Research ReportInterdependent effects of sound duration and amplitude on neuronal onset response in mice inferior colliculus

- Duration and/or amplitude tunings are found on IC onset response neurons.
- The sound amplitude and duration have interdependent effects on the neuronal spike counts responses.
- First spike latency and duration threshold for the iso-duration stimulus vary along with the sound levels in a similar way.
- The interdependent amplitude-duration effects on the first spike latency are actually on the part of the duration threshold.

In this study, we adopted iso-frequency pure tone bursts to investigate the interdependent effects of sound amplitude/intensity and duration on mice inferior colliculus (IC) neuronal onset responses. On the majority of the sampled neurons (n=57, 89.1%), sound amplitude and duration had effects on the neuronal response to each other by showing complex changes of the rat-intensity function/duration selectivity types and/or best amplitudes (BAs)/durations (BDs), evaluated by spike counts. These results suggested that the balance between the excitatory and inhibitory inputs set by one acoustic parameter, amplitude or duration, affected the neuronal spike counts responses to the other. Neuronal duration selectivity types were altered easily by the low-amplitude sounds while the changes of rate-intensity function types had no obvious preferred stimulus durations. However, the first spike latencies (FSLs) of the onset response neurons were relative stable to iso-amplitude sound durations and changing systematically along with the sound levels. The superimposition of FSL and duration threshold (DT) as a function of stimulus amplitude after normalization indicated that the effects of the sound levels on FSLs are considered on DT actually.