Neuroscience is a branch of biology dedicated to studying how the brain
works by focusing on the nervous system and neural networks of humans, in
particular, the neurons and their processes. Scientists have found out that
(1) some brain functions are mainly localized in specific regions of the
brain (“localization”); (2) a region necessary to a particular class of
behaviors/cognition does not mean that it is not involved in other brain
functions or that other brain regions do not contribute to the same class of
behaviors/cognition (“lack of bijection”); and (3) brains are somewhat
plastic or changeable on both small and large scale (“plasticity”).
Neuroscientists have developed and used many techniques to understand
brain functions. Functional Magnetic Resonance Imaging (fMRI) is one such
exciting technique of particular interest to educatiors. This functional
technique measures blood oxygenation levels, and records how blood flow
changes in the brain when the subject performs certain tasks or receives
certain stimuli. It should be pointed out that the fMRI technique does not
directly measure brain activity, but allows inference thereof.
The neuroscience basis for fMRI is the following. A brain activity consumes
energy but the brain cell (neuron) does not contain enough energy reserves
of oxygen or glucose. Therefore, when one brain region is involved in an
increased brain activity, fresh blood with more oxygenated hemoglobin will
be sent to that brain region quickly, a phenomenon called blood-oxygen-level
dependent (BOLD) response. For fMRI, a scanner detects changes in the
ratio of oxygenated hemoglobin and deoxygenated hemoglobin by measuring the
changes in the magnetic properties caused by the inflow of blood in the
brain during a BOLD response. Such a change of blood oxygenation level is
relatively small and the detection of the change requires a carefully
designed experiment with the help of a computer program to show the
statistically significant increase/decrease in signals before and after a
task or stimulus. The logic chain of fMRI is: blood flow increase detected
--> oxygen consumption increased -->neural activity
increased. The connections between steps of the logic chain are based on
inferences, not direct causation.