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 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 FT_DATATYPE, FT_DATATYPE_SOURCE, FT_DATATYPE_SEGMENTATION