External task switches activate default mode regions without enhanced processing of the surrounding scene.
Ashley X Zhou1, John Duncan1, Daniel J Mitchell1
1MRC Cognition and Brain Sciences Unit, University of Cambridge, Cambridge, United Kingdom.
Imaging Neuroscience (Cambridge, Mass.)
|August 13, 2025
Summary
Default mode network (DMN) activity increases during external task switches, not just internal thought. This suggests DMN involvement in updating cognitive models during complex task shifts.
Area of Science:
- Neuroscience
- Cognitive Psychology
Background:
- The default mode network (DMN) typically deactivates during externally focused tasks.
- Previous studies reported increased DMN activity during demanding external task switches between cognitive domains.
Purpose of the Study:
- To replicate the DMN task-switch effect.
- To investigate if this effect relates to processing broader context, like background scenes.
- To test the hypothesis that DMN activity reflects cognitive model complexity.
Main Methods:
- Functional magnetic resonance imaging (fMRI) was used to measure brain activity.
- A task-switching paradigm was employed, involving switches between cognitive domains and within domains.
- Background scenes were presented and their processing was assessed.
Main Results:
- The core DMN showed significant activity during all task switches compared to repeats.
- Switches between rest and task elicited stronger DMN activity.
- Background scene processing did not differ based on switch type, despite attention and recall.
- DMN activity was similar for within-domain and between-domain switches.
Conclusions:
- External task switches activate the DMN independently of enhanced background scene processing.
- DMN modulation by task switches may reflect shifts in the current cognitive model.
- The complexity of the cognitive model appears to influence DMN activity during task switching.
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