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Statistical parametric mapping or SPM is a statistical technique for examining differences in brain activity recorded during functional neuroimaging experiments using neuroimaging technologies such as fMRI or PET. It may also refer to a specific piece of software created by the Wellcome Department of Imaging Neuroscience (part of University College London) to carry out such analyses. For Wikipedia statistics, see m:Statistics Statistics is the science and practice of developing human knowledge through the use of empirical data expressed in quantitative form. ...
Human brain In animals, the brain (enkephale) (Greek for in the skull), is the control center of the central nervous system, responsible for behavior. ...
Functional neuroimaging is the use of neuroimaging technology to measure an aspect of brain function, often with a view to understanding the relationship between activity in certain brain areas and specific mental functions. ...
It has been suggested that this article or section be merged with functional neuroimaging. ...
Functional magnetic resonance imaging (fMRI) is the use of MRI to measure the haemodynamic response related to neural activity in the brain or spinal cord of humans or other animals. ...
Image of a typical positron emission tomography (PET) facility Positron emission tomography (PET) is a nuclear medicine medical imaging technique which produces a three-dimensional image or map of functional processes in the body. ...
Affiliations University of London Russell Group LERU EUA ACU Golden Triangle G5 Website http://www. ...
The statistical parametric mapping approach
Unit of measurement Functional neuroimaging, one type of 'brain scanning', involves the measurement of brain activity. The specific technique used to measure brain activity depends on the imaging technology being used (see fMRI and PET for examples). Regardless of which technology is used, the scanner produces a 'map' of the area being scanned that is represented as voxels. Each voxel typically represents the activity of a particular co-ordinate in three dimensional space. The exact size of a voxel will vary depending on the technology used, although fMRI voxels typically represent a volume of 27 mm3 (a cube with 3mm length sides). Functional Magnetic Resonance Imaging (or fMRI) describes the use of MRI to measure hemodynamic signals related to neural activity in the brain or spinal cord of humans or other animals. ...
Image of a typical positron emission tomography (PET) facility Positron emission tomography (PET) is a nuclear medicine medical imaging technique which produces a three-dimensional image or map of functional processes in the body. ...
A voxel (a portmanteau of the words volumetric and pixel) is a volume element, representing a value on a regular grid in three dimensional space. ...
Experimental design Researchers are often interested in examining brain activity linked to a specific psychological process or processes. An experimental approach to this problem might involve asking the question 'which areas of the brain are significantly more active when a person is doing task A compared to task B?'. Although each task might be designed to be identical, except for the aspect of behaviour under investigation, the brain is still likely to show changes in activity between tasks due to factors other than task differences (as the brain is involved with co-ordinating a whole range of parallel functions unrelated to the experimental task). Furthermore, the signal may contain noise from the imaging process itself.
To accommodate these random effects, and to highlight the areas of activity linked specifically to the process under investigation, statistics are used to look for the most significant difference above and beyond background brain activity. This involves a multi-stage process to prepare the data, and to subsequently analyse it using a statistical method known as the general linear model. The general linear model (GLM) is a statistical, linear model. ...
Image pre-processing Images from the brain scanner may be pre-processed before any statistical comparison takes place to remove noise or correct for sampling errors.
A study will usually scan a subject several times. To account for the motion of the head between scans, the images will usually be adjusted so each of the voxels in the images corresponds (approximately) to the same site in the brain. This is referred to as realignment or motion correction, see image realignment.
Functional neuroimaging studies usually involve several participants, who will have slightly differently shaped brains. All are likely to have the same gross anatomy, but there will be minor differences in overall brain size, individual variation in topography of the gyri and sulci of the cerebral cortex, and morphological differences in deep structures such as the corpus callosum. To aid comparisons, the 3D image of each brain is transformed so that superficial structures line up, a process known as spatial normalization. Such normalization typically involves not only translation and rotation, but also scaling and nonlinear warping of the brain surface to match a standard template. Standard brain maps such as the Talairach-Tournoux or templates from the Montréal Neurological Institute (MNI) are often used to allow researchers from across the world to compare their results. Grays FIG. 726– Lateral surface of left cerebral hemisphere, viewed from the side. ...
A sulcus (pl. ...
For other uses, see Cortex. ...
The corpus callosum is a structure of the mammalian brain in the longitudal fissure that connects the left and right cerebral hemispheres. ...
To meet Wikipedias quality standards and make it more accessible to a general audience, this article may require cleanup. ...
Founded in 1934 by Dr. Wilder Penfield with a $1. ...
Images are often smoothed (similar to the 'blur' effect used in some image-editing software) by which voxels are averaged with their neighbours, typically using a Gaussian filter or by wavelet transformation, to make the data less noisy. GAUSSIAN is a computational chemistry software program, first written by John Pople. ...
A wavelet is a kind of mathematical function used to divide a given function into different frequency components and study each component with a resolution that matches its scale. ...
Statistical comparison Parametric statistical models are assumed at each voxel, using the general linear model to describe the variability in the data in terms of experimental and confounding effects, and residual variability. Hypotheses expressed in terms of the model parameters are assessed at each voxel with univariate statistics. Parametric inferential statistical methods are mathematical procedures for statistical hypothesis testing which assume that the distributions of the variables being assessed belong to known parametrized families of probability distributions. ...
