A Biologically Inspired Spiking Neural Network for Sound Localisation by the Inferior Colliculus

We introduce a biologically inspired azimuthal sound localisation system, which simulates the functional organisation of the human auditory midbrain up to the inferior colliculus (IC). Supported by recent neurophysiological studies on the role of the IC and superior olivary complex (SOC) in sound processing, our system models two ascending pathways of the auditory midbrain: the ITD (Interaural Time Difference) pathway and ILD (Interaural Level Difference) pathway. In our approach to modelling the ITD pathway, we take into account Yin's finding that only a single delay line exists in the ITD processing from cochlea to SOC for the ipsilateral ear while multiple delay lines exists for the contralateral ear. The ILD pathway is modelled without varied delay lines because of neurophysiological evidence that indicates the delays along that pathway are minimal and constant. Level-locking auditory neurons are introduced for the ILD pathway network to encode sound amplitude into spike sequence, that are similar to the phase-locking auditory neurons which encode time information to the ITD pathway. A leaky integrate-and-fire spiking neural model is adapted to simulate the neurons in the SOC that process ITD and ILD. Experimental results show that our model performs sound localisation that approaches biological performance. Our approach brings not only new insight into the brain mechanism of the auditory system, but also demonstrates a practical application of sound localisation for mobile robots.