A VLSI model of the bat dorsal nucleus of the lateral lemniscus for azimuthal echolocation

The dorsal nucleus of the lateral lemniscus (DNLL) is a distinct group of auditory cells that play a strategic role in azimuthal echolocation in the bat. Dominated by EI-type cells that receive excitation from the contralateral ear and inhibition from the ipsilateral ear, the DNLL processes interaural level difference (ILD) information by integrating inputs from lower brainstem areas and projecting its outputs to the midbrain. In this paper, we propose a two layer recurrent spiking neural network model that simulates ILD processing by the DNLL, and present a VLSI implementation using the address-event representation (AER) protocol. We demonstrate, using this neuromorphic VLSI-based hardware system, that long-lasting inhibition in the DNLL can alter its spatial selectivity to multiple sounds (objects).