P3 topographical change with task familiarization and task complexity.

The P3 event-related potential (ERP) component is usually reported as having a centro-parietal maximum. However, a more frontal P3 topography is also evident in early-session trials which may be masked by averaging over the entire session, and is also present longer in elderly subjects. This maintenance of hyperfrontal topography is interpreted as a sign of reduced prefrontal adaptive functioning. In the present study, P3 amplitude was examined in young adults to determine: (1) how early in the test session the reduction in hyperfrontality occurs; and (2) the effect of task complexity on the P3 amplitude across electrode sites (Fz, Cz, Pz). ERPs were elicited using a working memory n-back task. Single-trial ERP waveforms were averaged in successive blocks of five trials. There was a greater decrease in P3 amplitude at Fz compared to Cz and Pz sites after the first block, and the decrease reached an asymptote by the third block. The results are interpreted as indicating rapid decrease in initial P3 hyperfrontality for a simple task in young adults, and an increased ratio of P3 amplitude at frontal versus posterior sites in more complex tasks.