```
FT_SOURCEINTERPOLATE interpolates source activity or statistical maps onto the
voxels or vertices of an anatomical description of the brain. Both the functional
and the anatomical data can either describe a volumetric 3D regular grid, a
triangulated description of the cortical sheet or an arbitrary cloud of points.
The functional data in the output data will be interpolated at the locations at
which the anatomical data are defined. For example, if the anatomical data was
volumetric, the output data is a volume-structure, containing the resliced source
and the anatomical volume that can be visualized using FT_SOURCEPLOT or written to
file using FT_SOURCEWRITE.
The following scenarios are possible:
- Both functional data and anatomical data are defined on 3D regular grids, for
example with a low-res grid for the functional data and a high-res grid for the
anatomy.
- The functional data is defined on a 3D regular grid of source positions
and the anatomical data is defined on an irregular point cloud, which can be a
2D triangulated mesh.
- The functional data is defined on an irregular point cloud, which can be a 2D
triangulated mesh, and the anatomical data is defined on a 3D regular grid.
- Both the functional and the anatomical data are defined on an irregular
point cloud, which can be a 2D triangulated mesh.
- The functional data is defined on a low resolution 2D triangulated mesh and the
anatomical data is defined on a high resolution mesh, where the low-res vertices
form a subset of the high-res vertices. This allows for mesh based interpolation.
The algorithm currently implemented is so-called 'smudging' as it is also applied
by the MNE-suite software.
Use as
[interp] = ft_sourceinterpolate(cfg, source, anatomy)
[interp] = ft_sourceinterpolate(cfg, stat, anatomy)
where
source is the output of FT_SOURCEANALYSIS
stat is the output of FT_SOURCESTATISTICS
anatomy is the output of FT_READ_MRI or one of the FT_VOLUMExxx functions,
a cortical sheet that was read with FT_READ_HEADSHAPE, or a regular
3D grid created with FT_PREPARE_SOURCEMODEL.
and cfg is a structure with any of the following fields
cfg.parameter = string (or cell-array) of the parameter(s) to be interpolated
cfg.downsample = integer number (default = 1, i.e. no downsampling)
cfg.interpmethod = string, can be 'nearest', 'linear', 'cubic', 'spline', 'sphere_avg' or 'smudge' (default = 'linear for interpolating two 3D volumes, 'nearest' for all other cases)
The supported interpolation methods are 'nearest', 'linear', 'cubic' or 'spline'
for interpolating two 3D volumes onto each other. For all other cases the supported
interpolation methods are 'nearest', 'sphere_avg' or 'smudge'.
The functional and anatomical data should be expressed in the same
coordinate sytem, i.e. either both in MEG headcoordinates (NAS/LPA/RPA)
or both in SPM coordinates (AC/PC).
To facilitate data-handling and distributed computing you can use
cfg.inputfile = ...
cfg.outputfile = ...
If you specify one of these (or both) the input data will be read from a *.mat
file on disk and/or the output data will be written to a *.mat file. These mat
files should contain only a single variable, corresponding with the
input/output structure.
See also FT_READ_MRI, FT_READ_HEADSHAPE, FT_SOURCEPLOT, FT_SOURCEANALYSIS,
FT_SOURCEWRITE
```