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Synchronization of Spontaneous Active Motility of Hair Cell Bundles.

Zhang TY, Ji S, Bozovic D - PLoS ONE (2015)

Bottom Line: Hair cells of the inner ear exhibit an active process, believed to be crucial for achieving the sensitivity of auditory and vestibular detection.Hair bundles are coupled by overlying membranes in vivo; hence, explaining the potential role of innate bundle motility in the generation of otoacoustic emissions requires an understanding of the effects of coupling on the active bundle dynamics.The frequency of synchronized oscillation was found to be near the mean of the innate frequencies of individual bundles.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California, United States of America.

ABSTRACT
Hair cells of the inner ear exhibit an active process, believed to be crucial for achieving the sensitivity of auditory and vestibular detection. One of the manifestations of the active process is the occurrence of spontaneous hair bundle oscillations in vitro. Hair bundles are coupled by overlying membranes in vivo; hence, explaining the potential role of innate bundle motility in the generation of otoacoustic emissions requires an understanding of the effects of coupling on the active bundle dynamics. We used microbeads to connect small groups of hair cell bundles, using in vitro preparations that maintain their innate oscillations. Our experiments demonstrate robust synchronization of spontaneous oscillations, with either 1:1 or multi-mode phase-locking. The frequency of synchronized oscillation was found to be near the mean of the innate frequencies of individual bundles. Coupling also led to an improved regularity of entrained oscillations, demonstrated by an increase in the quality factor.

No MeSH data available.


High-order mode-locking.(A) Traces of motion for a hair bundle and bead pair, showing 3:1 mode locking. Scale bar x = 200 ms, y = 30 nm. (B) Traces of motion for a bundle and bead pair, with 2:1 mode locking. Scale bar x = 100 ms, y = 30 nm. (C) The unwrapped phase of the pair shown in part A. Instantaneous phase of the bundle (Φbundle) increases faster than that of the overlying bead (Φbead). Multiplying Φbead by 3 leads to a largely parallel evolution of the phases with time. Scale bar x = 300 ms, y = 50 rad. (D) The unwrapped phase of the pair shown in part B. Multiplying Φbead by 2 leads to a largely parallel evolution of the two phases with time. Scale bar x = 200 ms, y = 20 rad.
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pone.0141764.g004: High-order mode-locking.(A) Traces of motion for a hair bundle and bead pair, showing 3:1 mode locking. Scale bar x = 200 ms, y = 30 nm. (B) Traces of motion for a bundle and bead pair, with 2:1 mode locking. Scale bar x = 100 ms, y = 30 nm. (C) The unwrapped phase of the pair shown in part A. Instantaneous phase of the bundle (Φbundle) increases faster than that of the overlying bead (Φbead). Multiplying Φbead by 3 leads to a largely parallel evolution of the phases with time. Scale bar x = 300 ms, y = 50 rad. (D) The unwrapped phase of the pair shown in part B. Multiplying Φbead by 2 leads to a largely parallel evolution of the two phases with time. Scale bar x = 200 ms, y = 20 rad.

Mentions: Mode-locking in 1:1 ratio of frequencies, as illustrated in the traces of bundle motion shown in Fig 1, was observed in clusters of up to three hair bundles. In instances where four cells synchronized their motion, one bundle in the coupled group was found to exhibit high-order mode-locking. Fig 4 shows two examples, with overlaid traces demonstrating multi-mode phase-locking: Fig 4A shows a hair bundle whose oscillation mode-locked to that of the bead in a 3:1 ratio of frequencies, with intermittent flicker to other mode-locking ratios. Fig 4B shows an example of 2:1 mode-locking. For bundles that exhibited high-order entrainment, the correlation coefficients between their active motility and the motion of the bead were found to be lower than for 1:1 entrainment, between 0.4–0.6.


Synchronization of Spontaneous Active Motility of Hair Cell Bundles.

Zhang TY, Ji S, Bozovic D - PLoS ONE (2015)

High-order mode-locking.(A) Traces of motion for a hair bundle and bead pair, showing 3:1 mode locking. Scale bar x = 200 ms, y = 30 nm. (B) Traces of motion for a bundle and bead pair, with 2:1 mode locking. Scale bar x = 100 ms, y = 30 nm. (C) The unwrapped phase of the pair shown in part A. Instantaneous phase of the bundle (Φbundle) increases faster than that of the overlying bead (Φbead). Multiplying Φbead by 3 leads to a largely parallel evolution of the phases with time. Scale bar x = 300 ms, y = 50 rad. (D) The unwrapped phase of the pair shown in part B. Multiplying Φbead by 2 leads to a largely parallel evolution of the two phases with time. Scale bar x = 200 ms, y = 20 rad.
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Related In: Results  -  Collection

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pone.0141764.g004: High-order mode-locking.(A) Traces of motion for a hair bundle and bead pair, showing 3:1 mode locking. Scale bar x = 200 ms, y = 30 nm. (B) Traces of motion for a bundle and bead pair, with 2:1 mode locking. Scale bar x = 100 ms, y = 30 nm. (C) The unwrapped phase of the pair shown in part A. Instantaneous phase of the bundle (Φbundle) increases faster than that of the overlying bead (Φbead). Multiplying Φbead by 3 leads to a largely parallel evolution of the phases with time. Scale bar x = 300 ms, y = 50 rad. (D) The unwrapped phase of the pair shown in part B. Multiplying Φbead by 2 leads to a largely parallel evolution of the two phases with time. Scale bar x = 200 ms, y = 20 rad.
Mentions: Mode-locking in 1:1 ratio of frequencies, as illustrated in the traces of bundle motion shown in Fig 1, was observed in clusters of up to three hair bundles. In instances where four cells synchronized their motion, one bundle in the coupled group was found to exhibit high-order mode-locking. Fig 4 shows two examples, with overlaid traces demonstrating multi-mode phase-locking: Fig 4A shows a hair bundle whose oscillation mode-locked to that of the bead in a 3:1 ratio of frequencies, with intermittent flicker to other mode-locking ratios. Fig 4B shows an example of 2:1 mode-locking. For bundles that exhibited high-order entrainment, the correlation coefficients between their active motility and the motion of the bead were found to be lower than for 1:1 entrainment, between 0.4–0.6.

Bottom Line: Hair cells of the inner ear exhibit an active process, believed to be crucial for achieving the sensitivity of auditory and vestibular detection.Hair bundles are coupled by overlying membranes in vivo; hence, explaining the potential role of innate bundle motility in the generation of otoacoustic emissions requires an understanding of the effects of coupling on the active bundle dynamics.The frequency of synchronized oscillation was found to be near the mean of the innate frequencies of individual bundles.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California, United States of America.

ABSTRACT
Hair cells of the inner ear exhibit an active process, believed to be crucial for achieving the sensitivity of auditory and vestibular detection. One of the manifestations of the active process is the occurrence of spontaneous hair bundle oscillations in vitro. Hair bundles are coupled by overlying membranes in vivo; hence, explaining the potential role of innate bundle motility in the generation of otoacoustic emissions requires an understanding of the effects of coupling on the active bundle dynamics. We used microbeads to connect small groups of hair cell bundles, using in vitro preparations that maintain their innate oscillations. Our experiments demonstrate robust synchronization of spontaneous oscillations, with either 1:1 or multi-mode phase-locking. The frequency of synchronized oscillation was found to be near the mean of the innate frequencies of individual bundles. Coupling also led to an improved regularity of entrained oscillations, demonstrated by an increase in the quality factor.

No MeSH data available.