Spike rate (SR) or spike counts and first spike latency (FSL) both are the parameters to evaluate responses of a neuron to sound amplitude and frequency,the basic parameters of acoustic stimulus.But,it is unknown that which one is better,for the systematic comparison between firing rate and FSL representing amplitude and frequency is scarce.This study systematically compared SR with FSL in accuracy and reliability of representation of these two parameters in mouse inferior colliculus.The results showed that:1.FSL was more efficient,precise and invariable than SR in representing amplitude and frequency and independent with SR,by quantitative statistic analysis and comparison of the quality of FSL and SR functions as amplitude or frequency.2.No paradoxical or constant latency neuron was found in the inferior colliculus of mouse.3.The monotonicity character of a neuron at its characteristic frequency (CF) could change with variation of acoustic frequency.The results strongly suggest that FSL is much better than spike rate or count in representation of acoustic amplitude and frequency within a neuron and would be a parameter to evaluate response to amplitude and frequency instead of spike rate or count,at least in mouse inferior colliculus,and that nonmonotonic response of auditory neurons would be derived from self-inhibition.