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 — 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>​ + <​font color=green>​FT_DATATYPE_HEADMODEL​ 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:  + 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 -> openmeeg, + fem_simbio -> simbio, concentric -> concentricspheres. Deprecated the fields + that indicate the index of the innermost and outermost surfaces. + + See also <​font color=green>​FT_DATATYPE,​ <​font color=green>​FT_DATATYPE_COMP,​ <​font color=green>​FT_DATATYPE_DIP,​ <​font color=green>​FT_DATATYPE_FREQ,​ + <​font color=green>​FT_DATATYPE_MVAR,​ <​font color=green>​FT_DATATYPE_RAW,​ <​font color=green>​FT_DATATYPE_SOURCE,​ <​font color=green>​FT_DATATYPE_SPIKE,​ + <​font color=green>​FT_DATATYPE_TIMELOCK,​ <​font color=green>​FT_DATATYPE_VOLUME​ +