fMRI: Functional Magnetic Resonance Imaging

Functional MRI (fMRI) is a magnetic resonance imaging (MRI)-based neuroimaging technique which allows us to detect the brain areas which are involved in a task, a process or an emotion.

Functional MRI sequence

Echo planar imaging (EPI), a fast magnetic resonance imaging (MRI) technique, is used to sequentially acquire brain images every few seconds (TR = 2000 ms - 4000 ms) during several minutes. These images are of medium quality and prone to susceptibility artifacts, but their short acquisition time makes them ideal for fMRI acquisitions. MRI is a safe examination provided MRI safety rules are respected.

fMRI Paradigm

fMRI cannot detect absolute activity of brain regions. It can only detect difference of brain activity between several conditions. During the fMRI image acquisitions, the patient is therefore asked to alternatively perform several tasks or is stimulated to trigger several processes or emotions. Each of these conditions is repeated several times and can be separated by rest periods.The combination of these conditions is called a functional MRI paradigm. The stimuli are usually audio-visual but can involve more complex systems (odors, tastes,etc.). MR-compatible response pads are often used to get a feedback from the patient.

BOLD effect

The detection of brain areas which are used during a condition is based on the Blood Oxygenation Level Dependent (BOLD) effect, which creates a variation in the EPI images' signal, linked with the concentration oxy-/deoxy-hemoglobine in each area during each condition.

fMRI analysis

Unfortunately, this signal change is very low and cannot be directly detected. Therefore, advanced statistical methods (general linear model, for example) must be used to identify the voxels in which the signal varies according to the paradigm. Thresholded functional MRI activation maps can be overlaid in color on a high resolution anatomical MR image or displayed on a 3D reconstruction of the brain. Read more about fMRI analysis...

Clinical fMRI: Clinical applications of functional MRI

• Presurgical mapping of eloquent brain areas (motor, language,...)
• Assessment of plasticity after a brain injury

Read more about Clinical fMRI: Clinical applications of functional MRI

Research applications of functional MRI

• Mapping of complex functions (emotions, motor control, specialized language functions,...) in normal and pathological conditions
• Monitoring of treatment response
• Neuromarketing
• Lie detector
• Mind reading

Synonyms: functional MRI, functional magnetic resonance imaging, fMRI, functional imaging, brain mapping

Journals: Neuroimage, Human Brain Mapping

Interesting articles about fMRI

Description in other Languages:

• French: IRM fonctionnelle - IRMf