Fundamentally new MRI method developed to measure brain function in milliseconds

The speed of the human brain is remarkable: in a fraction of a second, neurons are activated, propagating thoughts and reactions to stimuli. But the speed with which we can follow non-invasively brain function with the help of an MRI is not as impressive. Functional MRI (fMRI), which measures the evolution of oxygen levels in the blood, has revolutionized the field of neuroscience by revealing functional aspects of the brain. But the changes fMRI is sensitive to can take up to six seconds in humans – a real eon in the brain's time. Investigators from Brigham and Women's Hospital, together with colleagues from King's College London and INSERM-Paris, have discovered a fundamentally new method of measuring brain function using a technology known as magnetic resonance elastography (MRE), an approach to create maps of tissue stiffness. using an MRI scanner. In an article published in Progress of science, the team presents data from preclinical studies indicating that the technique tracks the activity of brain function on a time scale of 100 milliseconds. Studies of the technique in human participants are underway.

"What fascinates me most is that it's an entirely new method, and new science has always intrigued it," said co-author Sam Patz, Ph.D. physicist at Brigham Department of Radiology and Professor of Radiology. at the Harvard Medical School. This work, which began as a presentiment and is now confirmed by rigorous experiments, represents the collaborative work of an international team dedicated to researching this new way of reproducing the functioning of the brain. "The data we publish has been obtained on mice, but the translation of this technology to humans is simple and the first studies are ongoing."

This work is the culmination of a five-year collaboration between Patz, the co-pen author, Ralph Sinkus Ph.D., and many others. Sinkus, physicist and professor at King & # 39; s College London and INSERM Paris, is a pioneer in the field of EDM and has played a key role in launching the research program on the ERM for preclinical trials in Patz's lab, Boston, as well as reported research. Patz and Sinkus refer to each other as an example of how a true collaborative relationship should work.

Although initially interested in applying MRE to the lungs, the team decided to also conduct brain tests. The results of these analyzes revealed something amazing: the acoustic cortex stiffened for no apparent reason. "These results were so unexpected that we had to pursue them, and it is this finding that triggered all the rest," Sinkus said. "It's a real interest in the science that made this possible."

Patz plugged one of the mouse's auditory ducts with a gel. Indeed, when he took another "elastogram" image of the mouse brain, he could see that the auditory cortex on the side of the brain that was treating the sound of that ear had started to soften. In repeated preclinical studies, this initial observation has been replicated, showing which regions of the brain stiffen or soften under different types of synchronization.

"The fascinating novelty of this approach is that the stiffening / softening of certain regions of the brain persists even when 100-millisecond stimuli are presented to the mouse," Patz said.

Sinkus and Patz both agreed that stiffness changes were related to neuronal activity, which allowed one to "see the brain thinking" almost in real time.

The team is now interested in using MRE to observe neuronal activity in the human brain, which could have consequences on the diagnosis and understanding of neurological pathologies in which the Neuronal activity may be slowed down, disrupted our reorientation, such as Alzheimer's disease, dementia, multiple sclerosis or epilepsy. .

The team's approach is based on new equipment to induce brain vibrations – an essential element for measuring brain rigidity via MRI. Patz compares the elastography device to maintaining an electric toothbrush against the head in order to create tiny mechanical waves that cross the brain. The standard ERM methodology has been used to measure waves as they pass through the brain, but a new mathematical approach of the Sinkus group has been implemented to create the elastograms from the raw data. The team also used a new MRE protocol to compare brain stiffness in two different functional states corresponding to a stimulus applied or not applied to the hind limb in mice. Researchers present data showing that stimulus modulation has influenced the location, phase, and intensity of changes in elasticity observed in the brain, which means that they can visualize regional responses in the brain when they occur at high speed.

"We think this will transform our ability to observe neuronal functional activity with implications for neurological pathologies," Patz said.