A Novel Neural Coding Mechanism Study of Interaural Time Difference Detection

Interaural time difference (ITD) detection plays a critical role in sound localization. Some neurophysiology experiments found that the ITD discrimination threshold for single neuron in medial superior olive (MSO) is about 20 mu s. In order to reveal the ITD coding mechanism essentially, an ITD detection model has been proposed in this paper based on the anatomical structure of the mammalian auditory system. Most previous research only discuss the relationship between the ITDs and the spike rate of the MSO neuron. In these results, the spike rate difference is under 1 spike/s when the ITD changes in 20 mu s. It means the neuron needsmore than 1 s to distinguish the ITD by spike rate coding. This explanation contradicts with the rapid and accurate sound localization response in animal psychoacoustics experiments. In our study, the neural coding in ITD detection model has been investigated via the approach of circle maps and symbolic dynamics. With these two methods, the ITDs under 20 mu s can be detected in 1 s. This neural coding hypothesis agrees with the ITD detection response time in the animal behavior experiments.