Default-mode network activity is retained in the isolated hemisphere of people after hemispherotomy.
Tobias Bauer, Charlotte Gauvry, Sebastian Markett, Thomas Kreter-Schönleber, Valeri Borger, Hartmut Vatter, Josemir W. Sander, Markus Gabriel, Alexander Radbruch, Rainer Surges, Theodor Rüber
Brain Communications 2026 DOI: 10.1093/braincomms/fcag211 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Prospective case-control study Peer reviewed |
|---|---|
| Sample size | 50 |
| Population | Individuals post-hemispherotomy and healthy controls |
| Intervention | Hemispherotomy |
| Topics | Default mode network |
| Keywords | Consciousness Epilepsy surgery Functional MRI |
| Key findings | Default-mode network activity persists in isolated hemispheres, meeting a necessary condition for consciousness, but does not alone confirm conscious awareness. |
Abstract
Hemispherotomy is a surgical intervention for severe drug-resistant epilepsy that fully disconnects the lesional brain hemisphere from the rest of the nervous system. This creates a rare opportunity to explore whether consciousness can be sustained without external input. The default-mode network, linked to introspective mental activity, is considered a necessary, though not sufficient, condition for consciousness. In this prospective case-control study, resting-state functional MRI data from 26 individuals post-hemispherotomy and 24 healthy controls were analysed. Default-mode network activity was assessed using seed-to-voxel correlations based on the peak activity in the precuneus of controls, delineated by group independent component analysis. In connected hemispheres, typical default-mode network patterns were preserved and did not differ significantly from controls. Isolated hemispheres also showed preserved positive default-mode network connectivity, though negative connectivity was significantly reduced compared to controls. In two patients with both pre- and post-surgical scans, the individual default-mode network remained detectable but was divided between the isolated and connected hemispheres. These findings suggest that default-mode network activity persists in isolated hemispheres, meeting a necessary condition for consciousness. However, the presence of default-mode network activity alone does not confirm conscious awareness, encouraging further investigation into the neural correlates of consciousness in isolated hemispheres.
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
Cites 8
- A default mode of brain function Proceedings of the National Academy of Sciences January 16, 2001
- A Theoretically Based Index of Consciousness Independent of Sensory Processing and Behavior Science Translational Medicine August 14, 2013
- Breakdown of within- and between-network Resting State Functional Magnetic Resonance Imaging Connectivity during Propofol-induced Loss of Consciousness Anesthesiology September 30, 2010
- The Default Mode Network in Healthy Individuals: A Systematic Review and Meta-Analysis Brain Connectivity December 5, 2016
- Resting-state Network-specific Breakdown of Functional Connectivity during Ketamine Alteration of Consciousness in Volunteers Anesthesiology August 9, 2016
and 3 more in the library