Auditory cortical responses in the cat to sounds that produce spatial illusions

Humans and cats can localize a sound source accurately if its spectrum is fairly broad and flat1,2,3, as is typical of most natural sounds. However, if sounds are filtered to reduce the width of the spectrum, they result in illusions of sources that are very different from the actual locations, particularly in the up/down and front/back dimensions4,5,6. Such illusions reveal that the auditory system relies on specific characteristics of sound spectra to obtain cues for localization7. In the auditory cortex of cats, temporal firing patterns of neurons can signal the locations of broad-band sounds8,9. Here we show that such spike patterns systematically mislocalize sounds that have been passed through a narrow-band filter. Both correct and incorrect locations signalled by neurons can be predicted quantitatively by a model of spectral processing that also predicts correct and incorrect localization judgements by human listeners6. Similar cortical mechanisms, if present in humans, could underlie human auditory spatial perception.