Schoffelen RL et al. (2008), Mechanics of the exceptional anuran ear.

XB-ART-59894

J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2008 May 01;1945:417-28. doi: 10.1007/s00359-008-0327-1.

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Mechanics of the exceptional anuran ear.

Schoffelen RL, Segenhout JM, van Dijk P.

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The anuran ear is frequently used for studying fundamental properties of vertebrate auditory systems. This is due to its unique anatomical features, most prominently the lack of a basilar membrane and the presence of two dedicated acoustic end organs, the basilar papilla and the amphibian papilla. Our current anatomical and functional knowledge implies that three distinct regions can be identified within these two organs. The basilar papilla functions as a single auditory filter. The low-frequency portion of the amphibian papilla is an electrically tuned, tonotopically organized auditory end organ. The high-frequency portion of the amphibian papilla is mechanically tuned and tonotopically organized, and it emits spontaneous otoacoustic emissions. This high-frequency portion of the amphibian papilla shows a remarkable, functional resemblance to the mammalian cochlea.

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Species referenced: Xenopus laevis

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	Fig. 1 Schematic drawing of a transverse section through the frog ear (adapted from Wever 1985). The division into the middle, and inner ear is indicated above the image; a selection of features is indicated in the image. The colored arrows indicate the paths of vibrational energy: green arrows represent the columellar path, red arrows the putative opercular path, and blue arrows indicate the path through the inner ear after combination of the columellar and opercular paths. The grey areas represents endolympatic fluid, dark yellow perilymphatic fluid. The green areas indicate the tectorial membranes in the papillae. (Color figure is available in the online version)
	Fig. 2 Schematic drawing of the amphibian papilla of the bullfrog, Rana catesbeiana, (adapted from Lewis et al. 1982), rotated to match orientation of Fig. 1). TM Tectorial membrane, AP amphibian papilla. a General overview of the AP; the dashed outline indicates the location of the sensory epithelium, b hair cell orientation in the sensory epithelium; dashed line indicates the position of the tectorial curtain. The numbers along the perimeter indicate the characteristic frequency of the auditory nerve fibers connecting to that site (in Hz)
	Fig. 3 Overview of measurements of the frog inner ear; comparison between Rana (left) and Hyla (right). The dashed lines indicate the separation between the amphibian papilla and the basilar papilla. a, b Distributions of characteristic frequencies of auditory nerve fibers in Rana pipiens pipiens, and Hyla cinerea. c Example of the response of the contact membrane in R. catesbeiana; black line represents the amphibian papilla, open markers the basilar papilla. d, e Distributions of spontaneous otoacoustic emissions in ranid species (combined data from R. pipiens pipiens and R. esculenta), and hylid species (combined data from H. cinerea, H. chrysoscelis, and H. versicolor). f Example of stimulus frequency otoacoustic emissions in R. pipiens pipiens at indicated stimulus levels. g, h Examples of DP-grams measured in Rana pipiens pipiens, and Hyla cinerea. a, b, d, e, g and h are taken from Van Dijk and Meenderink (2006). There they were reproduced from Ronken (1990), Capranica and Moffat (1983), Van Dijk et al. (1989, 1996), Meenderink and Van Dijk (2004), and Van Dijk and Manley (2001), respectively. c is taken from Purgue and Narins (2000a), and f is an adapted presentation of data from Meenderink and Narins (2006) (graph created with data provided by Dr. Meenderink)
	Fig. 4 Tuning curves measured in the auditory nerve in R. catesbeiana (unpublished measurements by JMS & PvD, 1992; various specimens). The numbers in the graph indicate 𝑄10dB values
	Fig. 5 Comparison of the filter quality factor 𝑄10dB versus the characteristic frequency (CF, in kHz) of nerve fibers from the cat cochlea (adapted from Evans 1975) and the leopard frog (adapted from Ronken 1991). In the leopard frog graph, the triangular symbols correspond to nerve fibers from the amphibian papilla; the circles to fibers from the basilar papilla. The black line indicates the upper limit of the amphibian papilla’s frequency domain. The grey area in the upper (cat) graph corresponds to the area of the lower (frog) graph. The loops indicate the approximate perimeter of the fiber populations in the lower graph for the amphibian papilla and the basilar papilla.

References [+] :

Benedix, Temperature dependence of two-tone rate suppression in the northern leopard frog, Rana pipiens pipiens. 1994, Pubmed