Fig. 3.

Use of the standard separation analysis to determine the masked thresholds for two inferior colliculus neurons (A, B). Rate-versus-level functions are shown for So (filled circles) and Sπ (open squares) 500 Hz tones in the presence of noise in the same phase (No) at the two ears. The discharge rates over the first 10 dB of the rate-versus-level function were used to estimate the mean and SD of the discharge rates attributable to the noise alone. The standard separation values are plotted for each 1 dB step in tone level in (C, D). The criterion of a D value of 1.0 was used to determine the minimum sound level at which a response to the tone (either an increase or a decrease in the discharge rate) could be detected (i.e., the masked threshold). The masked thresholds are shown by the arrows in C andD, and these are replotted in the insetsof A and B.