Binding Mechanism of Frequency-Specific ITD and IID Information in Sound Localization of Barn Owl

Abstract

Barn owls perform sound localization based on analyses of interaural differences in arrival time and intensity of sound. Two kinds of neural signals representing the interaural time difference (ITD) and interaural intensity difference (IID) are processed in parallel in anatomically separate pathway. The values of ITD and IID are largely changed depending on frequency components of sound. The neural circuits involved in sound localization must bind the frequency-specific ITD and IID information to determine a spatial direction of sound source. However, little is known about the binding mechanism. We present here a neural network model of ICc ls in which the signals representing ITD and IID are first combined with each other. It is shown using our model how the neural maps can be generated in ICc ls by the excitatory inputs from ICc core representing ITD and the inhibitory inputs from VLVps representing IID. We show also that ICx neuron detects a spatial direction of sound source by making synaptic connections with ICc ls neurons encoding ITD and IID information of the sound source, based on Hebbian learning.