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K +. The Odditory System . AIR. amplification. FLUID. Harry Hair-Cell: Official Cochlea Mascot. Be careful, the frequency tuning isn’t linear!. Inner hair cells. Each tuned to a ‘best’ frequency. Outer hair cells. Provide ‘frequency specific’ amplification. Basilar Membrane.

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Presentation Transcript
slide1

K+

The Odditory System

AIR

amplification

FLUID

Harry Hair-Cell: Official Cochlea Mascot

slide2

Be careful, the frequency tuning isn’t linear!

Inner hair cells.

Each tuned to a ‘best’ frequency.

Outer hair cells.

Provide ‘frequency specific’ amplification.

Basilar Membrane

slide3

Frequency Spectrogram

4

Flute

3

kHz

2

1

0

Time

slide4

Frequency Spectrogram

4

Trumpet

3

kHz

2

1

0

Time

slide5

Frequency Spectrogram

Drum

4

3

kHz

2

1

0

Time

slide6

To hair cell

From sound wave

slide9

The Cochlea is Fluid-Filled

Ever Listened to Someone Talk Underwater?

You Are Right Now!

place theory of frequency encoding

33 mm

‘Place’ Theory of Frequency Encoding
  • Inner hair cells encode frequencies by Fourier Analysis
    • We’ll deal with Outer Hair Cells in a minute
  • Basilar Membrane dimensions are the key
  • narrowtowide
  • High Freq at base, Low Freq at apex
slide12

High Frequencies

A row of tiny, frequency-tuned microphones

Low Frequencies

slide13

High Frequencies

Low Frequencies

slide15

Cross-

Section View

Oval window

Round

window

slide21

Cilia Attached to

Tectorial Membrane

Outer Hair Cells

and the Cochlear Amplifier

slide22

View from Above

Cross-

Section View

Outer Hair Cells act as ‘frequency specific’ amplifiers, like an ‘equalizer’ on your stereo

slide23

K+

K+

Outer Hair Cells

and the Cochlear Amplifier

Amplifier ‘on’

Amplifier ‘off’

slide24

How does a ‘Cochlear

Implant’ work?

slide26

Right Temporal Cortex

Primary Auditory Cortex

1

2

3

4

5

6

TONOTOPIC

(it’s a map of the basilar membrane!)

Low

Hi

First we break it down . . .

Left Cochlea

(basilar membrane)

slide27

“Feature Detectors”

cells that respond to

complex auditory stimuli!

1

2

3

4

5

6

Right Temporal Cortex

Secondary Auditory Cortex

Then we put it back together!

Note: this is a hypothetical model

1

2

3

4

5

6

Right Temporal Cortex

Primary Auditory Cortex

Low

Hi

TONOTOPIC

(it’s a map of the basilar membrane!)

the mcgurk effect
The McGurk Effect
  • ‘Hearing’ with your eyes. . .
  • Generate ambiguous stimulus, with conflicting auditory and visual information
  • ‘Who’ are you going to believe?
sound localization
Sound Localization
  • Doppler Shift (monaural)
  • Interaural intensity difference (Hi only)
  • Interaural time delay
  • Interaural phase difference
slide30

Primary

Motor Cortex

Primary

Sensory Cortex

Rat

CNS

Motor output

Sensory input

Telencephalon

WHAT?

Thalamus

relay, feedback

Midbrain

WHERE?

Spinal Cord

reflexes, input, output

GENERAL Overview of Sensory System Organization

slide32

Barn Owl

crooked ears detect the ‘y’ axis

slide34

Sound Source

in Front

L R

E

A

B

C

D

Summation of inputs is key

slide35

Sound Source

on

Right side

L R

E

A

B

C

D

Summation of inputs is key

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