fMRI: Biological Basis and Experiment Design
Lecture 4
• History
• Basic mechanism
• Outstanding
questions
movie of steric conformations, from wikipedia.com
Basic BOLD
“... blood oxygenation level-dependent (BOLD) contrast: a change in the signal
strength of brain water protons produced by the paramagnetic effects of venous
blood deoxyhemoglobin.” –Ogawa et al. 1993
Signal inversely proportional to deoxyhemoglobin concentration
• CBF = cerebral blood flow
– increased CBF increases signal strength
• CBV = cerebral blood volume
– increased venous blood volume decreases signal strength
• CMRO2 = cerebral metabolic rate of oxygen
– increased CMRO2 decreases signal strength
Harrison, Harel et al., Cerebral Cortex 12:225 (2002)
Discussion papers
• “Spikes versus BOLD: what does neuroimaging tell us
about neuronal activity?”
– David Heeger, Alex Huk, Wilson Beisler & Duane Albrecht
– Nature Neuroscience 3(7):631.
• “Neurophysiological investigation of the basis of the fMRI
signal”
– Nikos Logothetis, Jon Pauls, Mark Augath, Torsten Trinath & Axel
Oeltermann
– Nature 412:150.
• “Separate spatial scales determine neural activitydependent changes in tissue oxygen within central visual
pathways,”
– Jeffrey Thompson, Matthew Peterson, Ralph Freeman
– Journal of Neuroscience 25(39)9046