• activated: Boolean variable that establishes whether the stimulus is active or not.
  Useful when you have stimuli that should be presented in some trials and not presented in other trials.
  Use this variable to control the presence of the stimulus rather than using contrast = 0 or volume = 0 or other workarounds.
  Making the stimulus inactive is the only way to make sure neither CPU or GPU cycles are used to compute the stimulus. Integer value 0 or 1.
  
  
• start: Time at which the stimulus begins, measured from the start of the scene. Time property.
  
  
• duration: Duration of the stimulus. By default is set to 1000 seconds. Time property.