Differential Processing of Hierarchical Visual Stimuli in Young and Older Healthy Adults: An Event-Related Potentials (ERP) Study

摘要

Objective: In tasks involving hierarchical stimuli, young subjects typically show faster RTs and higher accuracy rates in discriminating target stimuli at the global level than at the local level. This pattern of performance is called the global precedence effect (GPE). As individuals age, this patterns shifts to a local precedence effect (LPE). The purpose of this study was to determine whether the decline in GPE in older adults may be due to impairment of grouping processes. Method: The authors recorded event-related potentials (ERP) while young and elderly subjects performed a global/local task in response to hierarchical stimuli, and they focused on the P300 component as an index of grouping processes. Results: Compared to young subjects, elderly individuals showed a lower rate of correct discrimination in global processing conditions, but a higher rate of correct responses in local processing conditions, confirming a shift from a GPE to a LPE during aging. Interestingly, the P300 amplitude increased selectively during global processing in young adults but was not modulated by processing level in older participants. By contrast, the modulation of the early component N2 as a function of precedence level remained preserved in older subjects. Conclusion: The results suggest that the precedence level may depend on early processes that are unaffected during aging. This may explain the preservation of local precedence effect in elderly individuals. However, global processing may depend on extra attentional processing occurring at later stages. The alteration of later processing may explain the decline in global precedence during aging.