Studies On The Information Processing Properties In The Neural Circuitry Of Auditory Computation Of Sound Source Localization

Auditory perception is one of the most active research topics in the 21st century of brain exploration, and how the neural information are represented and processed in the neuronal circuitry of low frequency sound localization have received considerable attention around the world. The research work here focuses on the information processing properties of both the frequency and source-source in this neural circuitry in auditory pathways.On the aspect of frequency information processing, we study the frequency characteristics of bushy cells in the ventral cochlear nucleus (VCN), and find that bushy cells exhibit frequency selectivity behaviours and the sensitive frequency range is about 40-80 Hz; this kind of frequency selectivity features of bushy cell originate from the intrinsic oscillatory properties of a cell; in addition, the sensitive frequency range among bushy cell could hardly show any difference, implying the frequency selectivity behavior of bushy cell may not be relevant to encoding of sound frequency in the cochlear nucleus of auditory system.On the aspect of rate coding for sound-source information, we show that coupling kinetics could modulate ITD tuning sensitivity of firing rate, which in turn affects the performance of sound localization; the increment of low-threshold potassium ion channel density may improve the acuteness of sound localization; inhibitory inputs can elicit spikes in the output of auditory neurons, thus may pose substantial influence on the rate coding properties of auditory system.On the aspect of timing coding for sound-source information, our results suggest that: the decrease of low-threshold potassium channel density can to some extent suppress the noise effects, which in essence results from the enhancement of the signal-to-noise ratio in the output of the nervous system; strong coupling strength along with appropriate noise intensity could introduce the phenomenon of stochastic synchronization in a globally coupled bushy cell network; the first spike latency (FSL) of auditory neurons elegantly shows linear dependence on the interaural time differences of arriving signals, indicating that FSL cues may serve as a candidate coding mechanism for sound source localization.The above conclusions help improve our understanding about how the sound frequency is represented in the auditory system, and bring us with useful insights and cues for the search of sound source coding mechanism, especially the proposal of FSL coding provide us a novel and promising cue for sound localization.