title: Measuring hearing organ vibration patterns with confocal microscopy and optical flow.
abstract: A new method for visualizing vibrating structures is described. The system provides a means to capture very fast repeating events by relatively minor modifications to a standard confocal microscope. An acousto-optic modulator was inserted in the beam path, generating brief pulses of laser light. Images were formed by summing consecutive frames until every pixel of the resulting image had been exposed to a laser pulse. Images were analyzed using a new method for optical flow computation; it was validated through introducing artificial displacements in confocal images. Displacements in the range of 0.8 to 4 pixels were measured with 5% error or better. The lower limit for reliable motion detection was 20% of the pixel size. These methods were used for investigating the motion pattern of the vibrating hearing organ. In contrast to standard theory, we show that the organ of Corti possesses several degrees of freedom during sound-evoked vibration. Outer hair cells showed motion indicative of deformation. After acoustic overstimulation, supporting cells contracted. This slowly developing structural change was visualized during simultaneous intense sound stimulation and its speed measured with the optical flow technique.
authors.affiliation: Center for Hearing and Communication Research and Department of Otolaryngology, Karolinska Institutet, Stockholm, Sweden. anders.fridberger@cfh.ki.se
authors.forename: Anders
authors.initials: A
authors.lastname: Fridberger
authors.forename: Jerker
authors.initials: J
authors.lastname: Widengren
authors.forename: Jacques
authors.initials: J
authors.lastname: Boutet de Monvel
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000818:Animals; D046508:Culture Techniques; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006168:Guinea Pigs; D006309:Hearing / Q000502:physiology; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D018613:Microscopy, Confocal / Q000295:instrumentation* / Q000379:methods*; D009068:Movement / Q000502:physiology*; D009925:Organ of Corti / Q000166:cytology* / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014732:Vibration