Functional magnetic resonance imaging: Difference between revisions
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'''Functional magnetic resonance imaging''' (usually abbreviated fMRI<ref>The f is written in lowercase unless at the beginning of a sentence.</ref>) is used to measure activity in the [[brain]]. This neuroimaging technique is based on the principle that [[neuron]]s require blood to function, and so neural activity can be inferred by tracking [[blood]] flow. FMRI machines produce images of | '''Functional magnetic resonance imaging''' (usually abbreviated fMRI<ref>The f is written in lowercase unless at the beginning of a sentence.</ref>) is used to measure activity in the [[brain]]. This neuroimaging technique is based on the principle that [[neuron]]s require blood to function, and so neural activity can be inferred by tracking [[blood]] flow. FMRI machines produce images of neural activity in the brain based on the magnetic properties of blood. | ||
== BOLD signal == | |||
FMRI is primarily used to research the areas of the brain that are specialized for information processing. Studies have confirmed several previously known anatomically distinct areas in the visual cortex,<ref name="pmid1948051">{{cite journal |author=Belliveau JW, Kennedy DN, McKinstry RC, ''et al'' |title=Functional mapping of the human visual cortex by magnetic resonance imaging |journal=Science |volume=254 |issue=5032 |pages=716–9 |year=1991 |pmid=1948051}}</ref> the motor cortex,<ref name="pmid8433133">{{cite journal |author=Kim SG, Ashe J, Georgopoulos AP, ''et al'' |title=Functional imaging of human motor cortex at high magnetic field |journal=J. Neurophysiol. |volume=69 |issue=1 |pages=297–302 |year=1993 |pmid=8433133}}</ref> and language areas.<ref name="pmid8987760">{{cite journal |author=Binder JR, Frost JA, Hammeke TA, Cox RW, Rao SM, Prieto T |title=Human brain language areas identified by functional magnetic resonance imaging |journal=J. Neurosci. |volume=17 |issue=1 |pages=353–62 |year=1997 |pmid=8987760}}</ref> | It has been known since 1890 that the active areas of the brain use more blood than when they are inactive,<ref>Roy, C. & Sherrington, C. (1890). On the regulation of the blood supply of the brain. ''Journal of Physiology'' 11, 85-108.</ref> although it took until 1980 to develop a method of tracking this change.<ref>{{cite journal |author=Ogawa S, Lee TM, Nayak AS, Glynn P |title=Oxygenation-sensitive contrast in magnetic resonance image of rodent brain at high magnetic fields |journal=Magn Reson Med |volume=14 |issue=1 |pages=68–78 |year=1990 |pmid=2161986}}</ref> Red blood cells contain [[hemoglobin]], a protein which stores and transports oxygen throughout the body. Active neurons consume oxygen from hemoglobin for [[energy]]. Hemoglobin is oxygenated when it is carrying oxygen, and deoxygenated when is depleted. Oxyhemoglobin is paramagnetic, which means it slightly repels a magnetic field, while deoxyhemoglobin is diamagnetic, which means it is slightly magnetic. An fMRI machine is able to detect these changes in magnetic properties, and creates an image based on the blood-oxygen-level-dependent (BOLD) signal. | ||
== Uses == | |||
FMRI is primarily used to research the areas of the brain that are specialized for information processing. Studies have confirmed several previously known anatomically distinct areas in the visual cortex,<ref name="pmid1948051">{{cite journal |author=Belliveau JW, Kennedy DN, McKinstry RC, ''et al'' |title=Functional mapping of the human visual cortex by magnetic resonance imaging |journal=Science |volume=254 |issue=5032 |pages=716–9 |year=1991 |pmid=1948051}}</ref> the motor cortex,<ref name="pmid8433133">{{cite journal |author=Kim SG, Ashe J, Georgopoulos AP, ''et al'' |title=Functional imaging of human motor cortex at high magnetic field |journal=J. Neurophysiol. |volume=69 |issue=1 |pages=297–302 |year=1993 |pmid=8433133}}</ref> and language areas.