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{{Short description|Statistical technique}}
'''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 [[functional Magnetic Resonance Imaging|fMRI]] or [[Positron Emission Tomography|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.▼
{{Other uses|SPM (disambiguation){{!}}SPM}}
{{more citations needed|date=January 2021}}
▲'''Statistical parametric mapping'''
==Approach==
===Unit of measurement===
Functional neuroimaging
===Experimental design===
Researchers
To
===Image pre-processing===
Images from the
A study
Functional neuroimaging studies usually involve
▲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]].
Images
▲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 [[Sulcus (anatomy)|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.
▲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.
===Statistical comparison===
[[Parametric statistics|Parametric statistical]] models are assumed at each voxel, using the
Analyses may
Because many statistical tests are
===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. ▼
▲
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.▼
▲Differences in activity
==Software==
SPM is software written by the
▲ [[Image:FMRI.jpg|thumb|left|Brain activation from fMRI shown as patch of colour on MRI scan]]
▲SPM is software written by the [http://www.fil.ion.ucl.ac.uk 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]].
==See also==
* [[Functional integration (neurobiology)]]
▲* [[cognitive neuroscience]]
* [[
* [[
* [[
* [[Dynamic causal modelling]]
* [[Neuroimaging]]
* [[Analysis of Functional NeuroImages|AFNI]]
* [[FreeSurfer]]
* [[Computational anatomy toolbox]]
* [[FMRIB Software Library|FSL]]
==References==
{{reflist}}
==External links==
* [
* [http://www.mccauslandcenter.sc.edu/CRNL/ fMRI guide by Chris Rorden]
* [http://cogprints.org/6193/ Introduction to fMRI: experimental design and data analysis]
* [http://www.mrc-cbu.cam.ac.uk/Imaging/Common/ Cambridge Imagers] - Neuroimaging information and tutorials.
* [http://www.fil.ion.ucl.ac.uk/~mgray/Presentations/Buttons%20in%20SPM5.ppt Buttons in SPM5] PowerPoint presentation from the SPM for dummies course
* [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]]
[[Category:Computing in medical imaging]]
[[Category:Neuroimaging]]
[[Category:Neuroimaging software]]
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