Reference Work Entry

Encyclopedia of Autism Spectrum Disorders

pp 465-466

Blood-Oxygen-Level-Dependent (BOLD) Signal

  • Kevin A. PelphreyAffiliated withChild Study Center, Yale University School of Medicine Email author 


Blood-oxygen-level dependence


Blood-oxygen-level-dependent (BOLD) signal is the magnetic resonance imaging (MRI) contrast of blood deoxyhemoglobin. Seiji Ogawa and his colleagues first discovered this intrinsic contrast mechanism in 1990. Neurons do not store internal reserves of glucose and oxygen, which are essential to their proper function. Increases in neuronal activity, typically in response to a demand for information processing, require more glucose and oxygen to be rapidly delivered via the blood stream. Via this hemodynamic response, blood releases glucose and oxygen to active neurons at a faster rate relative to inactive neurons. This results in a surplus of oxyhemoglobin localized to the active area, giving rise to a measureable change in the local ration of oxy- to deoxyhemoglobin, thus providing a localizable marker of activity for MRI.

See Also

Event-Related Functional Magnetic Resonance Imaging (MRI)

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