Exploring the mechanism of the age-related P3 anterior shift

The aim of this study was to explore the mechanism of the age-related P3 anterior shift using high-precision temporal principal components analysis (tPCA). Continuous EEG was recorded from younger and older adults while completing a two-stimulus visual oddball task. tPCA input was narrowed to the P3 range to enhance precision and reveal potentially overlapping temporal components. eLORETA modelled group and condition-related differences in component sources to further understanding of the neurobiology of the P3 anterior shift. Target P3a, P3b and nontarget P3/l-P3 (late P3) evidenced the expected anterior shift. P3 component amplitudes were reduced for older compared to younger adults across both stimulus types, consistent with the P3 'ageing effect'. All P3 components showed age-related differences in activation in multiple and diffuse sources, indicating neural processing beyond frontal regions (i.e., neural broadening). Findings suggest a dedifferentiation rather than compensation mechanism, as reduced P3 target amplitudes reflect attenuated responding to a preferred stimulus, and the anterior shift to nontargets indicates decreased processing selectivity to a non-preferred stimulus.