DC-EEG recordings of mindfulness

•DC-EEG recordings revealed, in normal subjects, rhythmic waves lasting tens of minutes.•Some channels did not return to the baseline within one hour indicating the presence of even slower activity.•Archived EEG data that were obtained with DC amplifiers should be assessed for ultra-long wave durations.

ObjectiveTo assess the frequency spectrum of the normal waking human eyes-closed EEG while concentrating on a mental task.MethodsTen adult normal volunteers listened to a CD encouraging mindfulness for one hour and five minutes while their EEG was recorded on a 128 channel DC based ANT system. The software package BESA Research version 6.1 was used for data analysis. The data were subjected to topographic display, frequency as well as independent component analysis.ResultsNear-DC activity that extended beyond one hour, as well as rhythmic wave durations ranging from about 10 to 35 min, was observed in all subjects. For this task the major topographic distribution was mainly in frontal near midline areas and the inferior portions of the hemispheres.ConclusionsThe study demonstrated that rhythms below the infraslow band, as well as a near-DC component, exist in the normal human EEG. Their significance for health and disease now needs to be explored.SignificanceSince DC-based EEG/MEG systems are already in use by some laboratories, investigators are encouraged to include the exploration of these ultra-slow waves in the review of their data.