What
is fMRI?
fMRI
is a new technique based on the technology of magnetic resonance (MR) to
see the the physical structures of the brain without having to perform
surgical procedures. It works by measuring the oxygen consumption in different
areas of the brain, through a technique called BOLD (Blood Oxygen Level
Dependence). The differences between the magnetic properties of oxygenated
and deoxygenated hemoglobin are distinguished by the BOLD technique. Hence,
the measure of oxygen consumption is tied to processing or neural activation
and thereby maps the brain's functional activity.
More specifically, neurons in the brain require
oxygen to fire. Thus, once they do fire, there is a decrease in the oxygen
levels around the neuron. However, after the firing, there is a local dilation
of the capillaries to allow more oxygenated blood into the active area
of the brain. As a result there will be more oxygenated hemoglobin in the
area of the firing neuron which will be detected by the fMRI via the BOLD
technique.
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