Functional Magnetic Resonance Imaging (fMRI)

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 seconds), and then comparing the brain activation during that block with other blocks which use a different task. BOLD (Blood Oxygen Level Dependent): Refers to a general method of MRI for detecting changes in the 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 seconds 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. FAIR (Flow via Alternating Inversion Recovery): 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. fMRI (Functional Magnetic Resonance Imaging): 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 specfic point in three dimensional space. Hemodynamics: Changes in the properties (volume, flow rate, chemical composition) of blood, over time. MRI (Magnetic Resonance Imaging): The use of a variety of operator-controlled electro-magnetic fields to generate an NMR signal that can be associated with a particular point in space. NMR (Nuclear Magnetic Resonance): The physical phenomenon of absorption and re-emission of electromagnetic energy associated with the quantum mechanical spin and magnetic field of the nuclei of some atoms. PCA (Principle Component Analysis): 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 mulitple subjects.