Task complexity and habituation effects on frontal P300 topography

The P3(00) event-related potential (ERP) component is usually reported as having a centroparietal maximum. However, the P3 topography is more frontal in early-session trials which may be masked by averaging over the entire session and is evident longer into the test session among elderly subjects. This hyperfrontality is interpreted as a sign of poor prefrontal adaptive functioning. In the present study, P3 amplitude was examined in university students to determine how early a change in amplitude would be evident and the effect of task complexity on the amplitude across electrode sites. ERPs were elicited using a working-memory n-back task where participants pressed a key to target letter presentations in three conditions of increasing complexity. Single-trial ERP waveforms were then averaged in successive sequences of five trials. Results revealed a greater decrease in frontal P3 amplitude compared to the central and parietal P3 after the first block of five target trials until the third block. The results are interpreted as indicating rapid decrease in hyperfrontality with habituation to an easy task. Increases in task complexity (the 2-back paradigm), however, reduced this frontal P3 attenuation. Results support a P3 ERP model of hyperfrontality reflecting short-term adaptive function by the prefrontal cortex.