We have performed dielectric hole burning experiments on supercooled glycerol at frequencies up to five decades above the peak frequency of the dielectric loss. While most observations of heterogeneous dynamics refer to the slower than average relaxation times, this study confirms the existence of independent relaxation time scales across the high frequency wing of the relaxation time distribution. In this short time regime, the persistence time of the spectrally selective modifications is solely a matter of the burn frequency and no longer determined by the structural relaxation time. For a fixed value of the burn field, the amplitudes of the relaxation pattern changes measured along the log t scale (horizontal holes) are independent of the burn frequency omega(b) and dielectric loss epsilon"(omega(b)). This latter feature is observed in a range of burn frequencies which exceed the loss peak frequency by a factor of 10 to 3x10(5), where epsilon"(omega(b)) varies between 16 and 0.17. (C) 2003 American Institute of Physics.