Effects of predicted Khamisiyah exposure on default mode network resting state functional connectivity in Gulf War Veterans.
Linda L Chao, Salvatore Torrisi
Frontiers in toxicology 2026 DOI: 10.3389/ftox.2026.1772515 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Cross-sectional observational neuroimaging study Peer reviewed |
|---|---|
| Sample size | 41 |
| Population | Gulf War veterans (19 with and 22 without predicted exposure to the Khamisiyah organophosphorus nerve agent plume) |
| Measures | Conners Continuous Performance Test (CPT) |
| Topics | Default mode network |
| Keywords | Gulf war Attention Nerve agents Neuroimaging Resting-State FMRI |
| Key findings | Gulf War veterans with predicted exposure to the Khamisiyah nerve agent plume showed weaker default mode network connectivity between the left posterior cingulate cortex and the caudal right anterior cingulate cortex, and smaller left hippocampal volume, compared with unexposed veterans. The authors state that the cross-sectional design precludes causal conclusions and that the connectivity finding warrants replication in a larger independent sample. |
Abstract
Potentially more than 100,000 US troops were exposed to organophosphorus (OP) nerve agents when an ammunition bunker at Khamisiyah, Iraq was destroyed shortly after the end of the 1991 Gulf War (GW). We previously reported evidence of differences in brain structure and function in GW veterans with predicted exposure to the Khamisiyah plume compared to veterans without predicted exposure. Here, we investigate the effects of predicted exposure to the Khamisiyah plume on brain functional connectivity in the default mode network (DMN). Forty-one GW veterans (19 with and 22 without predicted exposure) underwent structural and resting-state magnetic resonance imaging (MRI) on a 3 Tesla scanner. Differences in DMN connectivity between veterans with and without predicted Khamisiyah exposure were examined using a left posterior cingulate cortex (PCC) seed-based analysis in AFNI. FreeSurfer was used to derive quantitative estimates of total hippocampal volume. The veterans were also assessed with the Conners Continuous Performance Test (CPT). Compared to veterans without predicted exposure, those with predicted Khamisiyah exposure demonstrated weaker connectivity between the left PCC and a cluster in the caudal right anterior cingulate cortex (ACC). Veterans with predicted exposure also had smaller left hippocampal volume compared to unexposed veterans. Although the cross-sectional nature of this study precludes conclusions about causality, the finding of decreased DMN functional connectivity in GW veterans with predicted Khamisiyah exposure warrants replication in a larger, independent sample. If confirmed, this result would add to the literature suggesting persistent differences in brain function between deployed GW veterans with and without predicted Khamisiyah exposure and argue for further investigation into the long-term effects of GW-deployment related exposures.
Comparable studies
Other experimental studies on default mode network, most cited first.
| Study | Year | Design | Participants |
|---|---|---|---|
| Functional connectivity of default mode network components: Correlation, anticorrelation, and causality Healthy subjects | 2008 | Observational study using resting-state fMRI and seed correlation analysis | |
| Patterns of Brain Activity Supporting Autobiographical Memory, Prospection, and Theory of Mind, and Their Relationship to the Default Mode Network Healthy subjects | 2009 | Experimental study using fMRI | |
| Dynamic reconfiguration of the default mode network during narrative comprehension Human subjects | 2016 | Experimental study | |
| Broadband Cortical Desynchronization Underlies the Human Psychedelic State Healthy human participants | 2013 | Experimental study | |
| The brain on art: intense aesthetic experience activates the default mode network Human observers | 2012 | Observational study with fMRI and behavioral analysis |