High-speed video analysis of acoustically oscillated Guinea pig stapes

Objective: We investigated the ossicular movement in the near-intact middle ear in response to acoustic stimulation using a high-speed video camera and video analysis software program. Design: We have designed a good visual access to the middle ear of the Guinea pig by opening the ventral wall of the otic capsule, without injuring the sound-conducting structures, from the external auditory canal to the oval window. The high-speed video camera could record analysable ossicular motion up to 4000 frames per second. Results: The stapes showed reciprocal movement in the same frequency as the stimulating tone, and with an amplitude proportional to the stimulating sound intensity. Injury to the tympanic membrane attenuated the stapedial motion, which was recovered to that of the control level by patch repair of the perforation. Conclusion: Our experimental set-up was capable of evaluating the conductive hearing, regardless of the status of the animal's sensorineural hearing or even life. Such a video analysis may provide a powerful tool to investigate the physiology of the middle ear.