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The inner ear PICTURES FROM WIKIPEDIA COCHLEA CROSS SECTION OF THE COCHLEA
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Computational Neuroscience Lecture 7
Conor Houghton
PICTURE FROM WIKIPEDIA
The inner earPICTURES FROM WIKIPEDIA
COCHLEA
CROSS SECTIONOF THE COCHLEA
Outer hair cells amplify
http://youtube.com/ /watch?v=Xo9bwQuYrRo
• Video of dancing haircell.
Inner hair cells signal
http://youtube.com/ /watch?v= 1VmwHiRTdVc
• Video about the inner ear, with the sound removed.
Stereocilia of a frog’s inner ear
PICTURE FROM WIKIPEDIA
Different hair cells respond to different frequencies – all hair cells respond to sound over a short time window.
This gives a windowed Fourier transform.
Windowed Fourier transform
s(t)
k(t)
s(t)k(t)
Weber’s law
• Roughly speaking – effect goes like the log of the cause.
• Sort of holds for the auditory system.• Use log|S(k,t)|
• SMALL PRINT: The phase information is gone, however, we have overlapping windows and two variables; there are theorems that say we haven’t lost anything.
Spectrogram
http://youtube.com/ /watch?v= 5hcKa86WJbg
• Zebra finch song and spectrogram.
Spectrogram
http://youtube.com/ /watch?v= 5hcKa86WJbg
• Repeat of zebra finch song.
Zebra finches
http://effieex3.tumblr.com/post/20369494508
Zebra finch brain
Maybe it’s like vision?
Linear model
Error
Minimize error
Calculate the STRF
From Sen et al.J Neuro 2001
From Sen et al.J Neuro 2001
From Sen et al.J Neuro 2001
So?
• Works better than you might expect, particularly in the lower part of the pathway.
• Does not give the whole story, particularly further up the pathway.
• The calculation is hairy, but seems to work, certainly don’t try to improve it.
• The STRFs aren’t quite as revealing as you’d expect.