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2-Minute Neuroscience: Functional Magnetic Resonance Imaging (fMRI)

Functional magnetic resonance imaging, or fMRI, is a type of neuroimaging used to obtain

images of brain activity.

fMRI involves exposing the brain to multiple magnetic fields, and relies

on the observation that protons in the nuclei of hydrogen atoms respond to this procedure

by emitting an electromagnetic signal that can be detected by the fMRI scanner.

The fMRI scanner is capable of determining some of the properties of the tissue the signal

came from, and can use this information to reconstruct a high-resolution image of the

brain.

Additionally, the fMRI scanner can detect differences in the magnetic properties of

oxygenated vs. deoxygenated blood, and thus can identify changes in levels of oxygenated

blood in different regions of the brain using a method called blood-oxygen-level-dependent,

or BOLD, contrast.

BOLD is typically what enables us to identify which brain areas are most active in fMRI.

Areas of the brain that are more active tend to receive higher levels of oxygenated blood.

Thus, higher levels of oxygenated blood in a particular brain region are believed to

correspond to higher neural activity in that region.

On a typical fMRI image, color-coding is used to represent differences in the level of oxygenated

blood and thus differences in activity.

Activity in those areas can then be associated with whatever task was performed at the time

of the scan.

fMRI was developed in the early 1990s and since has become a very popular neuroimaging

method.

Nevertheless, in its short history fMRI research has been plagued by issues like small sample

sizes, the use of methods that lead to a high number of false positives, and a small proportion

of study results that have been independently reproduced.

As the field has become more aware of these problems, many researchers have begun to adjust

their approach to address them.