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 — reference:ft_datatype_parcellation [2018/08/23 14:43] (current) Line 1: Line 1: + =====  FT_DATATYPE_PARCELLATION ===== + + Note that this reference documentation is identical to the help that is displayed in MATLAB when you type "help ft_datatype_parcellation"​. + + <​html><​pre>​ + <​font color=green>​FT_DATATYPE_PARCELLATION​ describes the FieldTrip MATLAB structure for parcellated + cortex-based data and atlases. A parcellation can either be indexed or probabilistic + (see below). + + A parcellation describes the tissue types for each of the surface elements. + Parcellations are often, but not always labeled. A parcellatoin can be used to + estimate the activity from MEG data in a known region of interest. A surface-based + atlas is basically a very detailled parcellation with an anatomical label for each + vertex. + + An example of a surface based Brodmann parcellation looks like this + + pos: [8192x3] ​        ​positions of the vertices forming the cortical sheet + tri: [16382x3] ​       triangles of the cortical sheet + coordsys: '​ctf' ​           the (head) coordinate system in which the vertex positions are expressed + unit: '​mm' ​            the units in which the coordinate system is expressed + brodmann: [8192x1 uint8] ​  ​values from 1 to N, the value 0 means unknown + ​brodmannlabel:​ {Nx1 cell} + + An alternative representation of this parcellation is + + pos: [8192x3] ​          ​positions of the vertices forming the cortical sheet + tri: [16382x3] ​         triangles of the cortical sheet + coordsys: '​ctf' ​             the (head) coordinate system in which the vertex positions are expressed + unit: '​mm' ​              the units in which the coordinate system is expressed + ​Brodmann_Area_1:​ [8192x1 logical] ​  ​binary map representing the voxels belonging to the specific area + ​Brodmann_Area_2:​ [8192x1 logical] ​  ​binary map representing the voxels belonging to the specific area + ​Brodmann_Area_3:​ [8192x1 logical] ​  ​binary map representing the voxels belonging to the specific area + ... + + The examples above demonstrate that a parcellation can be indexed, i.e. consisting of + subsequent integer numbers (1, 2, ...) or probabilistic,​ consisting of real numbers + ranging from 0 to 1 that represent probabilities between 0% and 100%. An extreme case + is one where the probability is either 0 or 1, in which case the probability can be + represented as a binary or logical array. + + The only difference to the source data structure is that the parcellation structure + contains the additional fields xxx and xxxlabel. See <​font color=green>​FT_DATATYPE_SOURCE​ for further + details. + + Required fields: + - pos + + Optional fields: + - tri, coordsys, unit + + Deprecated fields: + - none + + Obsoleted fields: + - none + + Revision history: + (2012/​latest) The initial version was defined in accordance with the representation of + a voxel-based segmentation. + + See also <​font color=green>​FT_DATATYPE,​ <​font color=green>​FT_DATATYPE_SOURCE,​ <​font color=green>​FT_DATATYPE_SEGMENTATION​ +