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

  FT_APPENDSPIKE combines continuous data (i.e. LFP) with point-process data
  (i.e. spikes) into a single large dataset. For each spike channel an
  additional continuos channel is inserted in the data that contains
  zeros most of the time, and an occasional one at the samples at which a
  spike occurred. The continuous and spike data are linked together using
  the timestamps.
  Use as
    [spike] = ft_appendspike(cfg, spike1, spike2, spike3, ...)
  where the input structures come from FT_READ_SPIKE, or as
    [data]  = ft_appendspike(cfg, data, spike1, spike2, ...)
  where the first data structure is the result of FT_PREPROCESSING
  and the subsequent ones come from FT_READ_SPIKE.