Differences

This shows you the differences between two versions of the page.

Link to this comparison view

reference:ft_datatype_headmodel [2018/08/23 14:43]
reference:ft_datatype_headmodel [2018/08/23 14:43] (current)
Line 1: Line 1:
 +=====  FT_DATATYPE_HEADMODEL =====
 +
 +Note that this reference documentation is identical to the help that is displayed in MATLAB when you type "help ft_datatype_headmodel"​.
 +
 +<​html><​pre>​
 +  <a href=/​reference/​ft_datatype_headmodel><​font color=green>​FT_DATATYPE_HEADMODEL</​font></​a>​ describes the FieldTrip MATLAB structure for a volume
 +  conduction model of the head that can be used for forward computations of
 +  the EEG potentials or the MEG fields. The volume conduction model represents
 +  the geometrical and the conductive properties of the head. These determine
 +  how the secondary (or impressed) currents flow and how these contribute to
 +  the model potential or field.
 + 
 +  A large number of forward solutions for the EEG and MEG are supported
 +  in FieldTrip, each with its own specification of the MATLAB structure that
 +  describes the volume conduction model of th ehead. It would be difficult to
 +  list all the possibilities here. One common feature is that the volume
 +  conduction model should specify its type, and that preferably it should
 +  specify the geometrical units in which it is expressed (e.g. mm, cm or m).
 + 
 +  An example of an EEG volume conduction model with 4 concentric spheres is:
 + 
 +  headmodel =
 +         r: [86 88 94 100]
 +         c: [0.33 1.00 0.042 0.33]
 +         o: [0 0 0]
 +      type: '​concentricspheres'​
 +      unit: '​mm'​
 + 
 +  An example of an MEG volume conduction model with a single sphere fitted to
 +  the scalp with its center 4 cm above the line connecting the ears is:
 + 
 +  headmodel =
 +         r: [12]
 +         o: [0 0 4]
 +      type: '​singlesphere'​
 +      unit: '​cm'​
 + 
 +  For each of the methods XXX for the volume conduction model, a corresponding
 +  function FT_HEADMODEL_XXX exists that contains all specific details and
 +  references to literature that describes the implementation.
 + 
 +  Required fields:
 +    - type
 + 
 +  Optional fields:
 +    - unit
 + 
 +  Deprecated fields:
 +    - inner_skull_surface,​ source_surface,​ skin_surface,​ source, skin
 + 
 +  Obsoleted fields:
 +    - &​lt;​none specified&​gt;​
 + 
 +  Revision history:
 + 
 +  (2015/​latest) Use the field name "​pos"​ instead of "​pnt"​ for vertex positions.
 + 
 +  (2014) All numeric values are represented in double precision.
 + 
 +  (2013) Always use the field "​cond"​ for conductivity.
 + 
 +  (2012) Use consistent names for the volume conductor type in the structure, the
 +  documentation and for the actual implementation,​ e.g. bem_openmeeg -&gt; openmeeg,
 +  fem_simbio -&gt; simbio, concentric -&gt; concentricspheres. Deprecated the fields
 +  that indicate the index of the innermost and outermost surfaces.
 + 
 +  See also <a href=/​reference/​ft_datatype><​font color=green>​FT_DATATYPE</​font></​a>,​ <a href=/​reference/​ft_datatype_comp><​font color=green>​FT_DATATYPE_COMP</​font></​a>,​ <a href=/​reference/​ft_datatype_dip><​font color=green>​FT_DATATYPE_DIP</​font></​a>,​ <a href=/​reference/​ft_datatype_freq><​font color=green>​FT_DATATYPE_FREQ</​font></​a>,​
 +  <a href=/​reference/​ft_datatype_mvar><​font color=green>​FT_DATATYPE_MVAR</​font></​a>,​ <a href=/​reference/​ft_datatype_raw><​font color=green>​FT_DATATYPE_RAW</​font></​a>,​ <a href=/​reference/​ft_datatype_source><​font color=green>​FT_DATATYPE_SOURCE</​font></​a>,​ <a href=/​reference/​ft_datatype_spike><​font color=green>​FT_DATATYPE_SPIKE</​font></​a>,​
 +  <a href=/​reference/​ft_datatype_timelock><​font color=green>​FT_DATATYPE_TIMELOCK</​font></​a>,​ <a href=/​reference/​ft_datatype_volume><​font color=green>​FT_DATATYPE_VOLUME</​font></​a>​
 +</​pre></​html>​