Sound Localization in Birds

Klump, Georg M.

doi:10.1007/978-1-4612-1182-2_6

Cited by 105 publications

(85 citation statements)

References 134 publications

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“…The peak of a low best frequency ITD function is so broad that only a small change in rate can take place across the biological range of ITDs available to animals with small heads. Nevertheless, barn owls and other animals localize low frequency sounds well [49]. We present data on recordings from the low best frequency neurons in the barn owl nucleus laminaris that could support the hypothesis [71] that birds and mammals both use the change in rate or slope coding at low best frequencies.…”

Section: Resultssupporting

confidence: 67%

Coding interaural time differences at low best frequencies in the barn owl

Carr

Köppl

2004

Journal of Physiology-Paris

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In birds and mammals, precisely timed spikes encode the timing of acoustic stimuli, and interaural acoustic disparities propagate to binaural processing centers. The Jeffress model proposes that these projections act as delay lines to innervate an array of coincidence detectors, every element of which has a different relative delay between its ipsilateral and contralateral excitatory inputs. Thus, interaural time difference (ITD) is encoded into the position of the coincidence detector whose delay lines best cancel out the acoustic ITD. Neurons of the avian nucleus laminaris and mammalian MSO phase-lock to both monaural and binaural stimuli but respond maximally when phase-locked spikes from each side arrive simultaneously, i.e. when the difference in the conduction delays compensates for the ITD. McAlpine et al. [Nat. Neurosci. 4 (2001) 396] identified an apparent difference between avian and mammalian ITD coding. In the barn owl, the maximum firing rate appears to encode ITD. This may not be the case for the guinea pig, where the steepest region of the function relating discharge rate to interaural time delay (ITD) is close to midline for all neurons, irrespective of best frequency (BF). These data suggest that low BF ITD sensitivity in the guinea pig is mediated by detection of a change in slope of the ITD function, and not by maximum rate. We review coding of low best frequency ITDs in barn owls and mammals and discuss whether there may be differences in the code used to signal ITD in mammals and birds.

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Section: Resultssupporting

confidence: 67%

Coding interaural time differences at low best frequencies in the barn owl

Carr

Köppl

2004

Journal of Physiology-Paris

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“…If sound transmitted from the contralateral ear is strongly attenuated (i.e., the interaural transmission gain is low), the resulting directionality will be small. If the external and internal sound components have equal amplitudes, the eardrum response can range from total cancellation to a doubling of the effective sound pressure difference driving the eardrum, depending on the phase difference between direct and indirect components (Klump 2000;Feng and Christensen-Dalsgaard 2007). If the contralateral sound is attenuated by 6 dB during interaural transmission, the effect of interaural interaction ranges from −6 to 4 dB, giving the maximal directional difference of 10 dB found in frogs (Christensen-Dalsgaard 2005; Ho and Narins 2006) and birds (Larsen et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Acoustical Coupling of Lizard Eardrums

Christensen‐Dalsgaard

Manley

2008

JARO

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Lizard ears are clear examples of two-input pressuredifference receivers, with up to 40-dB differences in eardrum vibration amplitude in response to ipsi-and contralateral stimulus directions. The directionality is created by acoustical coupling of the eardrums and interaction of the direct and indirect sound components on the eardrum. The ensuing pressure-difference characteristics generate the highest directionality of any similar-sized terrestrial vertebrate ear. The aim of the present study was to measure the gain of the direct and indirect sound components in three lizard species: Anolis sagrei and Basiliscus vittatus (iguanids) and Hemidactylus frenatus (gekkonid) by laser vibrometry, using either free-field sound or a headphone and coupler for stimulation. The directivity of the ear of these lizards is pronounced in the frequency range from 2 to 5 kHz. The directivity is ovoidal, asymmetrical across the midline, but largely symmetrical across the interaural axis (i.e., front-back). Occlusion of the contralateral ear abolishes the directionality. We stimulated the two eardrums with a coupler close to the eardrum to measure the gain of the sound pathways. Within the frequency range of maximal directionality, the interaural transmission gain (compared to sound arriving directly) is close to or even exceeds unity, indicating a pronounced acoustical transparency of the lizard head and resonances in the interaural cavities. Our results show that the directionality of the lizard ear is caused by the acoustic interaction of the two eardrums. The results can be largely explained by a simple acoustical model based on an electrical analog circuit.

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“…If a sound source is moved from the median plane (azimuth angle 0 • or 180 • ) to a position on the line passing through the ears (azimuth angle 90 • or 270 • ) ITD can be expected to vary from 0 µs to 53 µs between the ears of a small songbird with a head width of 12 mm (Klump 2000). For comparison, the head width of a human adult is typically about 170 mm and the maximum ITD about 600 µs, which allows for our fine resolution of azimuth angles.…”

Section: Inaccuracy In Directional Computationmentioning

confidence: 99%

“…Judging from their reactions, birds also seem to be aware of the whereabouts of vocalizing conspecific friends and foes but the mechanisms involved and the pre-E-mail: onl@biology.sdu.dk cision, with which they perform an auditory scene analysis, are not fully understood (for references see e.g. Klump 2000).…”

Section: Introductionmentioning

confidence: 99%

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Does the environment constrain avian sound localization?

Larsen

2004

An. Acad. Bras. Ciênc.

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A bird needs to keep track not only of social interactions of conspecifics but also of their changing locations in space by determining their directions and distances. Current knowledge of accuracy in the computation of sound source location by birds is still insufficient, partly because physiological mechanisms of few species are studied in well defined laboratory settings, while field studies are performed in a variety of species and complex environments. Velocity gradients and reverberating surfaces may conceivably induce inaccuracy in sound source location (mainly elevation) by distorting the directional cues. However, most birds possess an inherently directional pressure difference receiver, which enhances the directional cues (mainly azimuth), and a computational mechanism in their auditory pathways to suppress echoes of redirected sound.

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Sound Localization in Birds

Cited by 105 publications

References 134 publications

Coding interaural time differences at low best frequencies in the barn owl

Coding interaural time differences at low best frequencies in the barn owl

Acoustical Coupling of Lizard Eardrums

Does the environment constrain avian sound localization?

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