The default mode network and EEG alpha oscillations: An independent component analysis

The default mode network (DMN), typically studied with PET and fMRI, has inconsistent support in EEG research. This study tested whether blind decomposition methods could identify DMN-like spatial patterns in EEG data across traditional frequency bands, and whether those patterns relate to task demands. Data were collected during rest, an explicit facial affect judgment task, and a social game task. Only alpha band patterns overlapped substantially with the DMN and correlated with DMN-related functions. Spontaneous self-referential thoughts during rest were linked to enhanced alpha activity in the posterior DMN hub, while processing external stimuli disrupted this activity and caused partial alpha phase-locking. This suggests alpha oscillations primarily synchronize internal mental processes rather than processing external stimuli.

Study at a glance

Abstract

The default mode network (DMN) has been principally investigated using positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) and has received mixed support in electroencephalographic (EEG) studies. In particular, the existing evidence is too inconsistent to allow formulation of specific hypotheses linking DMN activity to traditional EEG frequency bands. In this study, we aimed to test whether blind decomposition methods are able to identify in EEG data spatial patterns resembling the DMN as it is described in PET and fMRI studies. Further we aimed to test a degree of task-relatedness of DMN patterns identified in the traditional EEG frequency bands. To answer these questions we collected data both in a resting state and during performance of two experimental tasks: an explicit judgment of facial affect and a social game task. Individual differences in amount of self-referential thoughts during the resting state were measured by a short self-report scale. Only alpha band spatial patterns simultaneously showed a considerable overlap with the DMN and high correlations with presumptive DMN function-related outcomes both in the resting state and during the social game task. Spontaneous self-referential thoughts were associated with enhanced alpha activity in the posterior DMN hub, whereas processing of DMN function-related external stimuli disrupted this activity and simultaneously caused partial alpha phase-locking to external events. This evidence implies that synchronization of internal mental processes, as opposed to the processing of external stimuli, might be the primary function of alpha oscillations which is bound to be related to activity of the DMN.