Functional Magnetic Resonance Imaging (fMRI)
Definition
Functional magnetic resonance imaging (fMRI) is a technique for measuring neural activity, by detecting the hemodynamic changes in blood oxygenation and blood flow in response to neural activity, based on blood-oxygenation-level-dependent (BOLD) effect.
Description
Blood-oxygen-level dependent (BOLD) effect is the MRI contrast originated from blood deoxyhemoglobin in the tissue, first discovered by Ogawa, Lee, Kay, and Tank (1990) (Ogawa, Lee, Nayak, & Glynn, 1990; Ogawa et al., 1992). This method depends on the differential susceptibility between deoxyhemoglobin and oxyhemoglobin. Hemoglobin is diamagnetic when oxygenated but paramagnetic when deoxygenated (=deoxyhemoglobin). Therefore, magnetic resonance (MR) signal of blood is slightly different depending on the level of oxygenation. Higher BOLD signal intensities arise from increases in the concentration of oxygenated hemoglobin since the blood magnetic susceptibility more closely matches the tissue magnetic...
References and Readings
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