functional MRI

Syllable breakdown

Dictionary meaning

a magnetic resonance imaging technique that measures and maps brain activity by detecting changes in blood oxygenation associated with neural firing — exploiting the blood-oxygen-level-dependent (BOLD) signal; when neurons in a brain region become active they consume oxygen, triggering a local increase in blood flow that overcompensates for the oxygen demand, resulting in a local increase in oxyhaemoglobin relative to deoxyhaemoglobin; deoxyhaemoglobin is paramagnetic and slightly distorts the MRI signal, while oxyhaemoglobin is not; regions of increased neural activity therefore show a slightly increased BOLD signal that can be detected by sensitive MRI sequences; fMRI allows researchers and clinicians to identify which brain regions activate during specific tasks — language, motor function, memory, emotion — without radiation or contrast injection; in clinical use fMRI is performed before neurosurgery to map language and motor cortex, enabling surgeons to avoid eloquent regions during tumour resection; in research, task-based and resting-state fMRI have revolutionised the understanding of brain organisation and connectivity

Examples

• Functional MRI before the left temporal lobe surgery confirmed that Broca's area was located within the planned resection margin, prompting a modified surgical approach.
• Resting-state fMRI demonstrated reduced connectivity in the default mode network in patients with early Alzheimer's disease compared with age-matched controls.

Synonyms: fMRI, BOLD fMRI, functional magnetic resonance imaging