1. Hearing and echolocation
Human hearing
Adaptations for hearing in bats
Outer ear
Middle ear
Inner ear
Auditory pathways

2. The human ear
Next slide

3. Human cochlea

4. Hair cell damage

5. Frequency detection in the cochlea

6. Hearing is tuned to echolocation: How?
CF bats
are tuned
to dominant
frequency
FM bats
show broad
frequency
sensitivity

7. Ear pinna amplifies selected frequencies
- Pinna acts as a horn
- Larger pinna transmit lower
frequencies better
- Wavelength of the resonant
frequency equals 4 x length
of the ear canal

9. Middle ear adaptations
Tympanum:oval window area = 53:1 in Tadarida, 35:1 in a cat
Malleus:incus = 3-5:1 in bats, 1.5:1 in a cat

10. Ear tympanum speed
Faster at high frequencies because it is much thinner

11. Inner ear (cochlea) adaptations
Basilar membrane is
longer and thicker at
base
A basilar membrane that is thicker at the base increases sensitivity to high frequencies

12. Rhinolophus ferrumequinum

13. The auditory pathway

14. Tonotopic map in the auditory system
Auditory cortex
Auditory cortex is expanded at frequencies associated with echolocation
Gray areas correspond to call frequencies

15. Tonotopic representation varies by species
Open space
Tonotopic representation varies by species
Blood feeder
Ground gleaner
Inferior colliculus
frequency maps

16. Neuronal tuning in horseshoe bats
Q10 = best freq/ bandwidth at -10 dB

17. Pteronotus parnellii

18. Information decoded from echos
Range
pulse-echo time delay
Velocity
pulse-echo frequency change
Target size
frequency of echo
Location
ear amplitude difference

19. Combination-sensitive neurons encode range and velocity in CF bats

20. Cortical maps vary by species