The general linear model (GLM) is a statistical, linear model. ...
Analyses may also be conducted to examine differences over a time series (i.e correlations between a task variable and brain activity in a certain area) using linear convolution models of how the measured signal is caused by underlying changes in neural activity. In statistics, signal processing, and econometrics, a time series is a sequence of data points, measured typically at successive times, spaced at (often uniform) time intervals. ...
In mathematics and, in particular, functional analysis, convolution is a mathematical operator which takes two functions f and g and produces a third function that in a sense represents the amount of overlap between f and a reversed and translated version of g. ...
Because many statistical tests are being conducted, adjustments have to be made to control for Type I errors (false positives) potentially caused by the comparison of levels of activity at a large number of voxels. In this case, a Type I error would result in falsely detecting background brain activity as activity related to the task. Adjustments are made, based on the number of resels in the image and the theory of continuous random fields in order to set a new criterion for statistical significance that adjusts for the problem of multiple comparisons. In statistical hypothesis testing, a Type I error consists of rejecting a null hypothesis that is true, in other words finding a result to have statistical significance when this has in fact happened by chance. ...
A resel is a resolution element - a concept used in image analysis. ...
In probability theory, let S = {X1, ..., Xn}, with the Xi in {0,1,...,G-1}, be a set of random variables on the sample space Ω={0,1,...,G-1}n, a probability measure π is a random field if . There exist several types of random fields, such as Markov...
In statistics, the multiple comparisons problem tests null hypotheses stating that the averages of several disjoint populations are equal to each other (homogeneous). ...
Graphical representations Differences in measured brain activity can be represented in a number of ways.
Most simply, they can be presented as a table, displaying co-ordinates that show the most significant differences in activity between tasks. However, differences in brain activity are more often shown as patches of colour on an MRI brain 'slice', with the colours representing the location of voxels that have shown statistically significant differences between conditions. The gradient of color is mapped to statistical values, such as t-values or z-scores. This creates an intuitive and visually appealing means of delineating the relative statistical strength of a given area of activation. Recently, an alternative approach has been suggested, in which the statistical map is combined with the map of the original difference in brain activity (or, more generally speaking, with the original contrast) and colorcodes are attributed to the latter.
Differences in activity may also be represented as a 'glass brain', a representation of three outline views of the brain as if it were transparent. Only the patches of activation are visible as areas of shading. This is useful as a quick means of summarizing the total area of significant change in a given statistical comparison.
 Brain activation from fMRI shown as patch of colour on MRI scan Sample fMRI data This example of fMRI data shows regions of activation including primary visual cortex (V1, BA17), extrastriate visual cortex and lateral geniculate body in a comparison between a task involving a complex moving visual stimulus and rest condition (viewing a black screen). ...
Sample fMRI data This example of fMRI data shows regions of activation including primary visual cortex (V1, BA17), extrastriate visual cortex and lateral geniculate body in a comparison between a task involving a complex moving visual stimulus and rest condition (viewing a black screen). ...
SPM software SPM is software written by the Wellcome Department of Imaging Neuroscience at University College London to aid in the analysis of functional neuroimaging data. It is written using MATLAB and is distributed as free software. Affiliations University of London Russell Group LERU EUA ACU Golden Triangle G5 Website http://www. ...
Not to be confused with Matlab Upazila in Chandpur District, Bangladesh. ...
Free software is software that can be used, studied, and modified without restriction, and which can be copied and redistributed in modified or unmodified form either without restriction, or with restrictions only to ensure that further recipients can also do these things. ...
See also The field of cognitive neuroscience concerns the scientific study of the neural mechanisms underlying cognition and is a branch of neuroscience. ...
Functional magnetic resonance imaging (fMRI) is the use of MRI to measure the haemodynamic response related to neural activity in the brain or spinal cord of humans or other animals. ...
Functional neuroimaging is the use of neuroimaging technology to measure an aspect of brain function, often with a view to understanding the relationship between activity in certain brain areas and specific mental functions. ...
The general linear model (GLM) is a statistical, linear model. ...
It has been suggested that this article or section be merged with functional neuroimaging. ...
Analysis of Functional NeuroImages (AFNI) is an open source environment for processing and displaying functional MRI data—a technique for mapping human brain activity. ...
FreeSurfer is an MRI brain imaging software package developed by the Athinoula A. Martinos Center for Biomedical Imaging at Massachusetts General Hospital and CorTechs, Inc. ...
Example FSL GUIs The FMRIB Software Library (FSL) is a software library containing image analysis and statistical tools for functional, structural and diffusion MRI brain imaging data. ...
External links - Wikibooks SPM Wikibook.
- SPM software and documentation from the Wellcome Department of Imaging Neuroscience.
- Cambridge Imagers - Neuroimaging information and tutorials.
- Buttons in SPM5 PowerPoint presentation from the SPM for dummies course
- SPM-Information to include in papers
- ISAS (Ictal-Interictal SPECT Analysis by SPM) - Yale University
- AutoSPM: Automated SPM for Surgical Planning
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