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==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 [[Positron Emission Tomography|PET]] for examples). Regardless of which technology is used, the scanner produces a 'map' of the area being scanned that is represented as [[voxel]]s. Each voxel typically represents the activity of a particular coordinate 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
===Experimental design===
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[[Parametric statistics|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.
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.
Because many statistical tests are being conducted, adjustments have to be made to control for [[Type I error]]s (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 [[resel]]s in the image and the theory of continuous [[random field]]s in order to set a new criterion for statistical significance that adjusts for the problem of [[multiple comparisons]].
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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.
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* [[FMRIB Software Library|FSL]]
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{{unreferenced|date=November 2010}}
==External links==
* [[b:SPM|Wikibooks]] SPM Wikibook.
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* [http://spect.yale.edu ISAS (Ictal-Interictal SPECT Analysis by SPM)] - Yale University
* [http://www.imagilys.com/autospm.html AutoSPM: Automated SPM for Surgical Planning]
[[Category:Biostatistics]]
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