Statistical parametric mapping: Difference between revisions

Revision as of 02:26, 24 December 2020

Revision as of 18:12, 27 January 2021

Line 1:

{{Other uses|SPM (disambiguation){{!}}SPM}}

{{unreferencedmore citations needed|date=NovemberJanuary 20102021}}

'''Statistical parametric mapping''' ('''SPM''') is a [[statistical]] technique for examining differences in [[brain]] activity recorded during [[functional neuroimaging]] experiments. It was created by [[Karl Friston]]. It may alternatively refer to software created by the Wellcome Department of Imaging Neuroscience at [[University College London]] to carry out such analyses.

Line 16:

Images from the scanner may be pre-processed to remove noise or correct for sampling errors.

A study usually scans a subject several times. To account for the motion of the head between scans, the images are typically adjusted so voxels in each image correspond (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 multiple participants, each of whom have differently shaped brains. All are likely to have the same gross anatomy, saving minor differences in overall brain size, individual variation in topography of the [[gyri]] and [[Sulcus (neuroanatomy)|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, via ''[[spatial normalization]]''. Such normalization typically involves translation, rotation and scaling and nonlinear warping of the brain surface to match a standard template. Standard brain maps such as the [[Talairach coordinates|Talairach-Tournoux]] or templates from the [[Montréal Neurological Institute]] (MNI) allow researchers from across the world to compare their results.

Line 32:

[[Image:Functional magnetic resonance imaging.jpg|thumb|right|Brain activation from fMRI shown as patch of colour on MRI scan]]

Differences in measured brain activity can be represented in various ways.

They can be presented as a table, displaying coordinates that show the most significant differences in activity between tasks. Alternatively, differences in brain activity can be shown as patches of colour on a brain 'slice', with the colours representing the ___location of voxels with statistically significant differences between conditions. The color gradient is mapped to statistical values, such as t-values or z-scores. This creates an intuitive and visually appealing map of the relative statistical strength of a given area.

Differences in activity can 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 means of summarizing the total area of significant change in a given statistical comparison.