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

  FT_DEFAULTS (ending with "s") sets some general settings in the global variable
  ft_default (without the "s") and takes care of the required path settings. You can
  call this function in your startup.m script. This function is also called at the
  begin of all FieldTrip functions.
  The global configuration defaults are stored in the global "ft_default" structure.
  The ft_checkconfig function that is called by many FieldTrip functions will merge
  these global configuration defaults with the cfg ctructure that you pass to 
  the FieldTrip function that you are calling.
  The global options and their default values are
    ft_default.checkconfig       = string, can be 'pedantic', 'loose', 'silent' (default = 'loose')
    ft_default.checkpath         = string, can be 'pedantic', 'once', 'no' (default = 'pedantic')
    ft_default.checksize         = number in bytes, can be inf (default = 1e5)
    ft_default.showcallinfo      = string, can be 'yes' or 'no' (default = 'yes')
    ft_default.trackconfig       = string, can be 'cleanup', 'report', 'off' (default = 'off')
    ft_default.trackusage        = false, or string with salt for one-way encryption of identifying information (by default this is enabled and an automatic salt is created)
    ft_default.trackdatainfo     = string, can be 'yes' or 'no' (default = 'no')
    ft_default.trackcallinfo     = string, can be 'yes' or 'no' (default = 'yes')
    ft_default.outputfilepresent = string, can be 'keep', 'overwrite', 'error' (default = 'overwrite')
    ft_default.debug             = string, can be 'display', 'displayonerror', 'displayonsuccess', 'save', 'saveonerror', saveonsuccess' or 'no' (default = 'no')
    ft_default.toolbox.signal    = string, can be 'compat' or 'matlab' (default = 'compat')
    ft_default.toolbox.stats     = string, can be 'compat' or 'matlab' (default = 'compat')
    ft_default.toolbox.images    = string, can be 'compat' or 'matlab' (default = 'compat')
  If you want to overrule these default settings, you can add something like this in your startup.m script
    global ft_default
    ft_default.option1 = value1
    ft_default.option2 = value2
  The toolbox option for signal, stats and images allows you to specify whether you
  want to use a compatible drop-in to be used for these MathWorks toolboxes, or the
  original version from MathWorks.  The default is 'compat', which has the advantage
  that you do not need a license for these toolboxes.