Glossary

block design Experimental design for functional neuroimaging in which an attempt is made to put the subject's brain in a steady state of activity by using the same type of task for an extended period of time (typically 20-60 sec) and then comparing the brain activation during that block with other blocks that use a different task.

blood oxygen level dependent (BOLD) Refers to a general method of magnetic resonance imaging (MRI) for detecting changes in the nuclear magnetic resonance (NMR) signal that are caused by the varying concentration of deoxyhemoglobin, locally, in the blood near a part of the brain.

event-related design Experimental design for functional neuroimaging in which individual, brief (typically 1-2 sec in duration) stimuli of different types are presented in random order, and where the evoked responses for many such trials of a given type are averaged together to detect a measureable response.

flow via alternating inversion recovery (FAIR) Refers to a specific method of MRI for detecting changes in the NMR signal that are caused by the varying flow, locally, of blood in arteries near a part of the brain.

functional magnetic resonance imaging (fMRI) The use of MRI

to detect changes in blood flow and blood oxygenation associated with local changes in neuronal activity in the brain.

gradient magnets Part of the technology of MRI used for supplying strong, operator-controlled linear gradients of magnetic field to enable the generation and detection of the NMR signal associated with a specific point in three-dimensional space.

hemodynamics Changes in the properties (volume, flow rate, and chemical composition) of blood over time.

magnetic resonance imaging (MRI) The use of a variety of operator-controlled electromagnetic fields to generate a NMR signal that can be associated with a particular point in space.

nuclear magnetic resonance (NMR) The physical phenomenon of absorption and reemission of electromagnetic energy associated with the quantum mechanical spin and magnetic field of the nuclei of some atoms.

principle component analysis (PCA) The re-representation of multidimensional data into a collection of components (sometimes called eigenimages and eigenvectors) via an algorithm that accounts for the most variance by the first principal component, the second most by the second component, etc.

retinotopy The regular spatial arrangement of the receptive fields of cortical neurons in many parts of the visual cortex that follows, in a systematic way, the two-dimensional spatial arrangement of the retina.

talairach coordinates The most widely used convention for orienting and scaling human brains to facilitate the averaging and/ or comparing of data across multiple subjects.

Functional magnetic resonance imaging (fMRI) refers to the use of the technology of magnetic resonance imaging (MRI) to detect the localized changes in blood flow and blood oxygenation that occur in the brain in response to neural activity. This article presents the basics of fMRI-based research, including the physical and biophysical bases of the signals, the current

Encyclopedia of the Human Brain Volume 2

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developments in experimental design and data analysis, and other practical considerations attendant to the technique, and also provides an overview of the broad range of scientific and clinical questions to which fMRI is being applied.

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