http://www.pnas.org/content/early/2013/06/25/1303178110.short
Abstract
Neuronal activity results in a
local increase in blood flow. This concept serves as the basis for
functional MRI. Still, this
approach remains indirect and may fail in
situations interfering with the neurovascular coupling mechanisms
(drugs, anesthesia).
Here we establish that water molecular
diffusion is directly modulated by underlying neuronal activity using a
rat forepaw
stimulation model under different
conditions of neuronal stimulation and neurovascular coupling. Under
nitroprusside infusion,
a neurovascular-coupling inhibitor, the
diffusion response and local field potentials were maintained, whereas
the hemodynamic
response was abolished. As diffusion MRI
reflects interactions of water molecules with obstacles (e.g., cell
membranes), the
observed changes point to a dynamic
modulation of the neural tissue structure upon activation, which remains
to be investigated.
These findings represent a significant
shift in concept from the current electrochemical and neurovascular
coupling principles
used for brain imaging, and open unique
avenues to investigate mechanisms underlying brain function.
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