The role of spectral composition of sounds on the localization of sound sources by cats 1 2 3

33 Sound localization along the azimuthal dimension depends on interaural time and level 34 disparities, while localization in elevation depends on broadband power spectra resulting from 35 the filtering properties of the head and pinnae. We trained cats with their heads unrestrained 36 using operant conditioning to indicate the apparent locations of sounds via gaze shift. Targets 37 consisted of broadband (BB), high pass (HP) or low pass (LP) noise, tones from .5 to 14 kHz and 38 1/6 octave narrow band (NB) noise with center frequencies ranging from 6 to 16 kHz. For each 39 sound type, localization performance was summarized by the slope of the regression relating 40 actual gaze shift to desired gaze shift. Overall localization accuracy for BB noise was 41 comparable in azimuth and in elevation, but markedly better in azimuth than in elevation for 42 sounds with limited spectra. Gaze shifts to targets in azimuth were most accurate to BB, less 43 accurate for HP, LP and NB sounds and considerably less accurate for tones. In elevation, cats 44 were most accurate in localizing BB, somewhat less accurate to HP, and less yet to LP noise 45 (though still with slopes ~0.60), but they localized NB noise much worse and were unable to 46 localize tones. Deterioration of localization as bandwidth narrows is consistent with the 47 hypothesis that spectral information is critical for sound localization in elevation. For NB noise 48 or tones in elevation, unlike humans, most cats did not have unique responses at different 49 frequencies and some appeared to respond with a “default” location at all frequencies. 50