SECOND by second changes in the brain’s pH can be visualised for the first time. This ability may provide fresh insights into learning, memory and disease.

Oxygen deprivation can alter the brain’s pH, and even normal brain signals from acidic neurotransmitters or metabolic by-products such as lactic acid may lead to local changes in pH. Studies in mice have also uncovered pH-sensitive receptors in brain areas involved in emotion and memory – although their function is something of a mystery.

“If these receptors are activated by pH change, it’s possible that abnormalities in this system could lead to changes in learning, memory and mood,” says Vincent Magnotta at the University of Iowa in Iowa City.

A common way of studying the brain is with an MRI scanner, which detects differences in the spin of protons in tissues according to water content. Although brain pH can be measured using a form of MRI called MR spectroscopy, it only detects changes that occur over minutes – not fast enough to keep up with the rapid pace of the brain.


T1ρ MRI analyses the interaction between spinning protons and other ions in a solution, which changes under different pHs. By tweaking the technique so that multiple measurements could be taken simultaneously, Magnotta and his colleagues have found that T1ρ MRI can detect changes in brain acidity happening over seconds.

Using the technique, they have shown that normal brain activity can trigger local changes in pH – something only speculated about until now (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1205902109).

Normal brain activity triggers changes in pH – something we could only speculate about until now

As well as providing insights into healthy brain function, pH imaging might also be used to detect early signs of degenerative diseases.