title: Evidence that neurovascular coupling underlying the BOLD effect increases with age during childhood.
abstract: Functional MRI using blood-oxygen-level-dependent (BOLD) imaging has provided unprecedented insights into the maturation of the human brain. Task-based fMRI studies have shown BOLD signal increases with age during development (ages 5-18) for many cognitive domains such as language and executive function, while functional connectivity (resting-state) fMRI studies investigating regionally synchronous BOLD fluctuations have revealed a developing functional organization of the brain from a local into a more distributed architecture. However, interpretation of these results is confounded by the fact that the BOLD signal is directly related to blood oxygenation driven by changes in blood flow and only indirectly related to neuronal activity, and may thus be affected by changing neuronal-vascular coupling. BOLD signal and cerebral blood flow (CBF) were measured simultaneously in a cohort of 113 typically developing awake participants ages 3-18 performing a narrative comprehension task. Using a novel voxelwise wild bootstrap analysis technique, an increased ratio of BOLD signal to relative CBF signal change with age (indicative of increased neuronal-vascular coupling) was seen in the middle temporal gyri and the left inferior frontal gyrus. Additionally, evidence of decreased relative oxygen metabolism (indicative of decreased neuronal activity) with age was found in the same regions. These findings raise concern that results of developmental BOLD studies cannot be unambiguously attributed to neuronal activity. Astrocytes and astrocytic processes may significantly affect the maturing functional architecture of the brain, consistent with recent research demonstrating a key role for astrocytes in mediating increased CBF following neuronal activity and for astrocyte processes in modulating synaptic connectivity.
authors.affiliation: Pediatric Neuroimaging Research Consortium, Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.
authors.forename: Vincent J
authors.initials: VJ
authors.lastname: Schmithorst
authors.forename: Jennifer
authors.initials: J
authors.lastname: Vannest
authors.forename: Gregory
authors.initials: G
authors.lastname: Lee
authors.forename: Luis
authors.initials: L
authors.lastname: Hernandez-Garcia
authors.forename: Elena
authors.initials: E
authors.lastname: Plante
authors.forename: Akila
authors.initials: A
authors.lastname: Rajagopal
authors.forename: Scott K
authors.initials: SK
authors.lastname: Holland
mesh_terms: D000293:Adolescent; D000367:Age Factors; D001921:Brain / Q000098:blood supply* / Q000254:growth & development*; D001931:Brain Mapping; D002560:Cerebrovascular Circulation / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D010100:Oxygen / Q000097:blood
chemical_list: D010100:Oxygen
keywords: children; developmental studies; functional MRI; language processing; neuronal-vascular coupling