Ascending Inputs From Ventral Nucleus Of The Lateral Lemniscus Affect Acoustic Signal Detection Of Inferior Colliculus Neurons

The ventral nucleus of the lateral lemniscus (VNLL) is an important nucleus of the central auditory, which plays an important role in sound signal processing, auditory ascending transmission, and acoustic signal detection in inferior colliculus (IC) neurons. Under free field, research acoustic signal characteristic detection of in VNLL neurons of the mouse; under electrical stimulation VNLL condition, study the impact on IC neurons acoustic signal feature detection, the experimental results obtained are as follows:1. Two types of firing pattern were found in VNLL neurons:onset and sustained, the first spike latency (FSL) of onset neurons was shorter than the FSL of sustained neurons. When sound intensity increased, the FSL of onset neurons was unvaried while the FSL of sustained neurons was shortened, indicating that onset neurons have a precise timing characteristic. We also measured Q10and Q30of frequency tuning curve, there was no difference between onset and sustained neurons, suggesting that there was no correlation between firing pattern and frequency tuning. Three types of the rate-intensity function (RIF) were found in VNLL neurons, the proportion of monotonic RIF is largest, followed by the proportion of saturated RIF, the proportion of non-monotonic RIF is least. The dynamic range (DR) in onset neurons was shorter than the DR in sustained neurons, indicating the capability of intensity tuning was divergent between different firing patterns and this difference is related to the type of RIF. Furthermore, best frequency of VNLL neuron was negatively correlated with depth, suggesting that VNLL has frequency topologic organization.2. Under electrical stimulation VNLL condition, we recorded acoustic responses in85IC neurons, the proportion of inhibited is largest, followed by the proportion of unaffected, the proportion of facilitated is least. The depth of three types IC neurons was in order to reduce, the FSL in order to extend, and FSL difference between VNLL and three types IC neurons are also in order to extend, indicating the distribution of three types IC neurons is regional. We compared intensity tune during electrical stimulation VNLL, the RIF of inhibited IC neurons were inhibited, DR reduced, slope increased, suggesting that the capabilities of intensity tuning were enhanced by electrical stimulation VNLL. Further study show that three types RIF were all inhibited and the inhibited impact was gradually decreased with the sound intensity increasing. The RIF of unaffected IC neurons did not change significantly, indicating that the capabilities of intensity tuning were not enhanced by electrical stimulation VNLL. We also measured Q value of FTC in inhibited, unaffected and facilitated IC neurons, there was no difference during electrical stimulation, indicating that the sharpness of frequency tuning of IC neurons was mediated by nucleus other than VNLL.