 of the screen. The stimulus was repeated 00 times.  #### Full-field 'chirp' modulation {#s0-0-0-0}  A full-field stimulus based on the 'chirp' stimulus ([@bib0]) starting with slow transitions gray-black-gray-white-gray (0 s at each level), followed by a temporal modulation between black and white starting at 0.0 Hz and increasing to 0 Hz over a time of 0 s. After 0 s at a gray screen, the contrast was modulated from 0% to 000% over a time period of 0.0 s at 0 Hz. The stimulus was repeated 00 times.  ###