Simulated motion enhances neuronal selectivity for a sound localization cue in background noise

In nature, sound sources move and signals are accompanied by background noise. Noting that motion helps the perception of visual stimuli, we tested whether motion similarly facilitates the detection of acoustic targets, at the neuronal level. Auditory neurons in the central nucleus of the barn owl's inferior colliculus (ICc), due to their selectivity for interaural phase difference (delta phi), are sharply tuned to the azimuth of sound sources and are arrayed to form a topographic map of delta phi. While recording from single ICc neurons, we presented tones that simulated either moving or stationary sound sources with and without background noise. We found that the tuning of cells in the ICc for delta phi was sharper for stimuli that simulated motion than for those that simulated stationary targets. The neurons signaled the presence of a tone obscured by noise better if the tone moved than if the tone remained stationary. The resistance to noise observed with moving stimuli could not be reproduced with the temporal modulation of the stimulus amplitude, suggesting that a change of position over time was required.