This phenomenon is more closely correlated with the electrical activity of
neurons than with changes in blood flow, on which functional MRI is currently
based. In principle, this slower diffusion is reflected in dynamic changes in
the microscopic structure of the cerebral cortex, such as its cells swelling
when activated.
This “neuromechanical” coupling between cell shape and function thus offers a
radically different method for functional brain imaging that could represent
brain function more accurately than the neurovascular coupling on which
functional MRI is based today. This new method should also give scientists
greater insight into the cell processes underlying neuronal activation and how
water is involved in them. These results have just been published in PNAS.