An example of the fast periodic visual stimulation (FPVS) used in EEG to measure visual discirmination. A change of facial identity appears every 5 stimuli in this train of stimulation at 5.88 He. From:
Liu-Shuang, J., Norcia, A.M., Rossion, B. (2014). An objective index of individual face discrimination in the right occipito-temporal cortex by means of fast periodic visual stimulation. Neuropsychologia, 52, 57-72. [PDF]