Objective To study the change of frequency tuning in inferior collicular neurons when added weak noise forward masking.Methods We examined the changes in neuronal frequency tuning resulted from a weak white noise as forward masking relative to 5dB beyond minimum threshold (reMT+5) and different duration (40、60、80、100 ms) under free field stimulation conditions.Results Weak noise forward masking sharpens frequency tuning curves (FTCs) of most neurons (P