Localizing the Sources of Modulations of the P3m Component by Task Difficulty

1The P3m is a late component of the event-related field (ERF) and is assumed to reflect the allocation of resources in various cognitive domains. The amplitude of the P3m can be affected by several task parameters, like stimulus probability, inter-stimulus interval and task difficulty. The task difficulty can alter the P3m amplitude, depending on which mechanisms are involved. The sources of the P3m are located in several brain areas, suggesting a widespread network generating the P3m. Which of these sources of the P3m give rise to the task-difficulty induced amplitude modulation are not well investigated. However, localizing these sources could pave the way for intervention studies with non-invasive brain stimulation methods, which might be suitable to modulate the pathologically altered P3m emerging in various psychiatric and neurodevelopmental disorders. We designed a MEG-study with a visual oddball-like task with two different task difficulties to 1) show decreased P3m amplitudes induced by increased task difficulty and 2) estimate the sources of this P3m modulation. Additionally, the influence of the increased task difficulty on behavioral outcomes were analyzed. The P3m amplitude decreased significantly in the hard condition compared to easy condition. Furthermore, the hit rate for standard trials decreased significantly, while the reaction times increased for both, targets and standards. For this specific visual oddball-like task, the sources of the task difficulty dependent P3m amplitude modulation are located in the centro-parietal regions.