<ref name="pmid8987760">{{cite journal |author=Binder JR, Frost JA, Hammeke TA, Cox RW, Rao SM, Prieto T |title=Human brain language areas identified by functional magnetic resonance imaging |journal=J. Neurosci. |volume=17 |issue=1 |pages=353–62 |year=1997 |pmid=8987760}}</ref> FMRI has been used for preoperative neurosurgery preparation, but is otherwise uncommon in a clinical setting. Some potential clinical applications are presymptomatic diagnosis, drug development, individualized therapy, and an understanding of function brain disorders.<ref name="pmid16924262">{{cite journal |author=Matthews PM, Honey GD, Bullmore ET |title=Applications of fMRI in translational medicine and clinical practice |journal=Nat. Rev. Neurosci. |volume=7 |issue=9 |pages=732–44 |year=2006 |pmid=16924262 |doi=10.1038/nrn1929}}</ref> | |||
== References == | == References == | ||
<references/> | <references/> | ||
Revision as of 15:39, 23 December 2007
Functional magnetic resonance imaging (usually abbreviated fMRI[1]) is used to measure activity in the brain. This neuroimaging technique is based on the principle that neurons require blood to function, and so neural activity can be inferred by tracking blood flow. FMRI machines produce images of neural activity in the brain based on the magnetic properties of blood.
BOLD signal
It has been known since 1890 that the active areas of the brain use more blood than when they are inactive,[2] although it took until 1980 to develop a method of tracking this change.[3] Red blood cells contain hemoglobin, a protein which stores and transports oxygen throughout the body. Active neurons consume oxygen from hemoglobin for energy. Hemoglobin is oxygenated when it is carrying oxygen, and deoxygenated when is depleted. Oxyhemoglobin is paramagnetic, which means it slightly repels a magnetic field, while deoxyhemoglobin is diamagnetic, which means it is slightly magnetic. An fMRI machine is able to detect these changes in magnetic properties, and creates an image based on the blood-oxygen-level-dependent (BOLD) signal.
Uses
FMRI is primarily used to research the areas of the brain that are specialized for information processing. Studies have confirmed several previously known anatomically distinct areas in the visual cortex,[4] the motor cortex,[5] and language areas.[6] FMRI has been used for preoperative neurosurgery preparation, but is otherwise uncommon in a clinical setting. Some potential clinical applications are presymptomatic diagnosis, drug development, individualized therapy, and an understanding of function brain disorders.[7]
References
- ↑ The f is written in lowercase unless at the beginning of a sentence.
- ↑ Roy, C. & Sherrington, C. (1890). On the regulation of the blood supply of the brain. Journal of Physiology 11, 85-108.
- ↑ Ogawa S, Lee TM, Nayak AS, Glynn P (1990). "Oxygenation-sensitive contrast in magnetic resonance image of rodent brain at high magnetic fields". Magn Reson Med 14 (1): 68–78. PMID 2161986.
- ↑ Belliveau JW, Kennedy DN, McKinstry RC, et al (1991). "Functional mapping of the human visual cortex by magnetic resonance imaging". Science 254 (5032): 716–9. PMID 1948051.
- ↑ Kim SG, Ashe J, Georgopoulos AP, et al (1993). "Functional imaging of human motor cortex at high magnetic field". J. Neurophysiol. 69 (1): 297–302. PMID 8433133.
- ↑ Binder JR, Frost JA, Hammeke TA, Cox RW, Rao SM, Prieto T (1997). "Human brain language areas identified by functional magnetic resonance imaging". J. Neurosci. 17 (1): 353–62. PMID 8987760.
- ↑ Matthews PM, Honey GD, Bullmore ET (2006). "Applications of fMRI in translational medicine and clinical practice". Nat. Rev. Neurosci. 7 (9): 732–44. DOI:10.1038/nrn1929. PMID 16924262. Research Blogging.