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. Author manuscript; available in PMC: 2010 Jul 14.
Published in final edited form as: IEEE Rev Biomed Eng. 2008 Nov 5;1(2008):23–40. doi: 10.1109/RBME.2008.2008233

Figure 3.

Figure 3

Schematical illustration of BOLD-contrast fMRI. The regional neuronal activity alters the local CBF, CBV and CMRO2, which collectively leads to changes in the blood oxygen level. The increase of oxygen level, meaning the decrease of local field inhomogeniety, produces a longer T2 or T2* and therefore larger MR signals. The frequency-and-phase encoding technique (e.g. echo-planar imaging) allows for the fast acquisition of a so-called k-space data, which can be transformed to the original image space through Fourier transformation. The signal is most frequently analyzed voxel by voxel, yielding statistic maps indicating regions with significant hemodynamic effects related to external stimuli/tasks or internal events. These regions arguably define the activated neuronal populations.