Epileptic discharges affect the default mode network--FMRI and intracerebral EEG evidence.
Firas Fahoum, Rina Zelmann, Louise Tyvaert, François Dubeau, Jean Gotman
PLoS One 2013 DOI: 10.1371/journal.pone.0068038 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Observational study Peer reviewed |
|---|---|
| Sample size | 6 |
| Population | Epilepsy patients undergoing scalp EEG-fMRI and stereotaxic intracerebral EEG (SEEG) |
| Topics | Default mode network |
| Key findings | During interictal epileptic discharges, DMN regions showed both decreased metabolic demand on fMRI and an EEG pattern of reduced gamma (50-150 Hz) and increased lower-frequency (<30 Hz) power, changes absent in non-DMN regions. The authors argue these findings confirm a direct relationship between DMN BOLD activity and EEG activity and suggest epileptic activity may momentarily reduce consciousness level and cognitive reserve. |
Abstract
Functional neuroimaging studies of epilepsy patients often show, at the time of epileptic activity, deactivation in default mode network (DMN) regions, which is hypothesized to reflect altered consciousness. We aimed to study the metabolic and electrophysiological correlates of these changes in the DMN regions. We studied six epilepsy patients that underwent scalp EEG-fMRI and later stereotaxic intracerebral EEG (SEEG) sampling regions of DMN (posterior cingulate cortex, Pre-cuneus, inferior parietal lobule, medial prefrontal cortex and dorsolateral frontal cortex) as well as non-DMN regions. SEEG recordings were subject to frequency analyses comparing sections with interictal epileptic discharges (IED) to IED-free baselines in the IED-generating region, DMN and non-DMN regions. EEG-fMRI and SEEG were obtained at rest. During IEDs, EEG-fMRI demonstrated deactivation in various DMN nodes in 5 of 6 patients, most frequently the pre-cuneus and inferior parietal lobule, and less frequently the other DMN nodes. SEEG analyses demonstrated decrease in gamma power (50-150 Hz), and increase in the power of lower frequencies (<30 Hz) at times of IEDs, in at least one DMN node in all patients. These changes were not apparent in the non-DMN regions. We demonstrate that, at the time of IEDs, DMN regions decrease their metabolic demand and undergo an EEG change consisting of decreased gamma and increased lower frequencies. These findings, specific to DMN regions, confirm in a pathological condition a direct relationship between DMN BOLD activity and EEG activity. They indicate that epileptic activity affects the DMN, and therefore may momentarily reduce the consciousness level and cognitive reserve.
Comparable studies
Other observational and cohort studies on default mode network, most cited first.
| Study | Year | Design | Participants |
|---|---|---|---|
| A default mode of brain function Normal adult human brain | 2001 | Observational study | |
| Resting-State Functional Connectivity Reflects Structural Connectivity in the Default Mode Network Healthy subjects | 2008 | Observational cohort | |
| Meditation experience is associated with increased cortical thickness Participants with extensive Insight meditation experience and matched controls | 2005 | Observational cohort | n = 20 |
| Meditation experience is associated with differences in default mode network activity and connectivity Experienced meditators and matched meditation-naive controls | 2011 | Observational cohort | |
| The precuneus/posterior cingulate cortex plays a pivotal role in the default mode network: Evidence from a partial correlation network analysis Healthy subjects | 2008 | Observational study |
Citations in the library
Cited by 2
Cites 3
- A default mode of brain function Proceedings of the National Academy of Sciences January 16, 2001
- Development of functional and structural connectivity within the default mode network in young children Neuroimage April 11, 2010
- Why do seizures cause loss of consciousness? The Neuroscientist October 2003