Download - Computational Neuroscience Lecture 7
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Computational Neuroscience Lecture 7
Conor Houghton
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PICTURE FROM WIKIPEDIA
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The inner earPICTURES FROM WIKIPEDIA
COCHLEA
CROSS SECTIONOF THE COCHLEA
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Outer hair cells amplify
http://youtube.com/ /watch?v=Xo9bwQuYrRo
• Video of dancing haircell.
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Inner hair cells signal
http://youtube.com/ /watch?v= 1VmwHiRTdVc
• Video about the inner ear, with the sound removed.
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Stereocilia of a frog’s inner ear
PICTURE FROM WIKIPEDIA
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Different hair cells respond to different frequencies – all hair cells respond to sound over a short time window.
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This gives a windowed Fourier transform.
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Windowed Fourier transform
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s(t)
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k(t)
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s(t)k(t)
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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.
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Spectrogram
http://youtube.com/ /watch?v= 5hcKa86WJbg
• Zebra finch song and spectrogram.
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Spectrogram
http://youtube.com/ /watch?v= 5hcKa86WJbg
• Repeat of zebra finch song.
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Zebra finches
http://effieex3.tumblr.com/post/20369494508
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Zebra finch brain
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Maybe it’s like vision?
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Linear model
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Error
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Minimize error
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Calculate the STRF
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From Sen et al.J Neuro 2001
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From Sen et al.J Neuro 2001
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From Sen et al.J Neuro 2001
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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.