Research paper
Sound localization in the alligator
Highlights
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- Physiological and behavioral data support sound localization in crocodilians.
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- Directional hearing is affected by skull pneumaticity and coupled eardrums.
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- Evolutionary changes in middle-ear pneumaticity affect localization cues.
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- Changes in auditory periphery may be reflected in neuroanatomical circuitry.
Abstract
In
early tetrapods, it is assumed that the tympana were acoustically
coupled through the pharynx and therefore inherently directional, acting
as pressure difference receivers. The later closure of the middle ear
cavity in turtles, archosaurs, and mammals is a derived condition, and
would have changed the ear by decoupling the tympana. Isolation of the
middle ears would then have led to selection for structural and neural
strategies to compute sound source localization in both archosaurs and
mammalian ancestors. In the archosaurs (birds and crocodilians) the
presence of air spaces in the skull provided connections between the
ears that have been exploited to improve directional hearing, while
neural circuits mediating sound localization are well developed. In this
review, we will focus primarily on directional hearing in crocodilians,
where vocalization and sound localization are thought to be
ecologically important, and indicate important issues still awaiting
resolution.
This article is part of a Special Issue entitled < Annual Reviews 2015 >.
Keywords
- Archosaur;
- Auditory periphery;
- Pressure-difference receiver;
- Behaving alligator;
- Skull anatomy;
- Brainstem physiology
List of Abbreviations
- ABR, auditory brainstem response;
- EPSP, excitatory postsynaptic potential;
- HRTF, head-related transfer function;
- ILD, interaural level difference;
- ITD, interaural time difference
Copyright © 2015 Elsevier B.V. All rights reserved.
