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

Functional magnetic resonance imaging, or fMRI, is a popular neuroimaging method that enables us to obtain images of brain activity. In this video, I discuss how fMRI works, what is represented in a typical fMRI image, and some of the methodological problems associated with the use of fMRI.

TRANSCRIPT:

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.

References:

Poldrack RA, Baker CI, Durnez J, Gorgolewski KJ, Matthews PM, Munafò MR, Nichols TE, Poline JB, Vul E, Yarkoni T. Scanning the horizon: towards transparent and reproducible neuroimaging research. Nature Reviews Neuroscience. 2017 Feb;18(2):115-126. doi: 10.1038/nrn.2016.167.

Small SA, Heeger DJ. Functional Imaging of Cognition. In: Kandel ER, Schwartz JH, Jessell TM, eds. Principles of Neural Science, 5th ed. New York: McGraw-Hill; 2013.

Stamatakis EA, Orfanidou E, Papanicolaou AC. Functional Magnetic Resonance Imaging. In: Papanicolaou AC, ed. The Oxford Handbook of Functional Brain Imaging in Neuropsychology and Cognitive Neurosciences. New York: Oxford University Press; 2014.

[Scientist.Nick.A]

fMRI measures blood flow to specific brain areas, but blood concentrations don’t necessarily positively correlate with brain activity because brain activity is based on the presence of properly-shaped neurotransmitter molecules being released into synapses between brain cells and functional receptors being present and also, electricity (action potentials are electric signals that brain cells send down the long extension of a brain cell’s cell body called an axon). Just because blood is flowing to an area, does not mean all of that other stuff is happening and happening properly. Brain activity is in itself independent of blood flow, but sometimes blood flow to an area of the brain does positively correlate with brain activity, but not always because of what I just explained.

[howtomedicate]

Very useful video! You should also make one on CT-scans! Good job 👍

[tungoanuc]

Can you do a Video on "
fMRI image processing steps". I want to do it!

[ilovelemonisland]

Can you do a video on fMRI biomarkers?

[calcal]

I, a researcher in the field, estimate that 95% (possibly all in humans) of all published fMRI studies are worthless. The reason is that subject motion creates signal variance that swamps the BOLD signal. Although motion correction algorithms are applied to the data they simply do not work well enough to reduce the motion variance to an insignificant value. Most researchers know this to be true but carry on regardless because their career depends upon doing so. Other researchers are simply ignorant of the artifacts that make this method junk.

[stellaancimer]

Can it shows where is a problem? Like does it show Activity of amygdala? Ect..

[chloebl]

Hi, thanks for this video. I've got to write my masters' thesis for next Monday and got a question on event-related fMRI, can someone help me please ?

[markphilip]

when is fMRI favoured over other techniques?

[locustphysalis]

Isn’t that the MRI method with protons? I’m confused. What’s the difference in comparison to fMRI?

[georgen]

higher neural activity when the brain responds to more magnetic fields