Nitrous oxide altered brain networks as people viewed flashing images

The gas weakened links between brain regions that help combine sensory and emotional information, and this was associated with greater unpleasantness.

Editorial illustration — not from the study.

Researchers used functional MRI to study healthy adults before and during administration of nitrous oxide at 35% in oxygen. While in the scanner, participants viewed a flashing checkerboard ring and rated its sensory qualities, including intensity and unpleasantness.

Nitrous oxide reduced the separation between large-scale brain networks and disrupted their usual hierarchy. The strongest changes occurred in higher-order networks involved in integrating information, while visual networks were relatively preserved. Weaker connections between the anterior insula, anterior cingulate and lateral occipital cortex were associated with greater reported unpleasantness.

Brain networks during nitrous oxide

Nitrous oxide reduced network modularity, meaning large brain networks became less distinct from one another, and disrupted their hierarchical organization. The largest effects were seen in higher-order integrative systems, while visual networks showed relative preservation. Nitrous oxide also reduced coupling between the anterior insula and the anterior cingulate and lateral occipital cortices. Greater decoupling among these regions was associated with greater subjective unpleasantness during the visual task.

Why the findings matter

The findings suggest that altered visual experiences under nitrous oxide may reflect changes in how the brain’s wider integrative and salience-related systems coordinate information, rather than major changes within visual networks themselves. The link between insula decoupling and unpleasantness also identifies a brain-network change associated with a specific subjective aspect of the experience.

Evidence and caveats

This was a task-based functional MRI study in healthy adults tested before and during a 35% nitrous oxide mixture in oxygen while viewing a flashing checkerboard pattern. The study found associations between connectivity changes and reported unpleasantness, but the abstract does not establish that the connectivity changes caused the experience. It also does not report the number of participants, and the findings come from a specific visual task and a healthy-adult sample, so their relevance to other doses, settings or populations is not established.

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