A Neuromorphic VLSI Model of Bat Interaural Level Difference Processing for Azimuthal Echolocation

Bats use the unusual sensory modality of echolocation to fly in complete darkness with speed and agility through complex three-dimensional environments. Their small head size and the use of high-frequency sound make interaural level differences (ILDs) their primary cue for azimuthal echolocation. In this paper, we present a neuromorphic VLSI-based system that emulates the ILD processing in the bat brainstem and midbrain. By selecting simple neural units, we propose a circuit model that is mathematically tractable and captures the essential elements of bat ILD computation. The chip includes a three-layer network of spiking neurons with 32 neurons on each layer, and the address-event representation for external interface. Emphasizing the neural spike timing and population behavior, we hope this study will contribute to the bat research community in particular as well as neuroscience in general by providing a real-time, fine-grained, neuromorphic bat echolocation simulator that will be used to address system-level performance of low-level neural algorithms. By developing functional models of the bat echolocation system, we hope to emulate the efficient implementation demonstrated by nature