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.