Note that this reference documentation is identical to the help that is displayed in MATLAB when you type “help ft_appendsource”.

  FT_APPENDSOURCE concatenates multiple volumetric source reconstruction data
  structures that have been processed seperately.
 
  If the source reconstructions were computed for different ROIs or different slabs
  of a regular 3D grid (as indicated by the source positions), the data will be
  concatenated along the spatial dimension.
 
  If the source reconstructions were computed on the same source positions, but for
  different frequencies and/or latencies, e.g. for time-frequency spectrally
  decomposed data, the data will be concatenared along the frequency and/or time
  dimension.
 
  Use as
    combined = ft_appendsource(cfg, source1, source2, ...)
 
  See also FT_SOURCEANALYSIS, FT_DATATYPE_SOURCE, FT_APPENDDATA, T_APPENDTIMELOCK,
  FT_APPENDFREQ