CAS PS 222 Lecture Notes - Lecture 12: Spiral Ganglion, Ganglion Cell, Hair Cell
18 May 2018
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Inner Hair cells transduce and send the signal to the brain via the Spiral Ganglion cells.
The axons of the spiral ganglion cells make up the Auditory nerve.
Amplitude Coding:
Amplitude is coded on the group fiber level. We can read amplitude from groups of auditory
nerve fibers responding which get info from inner hair cells.
As the amplitude of the sound increases, more and more neighboring fibers will respond.
In the graph: Each of the line represents the response of an auditory nerve fiber.
Auditory threshold: How much amplitude is required for a response.
The bottom of the curves represents the cells preferred stimulus. It takes very little amplitude
for e.g. C to respond to a stimulus of a 1000 Hz.
But as you increase the amplitude of the stimulus, in a 500 Hz tone, auditory nerve fiber B is the
only one responding at 40 dB.
Now up at 52 dB, not only is B responding, but even A and C are responding. The coincidence of
these three nerve fibers responding to this is indicative of the 500 hertz tone at 50 dB.
So groups of nerve fibers responding together code for the amplitude of the stimulus.
As you increase the amplitude, you increase the likelihood that more and more neighboring fibers
are going to respond.
How is waveform coded?
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Document Summary
Inner hair cells transduce and send the signal to the brain via the spiral ganglion cells. The axons of the spiral ganglion cells make up the auditory nerve. Amplitude is coded on the group fiber level. We can read amplitude from groups of auditory nerve fibers responding which get info from inner hair cells. As the amplitude of the sound increases, more and more neighboring fibers will respond. In the graph: each of the line represents the response of an auditory nerve fiber. Auditory threshold: how much amplitude is required for a response. The bottom of the curves represents the cells preferred stimulus. It takes very little amplitude for e. g. c to respond to a stimulus of a 1000 hz. But as you increase the amplitude of the stimulus, in a 500 hz tone, auditory nerve fiber b is the only one responding at 40 db.
