The connection between ketamine and rumination may be visible in the brain’s rapidly shifting patterns of activity. A new randomized neuroimaging study suggests ketamine temporarily reduces a network state associated with repetitive negative thinking, offering a potential clue to how the drug produces fast psychological effects.
Published in Translational Psychiatry, the findings do not establish that disrupting this brain state treats depression. However, they identify a measurable neural process that could help researchers investigate why some effects of ketamine emerge so quickly.
Why Rumination Remains A Difficult Treatment Target
Rumination involves repeatedly returning to negative experiences, emotions, or concerns without reaching a productive resolution. It is strongly associated with depression but also appears across anxiety and other psychiatric conditions.
Researchers have increasingly viewed rumination as a problem of mental flexibility. Instead of smoothly shifting attention between internal reflection and goal-directed thinking, the brain may remain caught between competing modes of processing.
Previous imaging research has linked rumination to unusual coordination between the default mode network, which supports self-referential thought, and the frontoparietal network, which contributes to cognitive control. These systems often perform distinct functions, making their simultaneous recruitment particularly informative.
Tracking Ketamine And Rumination In Real Time
The investigators enrolled 75 healthy adults between ages 18 and 45 in a randomized, double-blind, placebo-controlled trial. After imaging exclusions, 62 participants remained in the principal analysis.
Participants received one of three treatment combinations: placebo followed by placebo, placebo followed by ketamine, or lamotrigine followed by ketamine. Lamotrigine was included because it inhibits presynaptic glutamate release and could potentially weaken effects associated with ketamine’s acute glutamatergic activity.
Resting-state functional MRI scans were collected before treatment, during the infusion, and 24 hours later. Researchers then used coactivation pattern analysis to identify recurring configurations of whole-brain activity rather than averaging connectivity across an entire scan.
A Dynamic View Of Network Activity
This study design matters because brain networks do not remain fixed. They repeatedly form, dissolve, and reorganize, sometimes within seconds.
The analysis identified seven recurring coactivation patterns. One was a hybrid state involving both the default mode and frontoparietal networks. At baseline, participants reporting greater trait rumination entered this state more frequently.
That association supports the theory that rumination involves difficulty separating internally focused processing from systems responsible for attention and cognitive control. The hybrid pattern may reflect a brain attempting to regulate self-focused thought without fully disengaging from it.
Ketamine Temporarily Reduced The Rumination-Linked State
During infusion, participants receiving ketamine spent substantially less time in the hybrid network state than those receiving placebo. Within the ketamine-only group, people with higher rumination scores showed larger reductions from baseline.
The change was temporary. By 24 hours after infusion, meaningful differences between the groups were no longer detectable.
Ketamine also reduced time spent in a canonical somatomotor network state during infusion. Because this network contributes to bodily sensation and movement-related processing, the exploratory finding may relate to ketamine’s effects on sensory experience, pain, or psychomotor function. The study did not directly test those possibilities.
Glutamate May Explain Only Part Of The Effect
Ketamine blocks NMDA receptors and is thought to produce a temporary increase in glutamatergic signaling that supports downstream synaptic plasticity. Lamotrigine offered the researchers a way to probe whether that glutamate surge contributed to the observed network changes.
Pretreatment with lamotrigine nominally reduced ketamine’s effects across the hybrid and somatomotor patterns. However, differences between the ketamine-only and lamotrigine-plus-ketamine groups did not reach conventional statistical significance.
The evidence therefore suggests possible partial glutamatergic involvement, not proof of a single mechanism. Ketamine’s effects on large-scale brain dynamics may involve multiple interacting neurochemical processes.
A Mechanistic Study With Important Boundaries
Unlike clinical studies examining symptom change after treatment, this trial captured network activity during active ketamine administration. Its whole-brain, time-sensitive method also allowed researchers to identify brief configurations that conventional connectivity averages may miss.
Still, the participants were healthy adults without psychiatric diagnoses. Rumination was measured through an optional follow-up questionnaire, and ketamine’s noticeable subjective effects may have weakened blinding. The relatively small final sample also makes replication essential.
The next step is to determine whether similar network changes occur in people with depression, whether they correspond to actual reductions in rumination, and whether they predict sustained clinical benefit. For now, the study provides a controlled snapshot of ketamine interrupting a brain state associated with repetitive negative thought.
Citations
Meiering MS, et al. “Ketamine’s Impact On Rumination-Related Brain Dynamics: Insights From A Randomized Controlled fMRI Trial.” Translational Psychiatry. 2026;16:417. https://doi.org/10.1038/s41398-026-04392-w
Vidal S, et al. “Effect Of Ketamine On Rumination In Treatment-Resistant Depressive Patients.” Journal of Clinical Psychopharmacology. 2020;40(6):607-610. https://doi.org/10.1097/JCP.0000000000001305
