A Dominance Hierarchy of Auditory Spatial Cues in Barn Owls

University of Lethbridge, Canada
PLoS ONE (Impact Factor: 3.23). 04/2010; 5(4):e10396. DOI: 10.1371/journal.pone.0010396
Source: PubMed


Barn owls integrate spatial information across frequency channels to localize sounds in space.
We presented barn owls with synchronous sounds that contained different bands of frequencies (3-5 kHz and 7-9 kHz) from different locations in space. When the owls were confronted with the conflicting localization cues from two synchronous sounds of equal level, their orienting responses were dominated by one of the sounds: they oriented toward the location of the low frequency sound when the sources were separated in azimuth; in contrast, they oriented toward the location of the high frequency sound when the sources were separated in elevation. We identified neural correlates of this behavioral effect in the optic tectum (OT, superior colliculus in mammals), which contains a map of auditory space and is involved in generating orienting movements to sounds. We found that low frequency cues dominate the representation of sound azimuth in the OT space map, whereas high frequency cues dominate the representation of sound elevation.
Significance: We argue that the dominance hierarchy of localization cues reflects several factors: 1) the relative amplitude of the sound providing the cue, 2) the resolution with which the auditory system measures the value of a cue, and 3) the spatial ambiguity in interpreting the cue. These same factors may contribute to the relative weighting of sound localization cues in other species, including humans.

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    • "Auditory stimuli were generated using customized Matlab software interfaced with Tucker Davis Technologies hardware (RP2). Sounds were filtered with head-related transfer functions from a typical barn owl (Witten et al. 2010) and delivered binaurally through matched earphones (ED-1914; Knowles Electronics, Itasca, IL) coupled to damping assemblies (BF-1743) inserted into the ear canals ϳ5 mm from the eardrums. The amplitudes of the two earphones were equalized to within Ϯ 2 dB. "
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