The influence of carbon dioxide on brain activity and metabolism in conscious humans

Feng Xu, Jinsoo Uh, Matthew R. Brier, John Hart, Uma S. Yezhuvath, Hong Gu, Yihong Yang, Hanzhang Lu

Research output: Contribution to journalArticlepeer-review

217 Scopus citations


A better understanding of carbon dioxide (CO2) effect on brain activity may have a profound impact on clinical studies using CO2 manipulation to assess cerebrovascular reserve and on the use of hypercapnia as a means to calibrate functional magnetic resonance imaging (fMRI) signal. This study investigates how an increase in blood CO2, via inhalation of 5% CO2, may alter brain activity in humans. Dynamic measurement of brain metabolism revealed that mild hypercapnia resulted in a suppression of cerebral metabolic rate of oxygen (CMRO 2) by 13.4%±2.3% (N14) and, furthermore, the CMRO2 change was proportional to the subject's end-tidal CO2 (Et-CO2) change. When using functional connectivity MRI (fcMRI) to assess the changes in resting-state neural activity, it was found that hypercapnia resulted in a reduction in all fcMRI indices assessed including cluster volume, cross-correlation coefficient, and amplitude of the fcMRI signal in the default-mode network (DMN). The extent of the reduction was more pronounced than similar indices obtained in visual-evoked fMRI, suggesting a selective suppression effect on resting-state neural activity. Scalp electroencephalogram (EEG) studies comparing hypercapnia with normocapnia conditions showed a relative increase in low frequency power in the EEG spectra, suggesting that the brain is entering a low arousal state on CO2 inhalation.

Original languageEnglish (US)
Pages (from-to)58-67
Number of pages10
JournalJournal of Cerebral Blood Flow and Metabolism
Issue number1
StatePublished - Jan 2011


  • carbon dioxide
  • cerebral metabolic rate of oxygen
  • electroencephalogram
  • functional connectivity MRI
  • hypercapnia

ASJC Scopus subject areas

  • Neurology
  • Clinical Neurology
  • Cardiology and Cardiovascular Medicine


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