title: The influence of mild carbon dioxide on brain functional homotopy using resting-state fMRI.
abstract: Homotopy reflects the intrinsic functional architecture of the brain through synchronized spontaneous activity between corresponding bilateral regions, measured as voxel mirrored homotopic connectivity (VMHC). Hypercapnia is known to have clear impact on brain hemodynamics through vasodilation, but have unclear effect on neuronal activity. This study investigates the effect of hypercapnia on brain homotopy, achieved by breathing 5% carbon dioxide (CO2 ) gas mixture. A total of 14 healthy volunteers completed three resting state functional MRI (RS-fMRI) scans, the first and third under normocapnia and the second under hypercapnia. VMHC measures were calculated as the correlation between the BOLD signal of each voxel and its counterpart in the opposite hemisphere. Group analysis was performed between the hypercapnic and normocapnic VMHC maps. VMHC showed a diffused decrease in response to hypercapnia. Significant regional decreases in VMHC were observed in all anatomical lobes, except for the occipital lobe, in the following functional hierarchical subdivisions: the primary sensory-motor, unimodal, heteromodal, paralimbic, as well as in the following functional networks: ventral attention, somatomotor, default frontoparietal, and dorsal attention. Our observation that brain homotopy in RS-fMRI is affected by arterial CO2 levels suggests that caution should be used when comparing RS-fMRI data between healthy controls and patients with pulmonary diseases and unusual respiratory patterns such as sleep apnea or chronic obstructive pulmonary disease.
authors.affiliation: Radiology/Center for Biomedical Imaging, New York University School of Medicine, New York, New York.
authors.forename: Olga
authors.initials: O
authors.lastname: Marshall
authors.affiliation: Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas.
authors.forename: Jinsoo
authors.initials: J
authors.lastname: Uh
authors.affiliation: Center for the Developing Brain, Child Mind Institute, New York, New York.
authors.forename: Daniel
authors.initials: D
authors.lastname: Lurie
authors.affiliation: Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas.|Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors.forename: Hanzhang
authors.initials: H
authors.lastname: Lu
authors.affiliation: Center for the Developing Brain, Child Mind Institute, New York, New York.|Nathan S Kline Institute for Psychiatric Research, New York.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Milham
authors.affiliation: Radiology/Center for Biomedical Imaging, New York University School of Medicine, New York, New York.
authors.forename: Yulin
authors.initials: Y
authors.lastname: Ge
mesh_terms: D000328:Adult; D001921:Brain / Q000187:drug effects*; D001931:Brain Mapping; D002245:Carbon Dioxide / Q000097:blood / Q000494:pharmacology*; D002540:Cerebral Cortex / Q000187:drug effects / Q000503:physiopathology; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology*; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D009415:Nerve Net / Q000187:drug effects / Q000503:physiopathology; D010100:Oxygen / Q000097:blood; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology; D055815:Young Adult
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen
keywords: brain; connectivity; functional MRI; homotopy; hypercapnia; resting-state