Temporal activities during P3 components on the working memory-related brain regions: N-back ERP study

In recent cognitive neuroscience, many studies have been conducted on the human working memory. However, the temporal activities in the working memory-related brain regions are not clear yet. To elucidate the temporal activities of the working memory-related brain regions, we studied the EEG P300 activities during n-back tasks with a source analysis. We elicited two P3 components in the P300 activities; the early P3 and late P3, respectively. Those appeared approximately at 300 ms and 360 ms in our n-back ERPs with the scalp EEG data. The amplitudes of the corresponding peaks showed changes in according with the working memory load. Then, we created a source model in our analysis to evaluate the temporal activities in the P3 components. This source model was defined by the sources seeded from fMRI meta-analysis of the n-back tasks, the additional sources in the orbitofrontal cortex and the visual cortex estimated with the late P3 and the P100 components. It has provided a valuable insight into the temporal brain activities at the positions of the sources. The early P3 was mainly induced by the dorsolateral prefrontal cortex, the ventrolateral prefrontal cortex, the inferior parietal lobule, the medial posterior parietal and the visual cortex. The late P3 was mainly induced by the medial premotor, the lateral premotor, the frontal pole and the orbitofrontal cortex. The contribution of the frontal pole and the orbitofrontal cortex had a peak approximately at 390 ms which appeared after the late P3 component. In this study, we have described our method to evaluate the temporal activities in the working memory-related brain regions during the n-back tasks. Our results elicited a contribution of a network in the brain regions including the prefrontal association area and the parietal association area in the P300 components of the n-back working memory task.