A VLSI model of range-tuned neurons in the bat echolocation system

The neural computations that support bat echolocation are of great interest to both neuroscientists and engineers, due to the complex and extremely time-constrained nature of the problem and its potential for application to engineered systems. In various areas of the bat´s brain, there exist neural circuits that are sensitive to the specific difference in time between the outgoing sonar vocalization and the returning echo, or time-of-flight. While some of the details of the neural mechanisms are known to be species-specific, a basic model of re-afference triggered, post-inhibitory rebound timing is reasonably well supported by the available data. We have designed low-power neuromorphic VLSI circuits to mimic this mechanism and have demonstrated range-dependent outputs for use in a real time sonar system. These circuits are being used to implement range-dependent vocalization rates and amplitudes.