

Cognitive reserve (CR), shaped by the interaction of lifestyle and genetics, enhances the efficient use of neural resources, allowing individuals with higher reserve to require less neural activity to accomplish a task than those with lower reserve. Although not solely a mechanism for neural efficiency, hemispheric asymmetries contribute to it through the lateralization of cognitive processes across hemispheres. It is hypothesized that CR may influence the degree of asymmetry in neural activity during various cognitive processes. The aims of this study were to explore the effects of CR on verbal and visuospatial working memory performance and its relationship with the degree of asymmetry in 2-9 Hz phase-locking responses. The data were collected in two separate laboratories: one in Turkey and one in Germany. The sample included 33 Turkish and 18 German participants, all of whom completed verbal and visuospatial Sternberg tasks at two difficulty levels (one-item and three-item). The behavioral performance parameter was d' value, with EEG asymmetry calculated via the laterality coefficient (LC) formula. Under conditions of increased task difficulty, the LCs in the verbal task and CR scores had significant associations, especially in the parietal electrode pairs. Similarly, the LCs in the visuospatial task had significant associations with CR scores in the parietal and occipital electrode pairs. Furthermore, phase-locking responses were significantly higher in the right hemisphere across both tasks. These findings suggest that CR influences neural asymmetry, emphasizing the right hemisphere's role in CR and its potential as a therapeutic target.