Asending Inputs From Dorsal Nuclei Of Lateral Lemniscus Affect Acoustic Signal Detection Of Inferior Collicular Neurons

Inferior colliculus(IC) are important in the auditory system. Inhibitory input from dorsal nuclei of lateral lemniscus play an important role in shaping auditory responses. In this research, we examined response characteristics of dorsal nuclei of lateral lemniscus (DNLL) neurons of Km(Mus musculus) mice via extracellular recording to further revealed the role of DNLL neurons in auditory information processing. The effects of ascending inputs from DNLL to IC neurons were discussed by combination of acoustic stimulation and local electrical stimulation. The main results are as follows:1.96DNLL neurons were classified into two groups, transient and ongoing. The response pattern of the former was onset, and the latter included sustained, onset plus sustained as well as pauser. It suggested that DNLL neurons can process acoustic signal well via various response patterns. The two groups of neurons have significant differences in minimum threshold (MT) and dynamic range (DR)(t-test, allp<0.01). And the MT, first spike latency (FSL), DR of ongoing DNLL neurons with different response patterns were significantly different (one-way ANOVA, all p<0.001). We recorded frequency tuning curves (FTCs) of87DNLL neurons, all of them exhibited open "V" shape,79(90.8%) of them were single peak and8(9.2%) of them were double peak. There was no obvious tonotopic organization in DNLL2. Rate-intensity functions (RIFs) and FTCs of72IC neurons were recorded during local electrical stimulation of DNLL. These IC neurons could be classified into Unaffected and Inhibited according to the firing rate changes before and during stimulate DNLL. This inhibited effect depended on intervals between sound and electrical stimulations. The two types of neurons have no difference in distribution in the IC. Local electrical stimulation of DNLL increased the MT of these two types of IC neurons, and prolonged the FSL of Inhibited neurons (paired t-test, p<0.001). In addition, it also enhanced the intensity sensitivity of IC neurons, decreased the DR and increased the slope of IC neurons. Moreover, some IC neurons RIFs were also changed. And the effect was more obviously on Inhibited neurons. However, the asending inputs from DNLL didn’t affect the FTCs of IC neurons. We consider that the formation of frequency selective characteristics may mediated by other sources.In conclusion, DNLL involved in the acoustic signal feature detection of IC neurons, especially shaping the intensity-tuning.