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psy400ch11p264-273
Magnetic Resonance Imaging
| Term | Definition |
|---|---|
| Magnetic resonance imaging (MRI) | uses powerful magnets to create images of anatomical structures in the brain. |
| Tesla (T): A measure of the strength of a magnetic field produced | by a magnet. Higher numbers indicate a stronger magnetic field. |
| Radiofrequency pulse: A short burst of a high wavelength, low-energy electromagnetic wave | that is produced by radio frequency coils in a magnetic resonance Imaging machine to alter the alignment of protons. |
| Relaxation: A measure used with magnetic resonance imaging that assesses the time it takes for | protons to return to their original state following a radio frequcncy pulse that altered their alignment |
| Radio frequency coils: Part of the magnetic resonance imaging machine that is used to produce radio frequency pulses. They | are also used to measure the energy given off by protons as they return to the state they were in prior to the radio frequency pulse |
| A Tl-weighted image is produced | when energy is emitted as the protons recover their original magnetization |
| In a Tl-weighted image tissues with high fat-content, such as the white matter of the brain, | appear bright, whereas sections of the brain filled with water appear dark |
| T2-weighted images capture energy emitted | as excessive spin (rather than magnetization) induced by the radio frequency pulse returns to the steady state. |
| T2-weighted images images have the | opposite contrast to T1 images |
| Functional magnetic resonance imaging (fMRI) | measures changes in blood flow, enabling researchers to obtain images of the brain while the brain processes information |
| Hemodynamic response: Changes in blood flow in the brain. | Increased blood flow to regions of the brain is associated with increased activity in that brain region |
| Voxels: In functional magnetic resonance imaging, | the smallest volume for which it is possible to compute a blood oxygen level dependent response |
| BOLD response: Blood oxygen level dependent response. Oxygenated and deoxygenated blood have different magnetic | properties. Higher levels of oxygenated blood compared with deoxygenated blood are found in brain regions that are active. |
| Motion artifacts | Data that are caused by the movement of the participant rather than a response to the stimuli of interest |
| Data map | A region in an fMRl image that shows BOLD changes correlated with changes in activation pattern. |
| Anterior cingulate | processes aversive states—for example, it is active when people make errors, experience pain, and exert hard mental effort |
| Diffusion-weighted Imaging (DWI) or Diffusion-weighted magnetic resonance imaging | MRI machine measures the diffusion of water molecules in different brain regions, able to identify pathways in the brain |
| Brain water motion is referred to as diffusion, and | rates of diffusion differ as a function of the type of brain tissue involved. |
| "passive listening paradigm," which involves capturing sounds | just as they were produced in a normal situation |
| Tractography | A three-dimensional modeling technique used to visualize the neural pathways. |
| Mean diffusion | A measure of how fast water molecules move, or diffuse, through brain regions. |
| Fractional anisotropy | A measure of the spatial pattern of diffusion. Basically, it describes whether diffusion is occurring equally in all directions or is greater in one direction or another |
| Near-infrared spectroscopy (NIRS): A neuroimaging technique for assessing brain function; | near-infrared light is shone through the scalp using optical fibers that are placed in a cap and reflected back to detectors in the cap |
| NIRS basically measures the same information that | fMRI does, but NIRS systems cheaper. Also the participant does not need to keep his or her head perfectly still |
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james22222222