Spike-Timing-Based Computation in Sound Localization
(A) ITD measured at 217 Hz as a function of source location. When the sound is presented at azimuth −45° and elevation −10°, the ITD is consistent with all locations shown by the solid curve. For a spherical head, this curve corresponds to the “cone of confusion”. (B) ITD measured at 297 Hz vs. source location. The pattern is similar but quantitatively different from ITDs measured at 217 Hz (A), because sound diffraction makes ITDs frequency-dependent . The ITD at location (−45°,−10°) is consistent with all locations shown by the dashed curve. (C) When the sound includes frequency components at 217 Hz and 297 Hz and ITDs can be measured in both channels, source location is unambiguously signaled by the intersection of the two level lines (green cross), corresponding to the ITD measured at the two frequencies. The red circle shows that this intersection resolves a potential front-back confusion.