Rate functions for the amplitude of neural responses are presented as a function of stimulus parameters, such as burst length, intensity, and stimulus power level. The data show that the rate functions depend on all of these parameters in a manner that does not allow for a simple description. Rate functions are also reported for noise bursts in the presence of various levels of steady masking noise. Near visual detection level these rate functions exhibit characteristics that are well accounted for by a model that deals with the overlapping of successive neural responses.