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

  FT_SPIKE_MAKETRIALS converts raw timestamps in a SPIKE structure to spike
  times that are relative to an event trigger in an SPIKE structure. This
  is a preprocessing step to use functions such as FT_SPIKE_PSTH.
  The main function of FT_SPIKE_MAKETRIALS is to create the field
  spike.time and spike.trial, which contain the trial numbers in which the
  spikes were recorded, and the onset and offset of the trial relative to
  trigger time t = 0.
  Use as
    [spike] = ft_spike_maketrials(cfg,spike)
      spike: The raw spike datatype, obtained from FT_READ_SPIKE
    cfg.trl  = is an nTrials-by-M matrix, with at least 3 columns:
      Every row contains start (col 1), end (col 2) and offset of the event
      trigger in the trial in timestamp or sample units (cfg.trlunit). 
      For example, an offset of -1000 means that the trigger (t = 0 sec) 
      occurred 1000 timestamps or samples after the
      trial start.
      If more columns are added than 3, these are used to construct the
      spike.trialinfo field having information about the trial.
      Note that values in cfg.trl get inaccurate above 2^53 (in that case 
      it is better to use the original uint64 representation)
    cfg.trlunit = 'timestamps' (default) or 'samples'. 
      If 'samples', cfg.trl should 
      be specified in samples, and cfg.hdr = data.hdr should be specified.
      This option can be used to reuse a cfg.trl that was used for
      preprocessing LFP data. 
      If 'timestamps', cfg.timestampspersecond should be
      specified, but cfg.hdr should not.
    cfg.hdr     = struct, should be specified if cfg.trlunit = 'samples'.
      This should be specified as cfg.hdr = data.hdr where data.hdr
      contains the subfields data.hdr.Fs (sampling frequency of the LFP),
      data.hdr.FirstTimeStamp, and data.hdr.TimeStampPerSecond.
    cfg.timestampspersecond = number of timestaps per second (for
      Neuralynx, 1000000 for example). This can be computed for example from
      the LFP hdr (cfg.timestampspersecond = data.hdr.Fs*data.hdr.TimeStampPerSecond)
      or is a priori known.
  Outputs appended to spike:
    spike.time                  = 1-by-nUnits cell array, containing the spike times in
                                  seconds relative to the event trigger.
    spike.trial                 = 1-by-nUnits cell array, containing the trial number for
                                  every spike telling in which trial it was recorded.
    spike.trialtime             = nTrials-by-2 matrix specifying the start and end of
                                  every trial in seconds.
    spike.trialinfo             = contains trial information