Animals and ICE: meaning, origin, and diversity

Hemmen, J. Leo van; Christensen‐Dalsgaard, Jakob; Carr, Catherine E.; Narins, Peter M.

doi:10.1007/s00422-016-0702-x

Cited by 25 publications

(21 citation statements)

References 36 publications

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“…Two strategies have emerged to improve localization when lowfrequency hearing and small heads limit animals' ability to encode sound source location. Other reptiles, such as lizards and archosaurs, have coupled ears, which increase the range of ITDs available at low frequencies (Calford and Piddington, 1988;Christensen-Dalsgaard and Manley, 2008;Larsen et al, 2016;van Hemmen et al, 2016). Small mammals, such as the gerbil and guinea-pig, show a trend that places the sensitive slope of the function where greatest ITD discrimination is required (McAlpine et al, 2001; for reviews see Grothe et al, 2010;Grothe and Pecka, 2014).…”

Section: Discussionmentioning

confidence: 99%

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A circuit for detection of interaural time differences in the nucleus laminaris of turtles

Willis

Carr

2017

Journal of Experimental Biology

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The physiological hearing range of turtles is approximately 50-1000 Hz, as determined by cochlear microphonics ( Wever and Vernon, 1956a). These low frequencies can constrain sound localization, particularly in red-eared slider turtles, which are freshwater turtles with small heads and isolated middle ears. To determine if these turtles were sensitive to interaural time differences (ITDs), we investigated the connections and physiology of their auditory brainstem nuclei. Tract tracing experiments showed that cranial nerve VIII bifurcated to terminate in the first-order nucleus magnocellularis (NM) and nucleus angularis (NA), and the NM projected bilaterally to the nucleus laminaris (NL). As the NL received inputs from each side, we developed an isolated head preparation to examine responses to binaural auditory stimulation. Magnocellularis and laminaris units responded to frequencies from 100 to 600 Hz, and phase-locked reliably to the auditory stimulus. Responses from the NL were binaural, and sensitive to ITD. Measures of characteristic delay revealed best ITDs around ±200 μs, and NL neurons typically had characteristic phases close to 0, consistent with binaural excitation. Thus, turtles encode ITDs within their physiological range, and their auditory brainstem nuclei have similar connections and cell types to other reptiles.

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Section: Discussionmentioning

confidence: 99%

“…The rapid Golgi technique was used on five young turtles (carapace length 2.5 cm) (Valverde, 1970). Brains were removed and placed in Golgi fixative, an aqueous solution containing 2.33% potassium dichromate and 0.19% osmium tetroxide.…”

Section: Tract Tracing and Golgimentioning

confidence: 99%

A circuit for detection of interaural time differences in the nucleus laminaris of turtles

Willis

Carr

2017

Journal of Experimental Biology

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“…We start by describing a typical situation, viz., that of internally coupled ears (ICE), which is present in more than half of the terrestrial vertebrates. Though ICE has been observed and described since long, it has attracted considerable attention only recently [37]. It is used here as a typical example from acoustics to illustrate the general idea of geometric perturbation theory.…”

Section: Introduction: Geometric Perturbation Theorymentioning

confidence: 99%

“…Whereas mammals have independent ears, which do not influence each other, most of the terrestrial vertebrates have ICE at their disposal, which means an internal, air-filled, cavity that connects the two eardrums. ICE allows in particular small animals with small head and, hence, small ITD to greatly increase its effective interaural distance; typically, for low frequencies by a multiplicative factor of 2-4 [37]. What the animal then actually perceives is the so-called the internal time difference (iTD) as the superposition of the external auditory stimulus p ext operating at the two eardrums located at, say, x = 0 and x = L, and the internal pressure p; see Fig.…”

Section: Introduction: Geometric Perturbation Theorymentioning

confidence: 99%

Geometric perturbation theory and Acoustic Boundary Condition Dynamics

Heider

Hemmen

2020

Physica D: Nonlinear Phenomena

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Geometric perturbation theory is universally needed but not recognized as such yet. A typical example is provided by the three-dimensional wave equation, widely used in acoustics. We face vibrating eardrums as binaural auditory input and stemming from an external sound source. In the setup of internally coupled ears (ICE), which are present in more than half of the land-living vertebrates, the two tympana are coupled by an internal air-filled cavity, whose geometry determines the acoustic properties of the ICE system. The eardrums themselves are described by a two-dimensional, damped, wave equation and are part of the spatial boundary conditions of the threedimensional Laplacian belonging to the wave equation in the internal cavity that couples and internally drives the eardrums. In animals with ICE the resulting signal is the superposition of external sound arriving at both eardrums and the internal pressure coupling them. This is also the typical setup for geometric perturbation theory. In the context of ICE it boils down to acoustic boundary-condition dynamics (ABCD) for the coupled dynamical system of eardrums and internal cavity. In acoustics the deviations from equilibrium are extremely small (nm range). Perturbation theory therefore seems natural and is shown to be appropriate. In doing so, we use a time-dependent perturbation theoryà la Dirac in the context of Duhamel's principle. The relaxation dynamics of the tympanic-membrane system, which neuronal information processing stems from, is explicitly obtained in first order. Furthermore, both the initial and the quasi-stationary asymptotic state

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“…To achieve their remarkable directional sensitivity crickets, like many other small animals with good directional hearing, have evolved specialized internal air-filled pathways between the left and right tympanal membranes [24][25][26]. Cricket ears are located on the proximal part of their prothoracic tibias.…”

Section: Introductionmentioning

confidence: 99%

Frequency tuning and directional sensitivity of tympanal vibrations in the field cricketGryllus bimaculatus

Lankheet

Cerkvenik

Larsen

et al. 2017

J. R. Soc. Interface.

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Female field crickets use phonotaxis to locate males by their calling song. Male song production and female behavioural sensitivity form a pair of matched frequency filters, which in Gryllus bimaculatus are tuned to a frequency of about 4.7 kHz. Directional sensitivity is supported by an elaborate system of acoustic tracheae, which make the ears function as pressure difference receivers. As a result, phase differences between left and right sound inputs are transformed into vibration amplitude differences. Here we critically tested the hypothesis that acoustic properties of internal transmissions play a major role in tuning directional sensitivity to the calling song frequency, by measuring tympanal vibrations as a function of sound direction and frequency. Rather than sharp frequency tuning of directional sensitivity corresponding to the calling song, we found broad frequency tuning, with optima shifted to higher frequencies. These findings agree with predictions from a vector summation model for combining external and internal sounds. We show that the model provides robust directional sensitivity that is, however, broadly tuned with an optimum well above the calling song frequency. We therefore advocate that additional filtering, e.g. at a higher (neuronal) level, significantly contributes to frequency tuning of directional sensitivity.

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Animals and ICE: meaning, origin, and diversity

Cited by 25 publications

References 36 publications

A circuit for detection of interaural time differences in the nucleus laminaris of turtles

A circuit for detection of interaural time differences in the nucleus laminaris of turtles

Geometric perturbation theory and Acoustic Boundary Condition Dynamics

Frequency tuning and directional sensitivity of tympanal vibrations in the field cricketGryllus bimaculatus

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