Medial prefrontal cortex generates frontal midline theta rhythm

FRONTAL midline theta rhythm (Fm theta) is a distinct theta activity of EEG in the frontal midline area that appears during concentrated performance o f mental tasks in normal subjects and reflects focused attentional processi ng. To tomographically visualize the source current density distributions o f Fm theta, we recorded Fm theta by using a 64-channel whole-bead MEG syste m from four healthy subjects, and applied a new analysis method, synthetic aperture magnetometry (SAM), an adaptive beam forming method. Fm theta was observed in the MEG signals over the bilateral frontal regions. SAM analysi s showed bilateral medial prefrontal cortices, including anterior cingulate cortex, as the source of Fm theta. This result suggests that focused atten tion is mainly related to medial prefrontal cortex. NeuroReport 10:675-679 (C) 1999 Lippincott Williams & Wilkins.