Selective inhibition of weak forward masker with different durations on the acoustical responses of the inferior collicular neurons in the mouse
不同时程弱前掩蔽声对小鼠下丘神经元声反应的选择性抑制

To study the effects of forward masker sound with different durations on neuronal firing and rate-intensity function(RIF)of inferior colliculus(IC)neurons,a tone relative to 5 dB above minimum threshold(re MT 5 dB)at the characteristic frequency(CF)of recording neurons was used as forward masker sound under free field stimulation.The masker durations were 40,60,80,100 ms respectively.154 neurons were recorded and 104 neurons were examined under different masker durations.We found that there were three types of inhibition period of neuronal firing,i.e.,early-inhibition(41%),late-inhibition(9%)and whole-inhibition(50%).The inhibition period of 72(72%)neurons remained constant whereas that of a minority of the neurons(28%)altered when masker duration was changed.Among the 28 neurons,most of them tended to transform the late-inhibition into the early-inhibition or the whole-inhibition.Moreover,the RIFs of 54(58.06%)neurons changed as the masker duration increasing.Most monotonic RIFs were converted to saturated,and saturated to nonmonotonic RIFs.However,this transformation was not as regular as masker duration increasing.Our results suggest that the inhibitory influences of forward masking upon temporal and intensity domains of the acoustical responses of the IC neurons are not proportionate.The inhibitory input induced by forward masker with diverse durations might differentially modulate the response properties of IC neurons.