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Detecting activity-evoked pH changes in human brain
Journal article   Open access   Peer reviewed

Detecting activity-evoked pH changes in human brain

Vincent A Magnotta, Hye-Young Heo, Brian J Dlouhy, Nader S Dahdaleh, Robin L Follmer, Daniel R Thedens, Michael J Welsh and John A Wemmie
Proceedings of the National Academy of Sciences - PNAS, Vol.109(21), pp.8270-8273
05/22/2012
DOI: 10.1073/pnas.1205902109
PMCID: PMC3361452
PMID: 22566645
url
https://doi.org/10.1073/pnas.1205902109View
Published (Version of record) Open Access

Abstract

Localized pH changes have been suggested to occur in the brain during normal function. However, the existence of such pH changes has also been questioned. Lack of methods for noninvasively measuring pH with high spatial and temporal resolution has limited insight into this issue. Here we report that a magnetic resonance imaging (MRI) strategy, T 1 relaxation in the rotating frame (T 1 ρ), is sufficiently sensitive to detect widespread pH changes in the mouse and human brain evoked by systemically manipulating carbon dioxide or bicarbonate. Moreover, T 1 ρ detected a localized acidosis in the human visual cortex induced by a flashing checkerboard. Lactate measurements and pH-sensitive 31 P spectroscopy at the same site also identified a localized acidosis. Consistent with the established role for pH in blood flow recruitment, T 1 ρ correlated with blood oxygenation level-dependent contrast commonly used in functional MRI. However, T 1 ρ was not directly sensitive to blood oxygen content. These observations indicate that localized pH fluctuations occur in the human brain during normal function. Furthermore, they suggest a unique functional imaging strategy based on pH that is independent of traditional functional MRI contrast mechanisms.
 Biological Sciences Physical Sciences brain pH T1rho functional magnetic resonance imaging

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