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Home , Audiology

Columbia University Department of Otolaryngology/Head and Neck Surgery

Listen Up! A Free Public Forum on and the Treatment of

1 sound pressure waves

pass through the

vibration

Middle ear vibration

fluid/tissue traveling wave in the Cochlea apex Fluid compartments: sensory tissue:

Auditory plunges in Base Apex nerve and out of cochlea at the base Human Cochlea is ~ 0.5cm wide auditory and “uncoiled” is ~ 3.5cm long. nerve

Cross-section of cochlea base The cochlea is like a fluid-filled hose, coiled around a central cylinder, with a partition that splits the hose lengthwise. The partition contains the sensory tissue (organ of Corti). 3 auditory nerve

Cross-section of cochlea The cochlea is like a fluid-filled hose, coiled around a central cylinder, with a partition that splits the hose lengthwise. The partition contains the sensory tissue (organ of Corti). 4 Sensory Tissue of the ear: Organ of Corti Single cross-section Extended cross-section

“hair” =

outer hair cells Stereocilia (“hair”) inner

20 µm Auditory 0.1 mm neurons

Image: Pujol R. Anatomie et physiologie de la cochlée. Arch Int Phys Bioch , 97-4, 1989; http://www.iurc.montp.inserm.fr/cric/audition Motions within the organ of Corti stretch tip links between the “hairs”, opening&closing ion channels, modulating hair cell voltage, modulating neurotransmitter release to the auditory neurons and ultimately … HEARING “Uncoil” the cochlea to schematize / analyze the motion The sensory tissue vibrates up&down as a wave that peaks part way along the cochlea. High frequencies peak in the base, low frequencies peak in the apex. This is called “tonotopic tuning.”

Stapes

Stapes Chamber depth ~ 0.1mm Normal wave height << 1micrometer Round window base apex

Singing glass (Freesounds.org) Man sings lololo (freesound.org) Outer Hair cells exert forces that pump up the motion at the peak of the traveling wave, like a kid pumping a swing. This is called the cochlear amplifier. Pumped-up region

The cochlear amplifier makes the motion larger, AND greatly improves the resolution. This enhances the ability of the ear to resolve different frequencies, and thus resolve different sounds.

7 http://freesound.org/people/klankbeeld/ Outer hair cells can be damaged, leading to impaired hearing.

Visual analogy: In a damaged or aged cochlea in which the cochlear amplifier is not functioning, in addition to reducing the size of the cochlear motions, the frequency resolution is diminished, and the patterned response on the sensory tissue becomes “unfocussed.”

8 An external sends an amplified sound to the entire cochlea, thus increases the size of the stimulus but cannot improve the focus.

9 Because of the local action of cochlear amplification, “There is no such thing as eye-glasses for the ear”

10 Outer Ear Middle Ear

inner hair cell outer hair cells

20 µm Auditory neurons

Cochlea

Hearing impairment can also be due to loss or damage to inner hair cells, auditory neurons, and the eardrum and ossicles (middle ear). Hearing impairment can also be due to faulty processing in the brainstem and brain (e.g., ). 11 Many things can cause hearing impairment Genetic Background

Illness and treatments for illness

Aging Noise Damage

12 Program and Speakers:

9:30 Welcome and Introduction 10:30 Future treatment for Hearing Loss Elizabeth Olson, PhD Justin Golub, MD Associate Professor, Otolaryngology Assistant Professor, Otolaryngology / and Biomedical Engineering Head and Neck Surgery

9:45 Available Technology for the Hearing 10:50 Perspectives of a Hearing Aid User Impaired Richard Einhorn Megan Kuhlmey, Au.D. Composer and Musician Assistant Professor of Audiology Board Member, Hearing Loss Assoc. of America 10:05 Medical and Surgical Treatment 11:15 Ana Kim, MD • Q&A Associate Professor Otolaryngology / • Meet the speakers Head and Neck Surgery • Cookies and Coffee Co-director of • Audiological Screening/Sign-up for Program Screening on March 23

Thank you to Ilana Cellum, Inge Goldstein 13