CO2 poisoning can occur during medical conditions such as sleep apnea or emphysema, in adverse diving conditions, or from other geological causes. We know how CO2 creates physiological changes to blood flow and oxygen concentration, which can damage the brain. But less is known about how precisely CO2 disrupts brain activity.
A recent human study used two types of MRI (magnetic resonance imaging) to gauge CO2 levels and functional connectivity after breathing in CO2-enriched air. Additionally, the study used EEG (electroencephalogram) to determine electrical activity in the brain after CO2 inhalation.
The results found that there was a reduction in metabolic activity, a decrease in neural connectivity, and an increase in low arousal states after CO2 inhalation. These three findings correspond with each other to show how CO2 inhalation specifically causes an overall reduction of activity in the brain.
Xu F, Uh J, Brier MR, et al. The influence of carbon dioxide on brain activity and metabolism in conscious humans. Journal of Cerebral Blood Flow & Metabolism. (January 2011).