The brain's functional activity and connectivity can be significantly affected by acute carbon monoxide (CO) poisoning, potentially leading to delayed neurological sequelae (DNS). To better understand the impact of CO poisoning on the brain, a study was conducted involving 74 subjects, including 18 DNS patients, 26 non-DNS patients, and 30 healthy controls. The study used various analysis methods, such as amplitude of low-frequency fluctuation and Granger causality analysis, to assess functional activity and connectivity in the brain. The results showed that DNS patients exhibited altered functional activity in specific nodes of the visual network, sensorimotor network, and executive control network. These changes in functional activity were detected using Gaussian random field correction, which allows for the identification of significant differences in brain activity between groups. The study also found significant changes in functional connectivity (FC) between different networks in the brain. Altered FC values were detected in the nodes of the visual network, default mode network, executive control network, sensorimotor network, and the cerebello-cortical motor loop nodes. Notably, the visual network exhibited hyperactivity, which had an inhibitory effect on the default mode network and sensorimotor network. In contrast, the default mode network showed hypoactivity and received excitatory influences from the anterior cerebellar and executive control network nodes. The changes in connectivity between these networks were associated with the clinical severity of CO poisoning, suggesting that the severity of poisoning may be related to the extent of changes in brain functional activity and connectivity. Overall, the study's findings highlight the significant changes in neural functional activity and connectivity that occur in DNS patients, which may contribute to the development of delayed neurological sequelae and are associated with the severity of CO poisoning. These results have important implications for our understanding of the effects of CO poisoning on the brain and may inform the development of novel therapeutic approaches for preventing or treating DNS. Link: https://pubmed.ncbi.nlm.nih.gov/40345557/