Task complexity and habituation effects on frontal P300 topography

The P3(00) event-related potential (ERP) component is usually reported as h aving a centro-parietal maximum. However, the P3 topography is more frontal in early-session trials which may be masked by averaging over the entire s ession and is evident longer into the test session among elderly subjects. This hyperfrontality is interpreted as a sign of poor prefrontal adaptive f unctioning. Tn the present study, P3 amplitude was examined in university s tudents to deter mine 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 presse d a key to target letter presentations in three conditions of increasing co mplexity. Single-trial ERP waveforms were then averaged in successive seque nces of five trials. Results revealed a greater decrease in frontal P3 ampl itude compared to the central and parietal P3 after the first block of five target trials until the third block. The results are interpreted as indica ting rapid decrease in hyperfrontality with habituation to an easy task. In creases in task complexity (the 2-back paradigm), however, reduced this fro ntal P3 attenuation. Results support a P3 ERP model of hyperfrontality refl ecting short-term adaptive function by the pre-frontal cortex. (C) 2001 Aca demic Press.