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+ | ===== FT_COMPUTE_LEADFIELD ===== | ||
+ | |||
+ | Note that this reference documentation is identical to the help that is displayed in MATLAB when you type "help ft_compute_leadfield". | ||
+ | |||
+ | <html><pre> | ||
+ | <a href=/reference/ft_compute_leadfield><font color=green>FT_COMPUTE_LEADFIELD</font></a> computes a forward solution for a dipole in a a volume | ||
+ | conductor model. The forward solution is expressed as the leadfield | ||
+ | matrix (Nchan*3), where each column corresponds with the potential or field | ||
+ | distributions on all sensors for one of the x,y,z-orientations of the | ||
+ | dipole. | ||
+ | |||
+ | Use as | ||
+ | [lf] = ft_compute_leadfield(dippos, sens, headmodel, ...) | ||
+ | with input arguments | ||
+ | dippos = position dipole (1*3 or Ndip*3) | ||
+ | sens = structure with gradiometer or electrode definition | ||
+ | headmodel = structure with volume conductor definition | ||
+ | |||
+ | The headmodel represents a volume conductor model, its contents | ||
+ | depend on the type of model. The sens structure represents a sensor | ||
+ | array, i.e. EEG electrodes or MEG gradiometers. | ||
+ | |||
+ | It is possible to compute a simultaneous forward solution for EEG and MEG | ||
+ | by specifying sens and grad as two cell-arrays, e.g. | ||
+ | sens = {senseeg, sensmeg} | ||
+ | headmodel = {voleeg, volmeg} | ||
+ | This results in the computation of the leadfield of the first element of | ||
+ | sens and headmodel, followed by the second, etc. The leadfields of the | ||
+ | different imaging modalities are subsequently concatenated. | ||
+ | |||
+ | Additional input arguments can be specified as key-value pairs, supported | ||
+ | optional arguments are | ||
+ | 'reducerank' = 'no' or number | ||
+ | 'normalize' = 'no', 'yes' or 'column' | ||
+ | 'normalizeparam' = parameter for depth normalization (default = 0.5) | ||
+ | 'weight' = number or 1xN vector, weight for each dipole position (default = 1) | ||
+ | 'backproject' = 'yes' (default) or 'no', in the case of a rank reduction | ||
+ | this parameter determines whether the result will be | ||
+ | backprojected onto the original subspace | ||
+ | |||
+ | The leadfield weight may be used to specify a (normalized) | ||
+ | corresponding surface area for each dipole, e.g. when the dipoles | ||
+ | represent a folded cortical surface with varying triangle size. | ||
+ | |||
+ | Depending on the specific input arguments for the sensor and volume, this | ||
+ | function will select the appropriate low-level EEG or MEG forward model. | ||
+ | The leadfield matrix for EEG will have an average reference over all the | ||
+ | electrodes. | ||
+ | |||
+ | The supported forward solutions for MEG are | ||
+ | single sphere (Cuffin and Cohen, 1977) | ||
+ | multiple spheres with one sphere per channel (Huang et al, 1999) | ||
+ | realistic single shell using superposition of basis functions (Nolte, 2003) | ||
+ | leadfield interpolation using a precomputed grid | ||
+ | boundary element method (BEM) | ||
+ | |||
+ | The supported forward solutions for EEG are | ||
+ | single sphere | ||
+ | multiple concentric spheres (up to 4 spheres) | ||
+ | leadfield interpolation using a precomputed grid | ||
+ | boundary element method (BEM) | ||
+ | |||
+ | See also <a href=/reference/ft_prepare_vol_sens><font color=green>FT_PREPARE_VOL_SENS</font></a>, <a href=/reference/ft_headmodel_asa><font color=green>FT_HEADMODEL_ASA</font></a>, <a href=/reference/ft_headmodel_bemcp><font color=green>FT_HEADMODEL_BEMCP</font></a>, | ||
+ | <a href=/reference/ft_headmodel_concentricspheres><font color=green>FT_HEADMODEL_CONCENTRICSPHERES</font></a>, <a href=/reference/ft_headmodel_dipoli><font color=green>FT_HEADMODEL_DIPOLI</font></a>, <a href=/reference/ft_headmodel_halfspace><font color=green>FT_HEADMODEL_HALFSPACE</font></a>, | ||
+ | <a href=/reference/ft_headmodel_infinite><font color=green>FT_HEADMODEL_INFINITE</font></a>, <a href=/reference/ft_headmodel_localspheres><font color=green>FT_HEADMODEL_LOCALSPHERES</font></a>, <a href=/reference/ft_headmodel_openmeeg><font color=green>FT_HEADMODEL_OPENMEEG</font></a>, | ||
+ | <a href=/reference/ft_headmodel_singleshell><font color=green>FT_HEADMODEL_SINGLESHELL</font></a>, <a href=/reference/ft_headmodel_singlesphere><font color=green>FT_HEADMODEL_SINGLESPHERE</font></a>, | ||
+ | <a href=/reference/ft_headmodel_halfspace><font color=green>FT_HEADMODEL_HALFSPACE</font></a> | ||
+ | </pre></html> | ||