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fMRI Ch 7
| Term | Definition |
|---|---|
| Oxygenated Hemoglobin (Hb) | Hemoglobin with attached oxygen; it is diamagnetic |
| Diamagnetic | Having the property of a weak repulsion from a magnetic field |
| Deoxygenated Hemoglobin (dHb) | Hemoglobin without attached oxygen; it is paramagnetic |
| Paramagnetic | Having the property of being attracted to a magnetic field, though with less concentration of magnetic flux than ferromagnetic objects |
| Magnetic Susceptibility | The intensity of magnetization of a substance when placed within a magnetic field |
| Blood-oxygenation-level dependent (BOLD) contrast | The difference in signal on T2-weighted images as a function of the amount of deoxygenated hemoglobin |
| Autoradiography | An invasive imaging technique that labels molecules using radioactive isotopes and the measures the concentration of those molecules by exposing slices of tissue to photographic emulsions |
| Balloon Model | A model of the interaction between changes in blood flow associated with neuronal activity |
| Hemodynamic Response (HDR) | The change in MR signal on T2 images following the local neuronal activity. The hemodynamic response results from a decrease in the amount of deoxygenated hemoglobin present within a voxel |
| Peak | The maximal amplitude of the hemodynamic response, occurring typically about 4 to 6 s following a short-duration event |
| Undershoot | The decrease in MR signal amplitude below baseline due to the combination of reduced blood flow and increased blood volume |
| Time course | The change in MR signal over a series of fMRI images |
| Epoch | A time segment extracted from a larger series of images, usually corresponding to the period in time surrounding an event of interest |
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dkbjornn
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