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

Summary

Functional magnetic resonance imaging (fMRI) is a neuroimaging technique used to estimate brain activity. It exposes the brain to magnetic fields and detects signals from hydrogen protons. The scanner uses these signals to reconstruct images of the brain.

A typical fMRI image highlights activity through blood-oxygen-level-dependent (BOLD) contrast. Oxygenated and deoxygenated blood have different magnetic properties, allowing the scanner to detect changes in oxygenated blood across brain regions. More active regions tend to receive more oxygenated blood, so these changes serve as an indirect indicator of neural activity. Images often use color to display differences in the signal, which researchers can compare with the task performed during the scan.

How fMRI is used

1. Apply magnetic fields and detect signals from hydrogen protons in the brain.
2. Use the signals to reconstruct an image of brain tissue.
3. Measure differences associated with oxygenated and deoxygenated blood.
4. Use BOLD contrast to identify changes in oxygenated blood as an indicator of relative brain activity.
5. Compare activity patterns with the task performed during the scan.

Limitations and research concerns

• Some fMRI studies have used small sample sizes.
• Certain methods have produced high numbers of false positives.
• A relatively small proportion of study findings have been independently reproduced.
• Researchers have increasingly adjusted their methods in response to these concerns.

Speaker/source

A single narrator explains fMRI.