The peripheral auditory system:From sound to spike

Table of Contents

The peripheral auditory system:From sound to spike

Phenomena that can be accounted for by the functioning of the auditory periphery

Three main divisions:Outer (external), Middle and Inner ear

Outer ear

Middle ear

Middle-ear movement

Middle ear

The ear

Imagine the cochlea unrolled

Cochlear cross section shows three chambers

Stand the snail on end and slice through ...

The real thing ...

Stand it on its base and look down from the top ...

A cross-section through the cochlea

Taking a closer look at the Organ of Corti

Innervation of the Organ of Corti

Horizontal innervation scheme in the cat ...

Inner ear - Structure - Organ of Corti

Inner ear - Cochlear Structure - Electron Micrograph

Inner ear - Cochlear Structure - Electron Micrographs

Pressure variations in the cochlear fluids cause the basilar membrane/Organ of Corti to move ...

… and the hair cilia to be moved, releasing neuro-transmitter from the base of the inner hair cells.

A more schematic look ...

What function do the OHCs have?

Outer hair cells can move!

Sensory transduction performed by IHCs

Basilar membrane motion to different frequency sinusoids

Other evidence concerning tonotopic maps

A tono-topic map (frequency to place)

Defining the envelope of the travelling wave

Envelopes of BM displacement at 4 different frequencies (in 4 distinct measurements)

Frequency responses obtained at 6 different places on the basilar membrane

Four aspects of firing patterns on the auditory nerve

Rate-level functions for auditory nerve fibres

However, firing rates depend not only on sinusoidal sound intensity but also on sound ...

Detour through the notion of an audiogram ...

Audiograms can also be expressed in dB SPL

The audiogram of single auditory nerve fibres

Information about stimulus frequency is not only coded by which nerve fibres are active (the place code) but also by when the fibres fire (the time code).

Neural stimulation to a low frequency tone

But this information is limited to lower frequencies ...

Enhanced response to sound onsets:The value of novelty

Summary — Part I

Summary — Part II

The End

Email: stuart@phon.ucl.ac.uk

Home Page: http://www.phon.ucl.ac.uk/home/stuart/home.htm

Note: Some of these pages contain links to movie files requiring the Apple Quicktime plug-in. If you don't have this player then follow this link to the Apple site.

Other C315 presentations