The Odditory System

1. K+ The Odditory System AIR amplification FLUID Harry Hair-Cell: Official Cochlea Mascot

2. 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

3. Frequency Spectrogram 4 Flute 3 kHz 2 1 0 Time

4. Frequency Spectrogram 4 Trumpet 3 kHz 2 1 0 Time

5. Frequency Spectrogram Drum 4 3 kHz 2 1 0 Time

6. To hair cell From sound wave

7. Two sources of ‘amplification’ in the Middle Ear

8. Two small muscles within the Middle Ear allow control over amplification.

9. The Cochlea is Fluid-Filled Ever Listened to Someone Talk Underwater? You Are Right Now!

11. 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

12. High Frequencies A row of tiny, frequency-tuned microphones Low Frequencies

13. High Frequencies Low Frequencies

15. Cross- Section View Oval window Round window

17. The World’s Smallest Microphone

18. Tugging on tip links opens K+ channels

21. Cilia Attached to Tectorial Membrane Outer Hair Cells and the Cochlear Amplifier

22. View from Above Cross- Section View Outer Hair Cells act as ‘frequency specific’ amplifiers, like an ‘equalizer’ on your stereo

23. K+ K+ Outer Hair Cells and the Cochlear Amplifier Amplifier ‘on’ Amplifier ‘off’

24. How does a ‘Cochlear Implant’ work?

26. 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)

27. “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!)

28. The McGurk Effect • ‘Hearing’ with your eyes. . . • Generate ambiguous stimulus, with conflicting auditory and visual information • ‘Who’ are you going to believe?

29. Sound Localization • Doppler Shift (monaural) • Interaural intensity difference (Hi only) • Interaural time delay • Interaural phase difference

30. 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

32. Barn Owl crooked ears detect the ‘y’ axis

33. The speed of the neural impulse is a constant value E A B C D Summation of inputs is key

34. Sound Source in Front L R E A B C D Summation of inputs is key

35. Sound Source on Right side L R E A B C D Summation of inputs is key