The ERS power map in the theta band (4–8 Hz) during the oddball task showed that the patient group response was significantly increased in the left temporal pole at 250–500 ms (Fig. 3A), and was significantly increased in the dorsal and medial frontal and anterior portions of the anterior cingulate cortex in both hemispheres, and the left-hand portion of lateral temporal regions at 500–750 ms, compared to the control group (Fig. 3B). The theta band responds selectively to the encoding of new information related to the hippocampal theta induced in the cortex via hippocampo-cortical feedback loops [36, 51-55]. Significant theta ERS was found during the encoding phase for only those words that could be remembered later and only for correctly recognized targets during the actual recognition phase but not for distractors and unremembered targets [36]. An attentive state during complex task performance and meditative concentration is closely associated with high amplitude theta activity of the frontal midline and anterior cingulate cortex (ACC) [56].
