page_title: Functional magnetic resonance imaging
hierarchical_section_title: Functional magnetic resonance imaging
caption_attribution_description: Version 8.25 from the Textbook OpenStax Anatomy and Physiology Published May 18, 2016
context_page_description: Functional magnetic resonance imaging or functional MRI measures brain activity by detecting changes associated with blood flow. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area of the brain is in use, blood flow to that region also increases.
  The primary form of fMRI uses the blood-oxygen-level dependent contrast, discovered by Seiji Ogawa in 1990. This is a type of specialized brain and body scan used to map neural activity in the brain or spinal cord of humans or other animals by imaging the change in blood flow related to energy use by brain cells. Since the early 1990s, fMRI has come to dominate brain mapping research because it does not require people to undergo injections or surgery, to ingest substances, or to be exposed to ionizing radiation. This measure is frequently corrupted by noise from various sources; hence, statistical procedures are used to extract the underlying signal. The resulting brain activation can be graphically represented by color-coding the strength of activation across the brain or the specific region studied.
context_section_description: Functional magnetic resonance imaging or functional MRI (fMRI) measures brain activity by detecting changes associated with blood flow. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area of the brain is in use, blood flow to that region also increases.
  The primary form of fMRI uses the blood-oxygen-level dependent (BOLD) contrast, discovered by Seiji Ogawa in 1990. This is a type of specialized brain and body scan used to map neural activity in the brain or spinal cord of humans or other animals by imaging the change in blood flow (hemodynamic response) related to energy use by brain cells. Since the early 1990s, fMRI has come to dominate brain mapping research because it does not require people to undergo injections or surgery, to ingest substances, or to be exposed to ionizing radiation.  This measure is frequently corrupted by noise from various sources; hence, statistical procedures are used to extract the underlying signal.  The resulting brain activation can be graphically represented by color-coding the strength of activation across the brain or the specific region studied.  The technique can localize activity to within millimeters but, using standard techniques, no better than within a window of a few seconds. Other methods of obtaining contrast are arterial spin labeling and diffusion MRI. The latter procedure is similar to BOLD fMRI but provides contrast based on the magnitude of diffusion of water molecules in the brain.
  In addition to detecting BOLD responses from activity due to tasks/stimuli, fMRI can measure resting state fMRI, or taskless fMRI, which shows the subjects' baseline BOLD variance.  Since about 1998 studies have shown the existence and properties of the default mode network (DMN), aka 'Resting State Network' (RSN), a functionally connected neural network of apparent 'brain states'.
  fMRI is used in research, and to a lesser extent, in clinical work.  It can complement other measures of brain physiology such as EEG and NIRS.  Newer methods which improve both spatial and time resolution are being researched, and these largely use biomarkers other than the BOLD signal.  Some companies have developed commercial products such as lie detectors based on fMRI techniques, but the research is not believed to be developed enough for widespread commercialization.
caption: An fMRI image with yellow areas showing increased activity compared with a control condition.
exif: {"Image Orientation": "Horizontal (normal)"}