Email updates

Keep up to date with the latest news and content from BMC Neuroscience and BioMed Central.

This article is part of the supplement: Eighteenth Annual Computational Neuroscience Meeting: CNS*2009

Open Access Poster presentation

Enhancement of signal detection properties by coupling of active hair bundles

Kai Dierkes*, Benjamin Lindner and Frank Jülicher

Author Affiliations

Max Planck Institute For The Physics Of Complex Systems, Nöthnitzer Str. 38, 01187 Dresden, Germany

For all author emails, please log on.

BMC Neuroscience 2009, 10(Suppl 1):P315  doi:10.1186/1471-2202-10-S1-P315


The electronic version of this article is the complete one and can be found online at: http://www.biomedcentral.com/1471-2202/10/S1/P315


Published:13 July 2009

© 2009 Dierkes et al; licensee BioMed Central Ltd.

Poster presentation

In the inner ear of vertebrates, hair bundles transduce mechanical stimuli elicited by sound waves or substrate vibrations into electrical signals. Hair bundles from the sacculus of the bullfrog have been shown to amplify weak periodic stimuli in a frequency selective manner [1]. For stronger stimuli, their responses are marked by a region of non-linear compression [2]. They can also exhibit spontaneous oscillations [3]. These features have been recognized as signatures of the cochlear amplifier. But while the gain of the cochlear amplifier is about 1000 [4], the gain of a single hair bundle is about 10. Single hair bundle dynamics thus cannot account quantitatively for the performance of the cochlear amplifier.

In many inner ear organs, hair bundles are attached to overlaying structures such as tectorial or otolithic membranes, making hair bundles elastically coupled to each other. Here we describe results concerning the effects such a coupling could have on hair bundle dynamics. In a first approach we describe coupling by linear springs. We describe single hair bundle dynamics by means of a biophysical model that has been shown earlier to capture quantitatively the main features of stochastic hair bundle motility [5].

Our simulations show that coupling could, indeed, alter the spectral characteristics of spontaneous movements, rendering stochastic oscillations more coherent [6]. Also, coupled hair bundles can synchronize [6]. As far as signal detection properties are concerned, we find that sensitivity to weak periodic driving and frequency tuning are considerably enhanced when the strength of coupling is chosen in an appropriate way [6].

References

  1. Martin P, Hudspeth AJ: Active hair-bundle movements can amplify a hair cell's response to oscillatory mechanical stimuli.

    Proc Natl Acad Sci 1999, 96:14306-14311. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL

  2. Martin P, Hudspeth AJ: Compressive nonlinearity in the hair bundle's active response to mechanical stimulation.

    Proc Natl Acad Sci 2001, 98:14386-14391. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL

  3. Martin P, Bozovic D, Choe Y, Hudspeth AJ: Spontaneous oscillation by hair bundles of the bullfrog's sacculus.

    J Neuroscience 2003, 23:4533-4548. OpenURL

  4. Robles L, Ruggero MA: Mechanics of the mammalian cochlea.

    Physical Reviews 2001, 81:1305-1352. OpenURL

  5. Nadrowski B, Martin P, Jülicher F: Active hair-bundle motility harnesses noise to operate near an optimum of mechanosensitivity.

    Proc Natl Acad Sci 2004, 101:12195-12200. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL

  6. Dierkes K, Lindner B, Jülicher F: Enhancement of sensitivity gain and frequency tuning by coupling of active hair bundles.

    Proc Natl Acad Sci 2008, 105:18669-18674. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL